Commit Graph

186 Commits

Author SHA1 Message Date
Juergen Gross 7a048cec59 xen: drop writing error messages to xenstore
xenbus_va_dev_error() will try to write error messages to Xenstore
under the error/<dev-name>/error node (with <dev-name> something like
"device/vbd/51872"). This will fail normally and another message
about this failure is added to dmesg.

I believe this is a remnant from very ancient times, as it was added
in the first pvops rush of commits in 2007.

So remove the additional message when writing to Xenstore failed as
a minimum step.

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracel.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
2018-10-26 09:17:16 +02:00
Joe Jin 076e2cedd6 xen: export device state to sysfs
Export device state to sysfs to allow for easier get device state.

Signed-off-by: Joe Jin <joe.jin@oracle.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
2018-08-28 17:37:40 -04:00
Roger Pau Monne 515e6541f5 xen/store: do not store local values in xen_start_info
There's no need to store the xenstore page or event channel in
xen_start_info if they are locally initialized.

This also fixes PVH local xenstore initialization due to the lack of
xen_start_info in that case.

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
2018-05-17 08:39:13 +02:00
Simon Gaiser ebf04f331f xen: xenbus_dev_frontend: Really return response string
xenbus_command_reply() did not actually copy the response string and
leaked stack content instead.

Fixes: 9a6161fe73 ("xen: return xenstore command failures via response instead of rc")
Signed-off-by: Simon Gaiser <simon@invisiblethingslab.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
2018-04-17 08:29:08 -04:00
Simon Gaiser 8fe5ab4112 xen: xenbus_dev_frontend: Verify body of XS_TRANSACTION_END
By guaranteeing that the argument of XS_TRANSACTION_END is valid we can
assume that the transaction has been closed when we get an XS_ERROR
response from xenstore (Note that we already verify that it's a valid
transaction id).

Signed-off-by: Simon Gaiser <simon@invisiblethingslab.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
2018-03-21 08:28:53 -04:00
Simon Gaiser b93008d1ac xen: xenbus: Catch closing of non existent transactions
Users of the xenbus functions should never close a non existent
transaction (for example by trying to closing the same transaction
twice) but better catch it in xs_request_exit() than to corrupt the
reference counter.

Signed-off-by: Simon Gaiser <simon@invisiblethingslab.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
2018-03-21 08:28:51 -04:00
Simon Gaiser 2a22ee6c3a xen: xenbus_dev_frontend: Fix XS_TRANSACTION_END handling
Commit fd8aa9095a ("xen: optimize xenbus driver for multiple
concurrent xenstore accesses") made a subtle change to the semantic of
xenbus_dev_request_and_reply() and xenbus_transaction_end().

Before on an error response to XS_TRANSACTION_END
xenbus_dev_request_and_reply() would not decrement the active
transaction counter. But xenbus_transaction_end() has always counted the
transaction as finished regardless of the response.

The new behavior is that xenbus_dev_request_and_reply() and
xenbus_transaction_end() will always count the transaction as finished
regardless the response code (handled in xs_request_exit()).

But xenbus_dev_frontend tries to end a transaction on closing of the
device if the XS_TRANSACTION_END failed before. Trying to close the
transaction twice corrupts the reference count. So fix this by also
considering a transaction closed if we have sent XS_TRANSACTION_END once
regardless of the return code.

Cc: <stable@vger.kernel.org> # 4.11
Fixes: fd8aa9095a ("xen: optimize xenbus driver for multiple concurrent xenstore accesses")
Signed-off-by: Simon Gaiser <simon@invisiblethingslab.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
2018-03-21 08:28:48 -04:00
Arvind Yadav 351b2bcced xen: xenbus: use put_device() instead of kfree()
Never directly free @dev after calling device_register(), even
if it returned an error! Always use put_device() to give up the
reference initialized.

Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
2018-03-08 15:30:30 +01:00
Joao Martins 29fee6eed2 xenbus: track caller request id
Commit fd8aa9095a ("xen: optimize xenbus driver for multiple concurrent
xenstore accesses") optimized xenbus concurrent accesses but in doing so
broke UABI of /dev/xen/xenbus. Through /dev/xen/xenbus applications are in
charge of xenbus message exchange with the correct header and body. Now,
after the mentioned commit the replies received by application will no
longer have the header req_id echoed back as it was on request (see
specification below for reference), because that particular field is being
overwritten by kernel.

struct xsd_sockmsg
{
  uint32_t type;  /* XS_??? */
  uint32_t req_id;/* Request identifier, echoed in daemon's response.  */
  uint32_t tx_id; /* Transaction id (0 if not related to a transaction). */
  uint32_t len;   /* Length of data following this. */

  /* Generally followed by nul-terminated string(s). */
};

Before there was only one request at a time so req_id could simply be
forwarded back and forth. To allow simultaneous requests we need a
different req_id for each message thus kernel keeps a monotonic increasing
counter for this field and is written on every request irrespective of
userspace value.

Forwarding again the req_id on userspace requests is not a solution because
we would open the possibility of userspace-generated req_id colliding with
kernel ones. So this patch instead takes another route which is to
artificially keep user req_id while keeping the xenbus logic as is. We do
that by saving the original req_id before xs_send(), use the private kernel
counter as req_id and then once reply comes and was validated, we restore
back the original req_id.

Cc: <stable@vger.kernel.org> # 4.11
Fixes: fd8aa9095a ("xen: optimize xenbus driver for multiple concurrent xenstore accesses")
Reported-by: Bhavesh Davda <bhavesh.davda@oracle.com>
Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
2018-02-17 09:40:33 +01:00
Linus Torvalds a9a08845e9 vfs: do bulk POLL* -> EPOLL* replacement
This is the mindless scripted replacement of kernel use of POLL*
variables as described by Al, done by this script:

    for V in IN OUT PRI ERR RDNORM RDBAND WRNORM WRBAND HUP RDHUP NVAL MSG; do
        L=`git grep -l -w POLL$V | grep -v '^t' | grep -v /um/ | grep -v '^sa' | grep -v '/poll.h$'|grep -v '^D'`
        for f in $L; do sed -i "-es/^\([^\"]*\)\(\<POLL$V\>\)/\\1E\\2/" $f; done
    done

with de-mangling cleanups yet to come.

NOTE! On almost all architectures, the EPOLL* constants have the same
values as the POLL* constants do.  But they keyword here is "almost".
For various bad reasons they aren't the same, and epoll() doesn't
actually work quite correctly in some cases due to this on Sparc et al.

The next patch from Al will sort out the final differences, and we
should be all done.

Scripted-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-02-11 14:34:03 -08:00
Al Viro afc9a42b74 the rest of drivers/*: annotate ->poll() instances
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2017-11-28 11:06:58 -05:00
Linus Torvalds 051089a2ee xen: features and fixes for v4.15-rc1
-----BEGIN PGP SIGNATURE-----
 Version: GnuPG v2
 
 iQEcBAABAgAGBQJaDdh4AAoJELDendYovxMvPFAH/2QjTys2ydIAdmwke4odpJ7U
 xuy7HOQCzOeZ5YsZthzCBsN90VmnDM7X7CcB8weSdjcKlXMSAWD+J1RgkL2iAJhI
 8tzIEXECrlNuz4V5mX9TmMgtPCr4qzU3fsts0pZy4fYDq1PVWDefqOwEtbpbWabb
 wRSMq/nTb9iASTMgheSC0WfhJneqtJ+J20zrzkGPCBPRFcwfppeP8/7vpkmJslBi
 eH/pfchICM4w093T/BfavnsPvhLdjgRuwVzn6+e46s4tLnZAxnLRVQ7SXZXzBORq
 /dL/qC0XH3YXdU+XfIs//giZsmLns6SxZaMr4vs6TxFtuzZBKpLtkOKo9zndvxk=
 =sZY5
 -----END PGP SIGNATURE-----

Merge tag 'for-linus-4.15-rc1-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip

Pull xen updates from Juergen Gross:
 "Xen features and fixes for v4.15-rc1

  Apart from several small fixes it contains the following features:

   - a series by Joao Martins to add vdso support of the pv clock
     interface

   - a series by Juergen Gross to add support for Xen pv guests to be
     able to run on 5 level paging hosts

   - a series by Stefano Stabellini adding the Xen pvcalls frontend
     driver using a paravirtualized socket interface"

* tag 'for-linus-4.15-rc1-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip: (34 commits)
  xen/pvcalls: fix potential endless loop in pvcalls-front.c
  xen/pvcalls: Add MODULE_LICENSE()
  MAINTAINERS: xen, kvm: track pvclock-abi.h changes
  x86/xen/time: setup vcpu 0 time info page
  x86/xen/time: set pvclock flags on xen_time_init()
  x86/pvclock: add setter for pvclock_pvti_cpu0_va
  ptp_kvm: probe for kvm guest availability
  xen/privcmd: remove unused variable pageidx
  xen: select grant interface version
  xen: update arch/x86/include/asm/xen/cpuid.h
  xen: add grant interface version dependent constants to gnttab_ops
  xen: limit grant v2 interface to the v1 functionality
  xen: re-introduce support for grant v2 interface
  xen: support priv-mapping in an HVM tools domain
  xen/pvcalls: remove redundant check for irq >= 0
  xen/pvcalls: fix unsigned less than zero error check
  xen/time: Return -ENODEV from xen_get_wallclock()
  xen/pvcalls-front: mark expected switch fall-through
  xen: xenbus_probe_frontend: mark expected switch fall-throughs
  xen/time: do not decrease steal time after live migration on xen
  ...
2017-11-16 13:06:27 -08:00
Gustavo A. R. Silva 5fa916f7ac xen: xenbus_probe_frontend: mark expected switch fall-throughs
In preparation to enabling -Wimplicit-fallthrough, mark switch cases
where we are expecting to fall through.

Addresses-Coverity-ID: 146562
Addresses-Coverity-ID: 146563
Signed-off-by: Gustavo A. R. Silva <garsilva@embeddedor.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
2017-11-03 11:36:07 -04:00
Greg Kroah-Hartman b24413180f License cleanup: add SPDX GPL-2.0 license identifier to files with no license
Many source files in the tree are missing licensing information, which
makes it harder for compliance tools to determine the correct license.

By default all files without license information are under the default
license of the kernel, which is GPL version 2.

Update the files which contain no license information with the 'GPL-2.0'
SPDX license identifier.  The SPDX identifier is a legally binding
shorthand, which can be used instead of the full boiler plate text.

This patch is based on work done by Thomas Gleixner and Kate Stewart and
Philippe Ombredanne.

How this work was done:

Patches were generated and checked against linux-4.14-rc6 for a subset of
the use cases:
 - file had no licensing information it it.
 - file was a */uapi/* one with no licensing information in it,
 - file was a */uapi/* one with existing licensing information,

Further patches will be generated in subsequent months to fix up cases
where non-standard license headers were used, and references to license
had to be inferred by heuristics based on keywords.

The analysis to determine which SPDX License Identifier to be applied to
a file was done in a spreadsheet of side by side results from of the
output of two independent scanners (ScanCode & Windriver) producing SPDX
tag:value files created by Philippe Ombredanne.  Philippe prepared the
base worksheet, and did an initial spot review of a few 1000 files.

The 4.13 kernel was the starting point of the analysis with 60,537 files
assessed.  Kate Stewart did a file by file comparison of the scanner
results in the spreadsheet to determine which SPDX license identifier(s)
to be applied to the file. She confirmed any determination that was not
immediately clear with lawyers working with the Linux Foundation.

Criteria used to select files for SPDX license identifier tagging was:
 - Files considered eligible had to be source code files.
 - Make and config files were included as candidates if they contained >5
   lines of source
 - File already had some variant of a license header in it (even if <5
   lines).

All documentation files were explicitly excluded.

The following heuristics were used to determine which SPDX license
identifiers to apply.

 - when both scanners couldn't find any license traces, file was
   considered to have no license information in it, and the top level
   COPYING file license applied.

   For non */uapi/* files that summary was:

   SPDX license identifier                            # files
   ---------------------------------------------------|-------
   GPL-2.0                                              11139

   and resulted in the first patch in this series.

   If that file was a */uapi/* path one, it was "GPL-2.0 WITH
   Linux-syscall-note" otherwise it was "GPL-2.0".  Results of that was:

   SPDX license identifier                            # files
   ---------------------------------------------------|-------
   GPL-2.0 WITH Linux-syscall-note                        930

   and resulted in the second patch in this series.

 - if a file had some form of licensing information in it, and was one
   of the */uapi/* ones, it was denoted with the Linux-syscall-note if
   any GPL family license was found in the file or had no licensing in
   it (per prior point).  Results summary:

   SPDX license identifier                            # files
   ---------------------------------------------------|------
   GPL-2.0 WITH Linux-syscall-note                       270
   GPL-2.0+ WITH Linux-syscall-note                      169
   ((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause)    21
   ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause)    17
   LGPL-2.1+ WITH Linux-syscall-note                      15
   GPL-1.0+ WITH Linux-syscall-note                       14
   ((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause)    5
   LGPL-2.0+ WITH Linux-syscall-note                       4
   LGPL-2.1 WITH Linux-syscall-note                        3
   ((GPL-2.0 WITH Linux-syscall-note) OR MIT)              3
   ((GPL-2.0 WITH Linux-syscall-note) AND MIT)             1

   and that resulted in the third patch in this series.

 - when the two scanners agreed on the detected license(s), that became
   the concluded license(s).

 - when there was disagreement between the two scanners (one detected a
   license but the other didn't, or they both detected different
   licenses) a manual inspection of the file occurred.

 - In most cases a manual inspection of the information in the file
   resulted in a clear resolution of the license that should apply (and
   which scanner probably needed to revisit its heuristics).

 - When it was not immediately clear, the license identifier was
   confirmed with lawyers working with the Linux Foundation.

 - If there was any question as to the appropriate license identifier,
   the file was flagged for further research and to be revisited later
   in time.

In total, over 70 hours of logged manual review was done on the
spreadsheet to determine the SPDX license identifiers to apply to the
source files by Kate, Philippe, Thomas and, in some cases, confirmation
by lawyers working with the Linux Foundation.

Kate also obtained a third independent scan of the 4.13 code base from
FOSSology, and compared selected files where the other two scanners
disagreed against that SPDX file, to see if there was new insights.  The
Windriver scanner is based on an older version of FOSSology in part, so
they are related.

Thomas did random spot checks in about 500 files from the spreadsheets
for the uapi headers and agreed with SPDX license identifier in the
files he inspected. For the non-uapi files Thomas did random spot checks
in about 15000 files.

In initial set of patches against 4.14-rc6, 3 files were found to have
copy/paste license identifier errors, and have been fixed to reflect the
correct identifier.

Additionally Philippe spent 10 hours this week doing a detailed manual
inspection and review of the 12,461 patched files from the initial patch
version early this week with:
 - a full scancode scan run, collecting the matched texts, detected
   license ids and scores
 - reviewing anything where there was a license detected (about 500+
   files) to ensure that the applied SPDX license was correct
 - reviewing anything where there was no detection but the patch license
   was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied
   SPDX license was correct

This produced a worksheet with 20 files needing minor correction.  This
worksheet was then exported into 3 different .csv files for the
different types of files to be modified.

These .csv files were then reviewed by Greg.  Thomas wrote a script to
parse the csv files and add the proper SPDX tag to the file, in the
format that the file expected.  This script was further refined by Greg
based on the output to detect more types of files automatically and to
distinguish between header and source .c files (which need different
comment types.)  Finally Greg ran the script using the .csv files to
generate the patches.

Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: Philippe Ombredanne <pombredanne@nexb.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2017-11-02 11:10:55 +01:00
Juergen Gross fe9c1c9555 xen: don't compile pv-specific parts if XEN_PV isn't configured
xenbus_client.c contains some functions specific for pv guests.
Enclose them with #ifdef CONFIG_XEN_PV to avoid compiling them when
they are not needed (e.g. on ARM).

Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
2017-09-18 09:13:23 -04:00
Juergen Gross 529871bb3c xen: avoid deadlock in xenbus
When starting the xenwatch thread a theoretical deadlock situation is
possible:

xs_init() contains:

    task = kthread_run(xenwatch_thread, NULL, "xenwatch");
    if (IS_ERR(task))
        return PTR_ERR(task);
    xenwatch_pid = task->pid;

And xenwatch_thread() does:

    mutex_lock(&xenwatch_mutex);
    ...
    event->handle->callback();
    ...
    mutex_unlock(&xenwatch_mutex);

The callback could call unregister_xenbus_watch() which does:

    ...
    if (current->pid != xenwatch_pid)
        mutex_lock(&xenwatch_mutex);
    ...

In case a watch is firing before xenwatch_pid could be set and the
callback of that watch unregisters a watch, then a self-deadlock would
occur.

Avoid this by setting xenwatch_pid in xenwatch_thread().

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
2017-08-11 16:45:56 +02:00
Juergen Gross 1a3fc2c402 xen: avoid deadlock in xenbus driver
There has been a report about a deadlock in the xenbus driver:

[  247.979498] ======================================================
[  247.985688] WARNING: possible circular locking dependency detected
[  247.991882] 4.12.0-rc4-00022-gc4b25c0 #575 Not tainted
[  247.997040] ------------------------------------------------------
[  248.003232] xenbus/91 is trying to acquire lock:
[  248.007875]  (&u->msgbuffer_mutex){+.+.+.}, at: [<ffff00000863e904>]
xenbus_dev_queue_reply+0x3c/0x230
[  248.017163]
[  248.017163] but task is already holding lock:
[  248.023096]  (xb_write_mutex){+.+...}, at: [<ffff00000863a940>]
xenbus_thread+0x5f0/0x798
[  248.031267]
[  248.031267] which lock already depends on the new lock.
[  248.031267]
[  248.039615]
[  248.039615] the existing dependency chain (in reverse order) is:
[  248.047176]
[  248.047176] -> #1 (xb_write_mutex){+.+...}:
[  248.052943]        __lock_acquire+0x1728/0x1778
[  248.057498]        lock_acquire+0xc4/0x288
[  248.061630]        __mutex_lock+0x84/0x868
[  248.065755]        mutex_lock_nested+0x3c/0x50
[  248.070227]        xs_send+0x164/0x1f8
[  248.074015]        xenbus_dev_request_and_reply+0x6c/0x88
[  248.079427]        xenbus_file_write+0x260/0x420
[  248.084073]        __vfs_write+0x48/0x138
[  248.088113]        vfs_write+0xa8/0x1b8
[  248.091983]        SyS_write+0x54/0xb0
[  248.095768]        el0_svc_naked+0x24/0x28
[  248.099897]
[  248.099897] -> #0 (&u->msgbuffer_mutex){+.+.+.}:
[  248.106088]        print_circular_bug+0x80/0x2e0
[  248.110730]        __lock_acquire+0x1768/0x1778
[  248.115288]        lock_acquire+0xc4/0x288
[  248.119417]        __mutex_lock+0x84/0x868
[  248.123545]        mutex_lock_nested+0x3c/0x50
[  248.128016]        xenbus_dev_queue_reply+0x3c/0x230
[  248.133005]        xenbus_thread+0x788/0x798
[  248.137306]        kthread+0x110/0x140
[  248.141087]        ret_from_fork+0x10/0x40

It is rather easy to avoid by dropping xb_write_mutex before calling
xenbus_dev_queue_reply().

Fixes: fd8aa9095a ("xen: optimize xenbus
driver for multiple concurrent xenstore accesses").

Cc: <stable@vger.kernel.org> # 4.11
Reported-by: Andre Przywara <andre.przywara@arm.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Tested-by: Andre Przywara <andre.przywara@arm.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
2017-06-25 13:11:22 +02:00
Jan Beulich ac4cde398a xenbus: remove transaction holder from list before freeing
After allocation the item is being placed on the list right away.
Consequently it needs to be taken off the list before freeing in the
case xenbus_dev_request_and_reply() failed, as in that case the
callback (xenbus_dev_queue_reply()) is not being called (and if it
was called, it should do both).

Fixes: 5584ea250a
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
2017-04-04 10:11:06 -04:00
Masanari Iida d825adb48c xenbus: Remove duplicate inclusion of linux/init.h
This patch remove duplicate inclusion of linux/init.h in
xenbus_dev_frontend.c.
Confirm successfully compile after remove the line.

Signed-off-by: Masanari Iida <standby24x7@gmail.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
2017-02-27 08:13:28 -05:00
Juergen Gross fd8aa9095a xen: optimize xenbus driver for multiple concurrent xenstore accesses
Handling of multiple concurrent Xenstore accesses through xenbus driver
either from the kernel or user land is rather lame today: xenbus is
capable to have one access active only at one point of time.

Rewrite xenbus to handle multiple requests concurrently by making use
of the request id of the Xenstore protocol. This requires to:

- Instead of blocking inside xb_read() when trying to read data from
  the xenstore ring buffer do so only in the main loop of
  xenbus_thread().

- Instead of doing writes to the xenstore ring buffer in the context of
  the caller just queue the request and do the write in the dedicated
  xenbus thread.

- Instead of just forwarding the request id specified by the caller of
  xenbus to xenstore use a xenbus internal unique request id. This will
  allow multiple outstanding requests.

- Modify the locking scheme in order to allow multiple requests being
  active in parallel.

- Instead of waiting for the reply of a user's xenstore request after
  writing the request to the xenstore ring buffer return directly to
  the caller and do the waiting in the read path.

Additionally signal handling was optimized by avoiding waking up the
xenbus thread or sending an event to Xenstore in case the addressed
entity is known to be running already.

As a result communication with Xenstore is sped up by a factor of up
to 5: depending on the request type (read or write) and the amount of
data transferred the gain was at least 20% (small reads) and went up to
a factor of 5 for large writes.

In the end some more rough edges of xenbus have been smoothed:

- Handling of memory shortage when reading from xenstore ring buffer in
  the xenbus driver was not optimal: it was busy looping and issuing a
  warning in each loop.

- In case of xenstore not running in dom0 but in a stubdom we end up
  with two xenbus threads running as the initialization of xenbus in
  dom0 expecting a local xenstored will be redone later when connecting
  to the xenstore domain. Up to now this was no problem as locking
  would prevent the two xenbus threads interfering with each other, but
  this was just a waste of kernel resources.

- An out of memory situation while writing to or reading from the
  xenstore ring buffer no longer will lead to a possible loss of
  synchronization with xenstore.

- The user read and write part are now interruptible by signals.

Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
2017-02-09 11:26:49 -05:00
Juergen Gross 5584ea250a xen: modify xenstore watch event interface
Today a Xenstore watch event is delivered via a callback function
declared as:

void (*callback)(struct xenbus_watch *,
                 const char **vec, unsigned int len);

As all watch events only ever come with two parameters (path and token)
changing the prototype to:

void (*callback)(struct xenbus_watch *,
                 const char *path, const char *token);

is the natural thing to do.

Apply this change and adapt all users.

Cc: konrad.wilk@oracle.com
Cc: roger.pau@citrix.com
Cc: wei.liu2@citrix.com
Cc: paul.durrant@citrix.com
Cc: netdev@vger.kernel.org

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Paul Durrant <paul.durrant@citrix.com>
Reviewed-by: Wei Liu <wei.liu2@citrix.com>
Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
2017-02-09 11:26:49 -05:00
Juergen Gross 332f791dc9 xen: clean up xenbus internal headers
The xenbus driver has an awful mixture of internally and globally
visible headers: some of the internally used only stuff is defined in
the global header include/xen/xenbus.h while some stuff defined in
internal headers is used by other drivers, too.

Clean this up by moving the externally used symbols to
include/xen/xenbus.h and the symbols used internally only to a new
header drivers/xen/xenbus/xenbus.h replacing xenbus_comms.h and
xenbus_probe.h

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
2017-02-09 11:26:49 -05:00
Joe Perches c0d197d55e xenbus: Neaten xenbus_va_dev_error
This function error patch can be simplified, so do so.

Remove fail: label and somewhat obfuscating, used once "error_path"
function.

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
2017-02-08 10:09:09 -05:00
Juergen Gross 61033e089c xen: remove stale xs_input_avail() from header
In drivers/xen/xenbus/xenbus_comms.h there is a stale declaration of
xs_input_avail(). Remove it.

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
2016-12-23 20:06:32 +01:00
Juergen Gross 9a6161fe73 xen: return xenstore command failures via response instead of rc
When the xenbus driver does some special handling for a Xenstore
command any error condition related to the command should be returned
via an error response instead of letting the related write operation
fail. Otherwise the user land handler might take wrong decisions
assuming the connection to Xenstore is broken.

While at it try to return the same error values xenstored would
return for those cases.

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
2016-12-23 20:06:23 +01:00
Juergen Gross 639b08810d xen: xenbus driver must not accept invalid transaction ids
When accessing Xenstore in a transaction the user is specifying a
transaction id which he normally obtained from Xenstore when starting
the transaction. Xenstore is validating a transaction id against all
known transaction ids of the connection the request came in. As all
requests of a domain not being the one where Xenstore lives share
one connection, validation of transaction ids of different users of
Xenstore in that domain should be done by the kernel of that domain
being the multiplexer between the Xenstore users in that domain and
Xenstore.

In order to prohibit one Xenstore user "hijacking" a transaction from
another user the xenbus driver has to verify a given transaction id
against all known transaction ids of the user before forwarding it to
Xenstore.

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
2016-12-23 20:06:20 +01:00
David Vrabel 581d21a2d0 xenbus: fix deadlock on writes to /proc/xen/xenbus
/proc/xen/xenbus does not work correctly.  A read blocked waiting for
a xenstore message holds the mutex needed for atomic file position
updates.  This blocks any writes on the same file handle, which can
deadlock if the write is needed to unblock the read.

Clear FMODE_ATOMIC_POS when opening this device to always get
character device like sematics.

Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
2016-12-12 15:22:13 +01:00
Pan Bian 2466d4b9d0 xen: xenbus: set error code on failure
Variable err is initialized with 0. As a result, the return value may
be 0 even if get_zeroed_page() fails to allocate memory. This patch fixes
the bug, initializing err with "-ENOMEM".

Signed-off-by: Pan Bian <bianpan2016@163.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
2016-12-08 07:53:57 +01:00
Seth Forshee f97df70b1c xenfs: Use proc_create_mount_point() to create /proc/xen
Mounting proc in user namespace containers fails if the xenbus
filesystem is mounted on /proc/xen because this directory fails
the "permanently empty" test. proc_create_mount_point() exists
specifically to create such mountpoints in proc but is currently
proc-internal. Export this interface to modules, then use it in
xenbus when creating /proc/xen.

Signed-off-by: Seth Forshee <seth.forshee@canonical.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
2016-11-17 13:52:18 +01:00
Juergen Gross 999c9af9e3 xen: make use of xenbus_read_unsigned() in xenbus
Use xenbus_read_unsigned() instead of xenbus_scanf() when possible.
This requires to change the type of the reads from int to unsigned,
but these cases have been wrong before: negative values are not allowed
for the modified cases.

Signed-off-by: Juergen Gross <jgross@suse.com>
Acked-by: David Vrabel <david.vrabel@citrix.com>
2016-11-07 13:55:36 +01:00
Juergen Gross 9c53a1792a xen: introduce xenbus_read_unsigned()
There are multiple instances of code reading an optional unsigned
parameter from Xenstore via xenbus_scanf(). Instead of repeating the
same code over and over add a service function doing the job.

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: David Vrabel <david.vrabel@citrix.com>
2016-11-07 13:55:02 +01:00
Linus Torvalds aa34e07e45 xen: fixes for 4.9-rc2
- Advertise control feature flags in xenstore.
 - Fix x86 build when XEN_PVHVM is disabled.
 -----BEGIN PGP SIGNATURE-----
 Version: GnuPG v1
 
 iQEcBAABAgAGBQJYDjVtAAoJEFxbo/MsZsTRv2UH/0YR95ajlgJnN/ldeG4KhBdV
 Oe6piyw1cbHDPvFrFFl7HgYgAiiuaMxOFk+j/XKVJ7naAOD06kWHoVzZNkpNFF4i
 2m81jGfvW3msbXd77aR+IHulWxRxQ9TE4HV2s94DiQiSJa2f02PqVCdqyJws736m
 mjDdDRzd90xb2rDI3XrcRNnjgNaFtfMLGhtwtgXI5U+Ic+uVW1VBwLefZXCI2SKw
 yUSVBwsYENgfGUJ+NmYrl53WmlSnAatrs1wClLVqm/0fD7+J2XLHRAonISTwoKtp
 z+XJthe7uWq0Fb/DMiWhvTrTn852chy9BEC6QsRBmGM6RRZG9n7x8k97NgTiqiw=
 =lM7p
 -----END PGP SIGNATURE-----

Merge tag 'for-linus-4.9-rc2-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip

Pull xen fixes from David Vrabel:

 - advertise control feature flags in xenstore

 - fix x86 build when XEN_PVHVM is disabled

* tag 'for-linus-4.9-rc2-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip:
  xenbus: check return value of xenbus_scanf()
  xenbus: prefer list_for_each()
  x86: xen: move cpu_up functions out of ifdef
  xenbus: advertise control feature flags
2016-10-24 19:52:24 -07:00
Jan Beulich c251f15c7d xenbus: check return value of xenbus_scanf()
Don't ignore errors here: Set backend state to unknown when
unsuccessful.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
2016-10-24 16:08:21 +01:00
Jan Beulich e1e5b3ff41 xenbus: prefer list_for_each()
This is more efficient than list_for_each_safe() when list modification
is accompanied by breaking out of the loop.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
2016-10-24 16:08:04 +01:00
Jan Beulich 9a035a40f7 xenbus: don't look up transaction IDs for ordinary writes
This should really only be done for XS_TRANSACTION_END messages, or
else at least some of the xenstore-* tools don't work anymore.

Fixes: 0beef634b8 ("xenbus: don't BUG() on user mode induced condition")
Reported-by: Richard Schütz <rschuetz@uni-koblenz.de>
Cc: <stable@vger.kernel.org>
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Tested-by: Richard Schütz <rschuetz@uni-koblenz.de>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
2016-08-24 18:16:18 +01:00
Linus Torvalds 08fd8c1768 xen: features and fixes for 4.8-rc0
- ACPI support for guests on ARM platforms.
 - Generic steal time support for arm and x86.
 - Support cases where kernel cpu is not Xen VCPU number (e.g., if
   in-guest kexec is used).
 - Use the system workqueue instead of a custom workqueue in various
   places.
 -----BEGIN PGP SIGNATURE-----
 Version: GnuPG v1
 
 iQEcBAABAgAGBQJXmLlrAAoJEFxbo/MsZsTRvRQH/1wOMF8BmlbZfR7H3qwDfjst
 ApNifCiZE08xDtWBlwUaBFAQxyflQS9BBiNZDVK0sysIdXeOdpWV7V0ZjRoLL+xr
 czsaaGXDcmXxJxApoMDVuT7FeP6rEk6LVAYRoHpVjJjMZGW3BbX1vZaMW4DXl2WM
 9YNaF2Lj+rpc1f8iG31nUxwkpmcXFog6ct4tu7HiyCFT3hDkHt/a4ghuBdQItCkd
 vqBa1pTpcGtQBhSmWzlylN/PV2+NKcRd+kGiwd09/O/rNzogTMCTTWeHKAtMpPYb
 Cu6oSqJtlK5o0vtr0qyLSWEGIoyjE2gE92s0wN3iCzFY1PldqdsxUO622nIj+6o=
 =G6q3
 -----END PGP SIGNATURE-----

Merge tag 'for-linus-4.8-rc0-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip

Pull xen updates from David Vrabel:
 "Features and fixes for 4.8-rc0:

   - ACPI support for guests on ARM platforms.
   - Generic steal time support for arm and x86.
   - Support cases where kernel cpu is not Xen VCPU number (e.g., if
     in-guest kexec is used).
   - Use the system workqueue instead of a custom workqueue in various
     places"

* tag 'for-linus-4.8-rc0-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip: (47 commits)
  xen: add static initialization of steal_clock op to xen_time_ops
  xen/pvhvm: run xen_vcpu_setup() for the boot CPU
  xen/evtchn: use xen_vcpu_id mapping
  xen/events: fifo: use xen_vcpu_id mapping
  xen/events: use xen_vcpu_id mapping in events_base
  x86/xen: use xen_vcpu_id mapping when pointing vcpu_info to shared_info
  x86/xen: use xen_vcpu_id mapping for HYPERVISOR_vcpu_op
  xen: introduce xen_vcpu_id mapping
  x86/acpi: store ACPI ids from MADT for future usage
  x86/xen: update cpuid.h from Xen-4.7
  xen/evtchn: add IOCTL_EVTCHN_RESTRICT
  xen-blkback: really don't leak mode property
  xen-blkback: constify instance of "struct attribute_group"
  xen-blkfront: prefer xenbus_scanf() over xenbus_gather()
  xen-blkback: prefer xenbus_scanf() over xenbus_gather()
  xen: support runqueue steal time on xen
  arm/xen: add support for vm_assist hypercall
  xen: update xen headers
  xen-pciback: drop superfluous variables
  xen-pciback: short-circuit read path used for merging write values
  ...
2016-07-27 11:35:37 -07:00
Jan Beulich e5a79475a7 xenbus: simplify xenbus_dev_request_and_reply()
No need to retain a local copy of the full request message, only the
type is really needed.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
2016-07-08 11:50:29 +01:00
Jan Beulich 7469be95a4 xenbus: don't bail early from xenbus_dev_request_and_reply()
xenbus_dev_request_and_reply() needs to track whether a transaction is
open.  For XS_TRANSACTION_START messages it calls transaction_start()
and for XS_TRANSACTION_END messages it calls transaction_end().

If sending an XS_TRANSACTION_START message fails or responds with an
an error, the transaction is not open and transaction_end() must be
called.

If sending an XS_TRANSACTION_END message fails, the transaction is
still open, but if an error response is returned the transaction is
closed.

Commit 027bd7e899 ("xen/xenbus: Avoid synchronous wait on XenBus
stalling shutdown/restart") introduced a regression where failed
XS_TRANSACTION_START messages were leaving the transaction open.  This
can cause problems with suspend (and migration) as all transactions
must be closed before suspending.

It appears that the problematic change was added accidentally, so just
remove it.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
2016-07-08 11:14:26 +01:00
Jan Beulich 0beef634b8 xenbus: don't BUG() on user mode induced condition
Inability to locate a user mode specified transaction ID should not
lead to a kernel crash. For other than XS_TRANSACTION_START also
don't issue anything to xenbus if the specified ID doesn't match that
of any active transaction.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
2016-07-07 12:19:52 +01:00
Bhaktipriya Shridhar 5ee405d9d2 xen: xenbus: Remove create_workqueue
System workqueues have been able to handle high level of concurrency
for a long time now and there's no reason to use dedicated workqueues
just to gain concurrency.  Replace dedicated xenbus_frontend_wq with the
use of system_wq.

Unlike a dedicated per-cpu workqueue created with create_workqueue(),
system_wq allows multiple work items to overlap executions even on
the same CPU; however, a per-cpu workqueue doesn't have any CPU
locality or global ordering guarantees unless the target CPU is
explicitly specified and the increase of local concurrency shouldn't
make any difference.

In this case, there is only a single work item, increase of concurrency
level by switching to system_wq should not make any difference.

Signed-off-by: Bhaktipriya Shridhar <bhaktipriya96@gmail.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
2016-07-06 10:34:49 +01:00
Linus Torvalds 55fc733c7e xen: features and fixes for 4.6-rc0
- Make earlyprintk=xen work for HVM guests.
 - Remove module support for things never built as modules.
 -----BEGIN PGP SIGNATURE-----
 Version: GnuPG v1
 
 iQEcBAABAgAGBQJW8YhlAAoJEFxbo/MsZsTRiCgH/3GnL93s/BsRTrA/DYykYqA4
 rPPkDd6WMlEbrko6FY7o4IxUAZ50LWU8wjmDNVTT+R/VKlWCVh2+ksxjbH8e0nzr
 0QohAYTdG1VGmhkrwTjKj0wC3Nr8vaDqoBXAFRz4DiQdbobn12wzXjaVrbl8RRNc
 oHDqR+DfZj6ontqx8oFkkTk7CFKIGEOtm/uBhCAV2fNkQSUCzuQyKLlarxM6jq/2
 EnLR1bhnyoy5zNFzXxmaJgZOit8QFMKvPdDRknlp9yDHYJ5zolJkv+6FPiAG6SZs
 A8yAUPQoAD+ekAiV2DIhb8qoNNNdZXdRCFBpoudwX3GyyU4O2P5Intl0xEg17Nk=
 =L8S4
 -----END PGP SIGNATURE-----

Merge tag 'for-linus-4.6-rc0-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip

Pull xen updates from David Vrabel:
 "Features and fixes for 4.6:

  - Make earlyprintk=xen work for HVM guests

  - Remove module support for things never built as modules"

* tag 'for-linus-4.6-rc0-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip:
  drivers/xen: make platform-pci.c explicitly non-modular
  drivers/xen: make sys-hypervisor.c explicitly non-modular
  drivers/xen: make xenbus_dev_[front/back]end explicitly non-modular
  drivers/xen: make [xen-]ballon explicitly non-modular
  xen: audit usages of module.h ; remove unnecessary instances
  xen/x86: Drop mode-selecting ifdefs in startup_xen()
  xen/x86: Zero out .bss for PV guests
  hvc_xen: make early_printk work with HVM guests
  hvc_xen: fix xenboot for DomUs
  hvc_xen: add earlycon support
2016-03-22 12:55:17 -07:00
Paul Gortmaker ab1241a1fc drivers/xen: make xenbus_dev_[front/back]end explicitly non-modular
The Makefile / Kconfig currently controlling compilation here is:

obj-y   += xenbus_dev_frontend.o
[...]
obj-$(CONFIG_XEN_BACKEND) += xenbus_dev_backend.o

...with:

drivers/xen/Kconfig:config XEN_BACKEND
drivers/xen/Kconfig:    bool "Backend driver support"

...meaning that they currently are not being built as modules by anyone.

Lets remove the modular code that is essentially orphaned, so that
when reading the driver there is no doubt it is builtin-only.

Since module_init translates to device_initcall in the non-modular
case, the init ordering remains unchanged with this commit.

We also delete the MODULE_LICENSE tag since all that information
is already contained at the top of the file in the comments.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Reviewed-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
2016-03-21 15:13:55 +00:00
Paul Gortmaker 59aa56bf2a xen: audit usages of module.h ; remove unnecessary instances
Code that uses no modular facilities whatsoever should not be
sourcing module.h at all, since that header drags in a bunch
of other headers with it.

Similarly, code that is not explicitly using modular facilities
like module_init() but only is declaring module_param setup
variables should be using moduleparam.h and not the larger
module.h file for that.

In making this change, we also uncover an implicit use of BUG()
in inline fcns within arch/arm/include/asm/xen/hypercall.h so
we explicitly source <linux/bug.h> for that file now.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Reviewed-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
2016-03-21 15:13:32 +00:00
Linus Torvalds 692b8c663c Xen bug fixes for 4.5-rc5
- Two scsiback fixes (resource leak and spurious warning).
 - Fix DMA mapping of compound pages on arm/arm64.
 - Fix some pciback regressions in MSI-X handling.
 - Fix a pcifront crash due to some uninitialize state.
 -----BEGIN PGP SIGNATURE-----
 Version: GnuPG v1
 
 iQEcBAABAgAGBQJWyvatAAoJEFxbo/MsZsTRBFcH+wWnv0/N+gKib3cKCI4lwmTg
 n8iVgf8dNWwD36M2s/OlzCAglAIt8Xr6ySNvPqTerpm7lT9yXlIVQxGXTbIGuTAA
 h8Kt8WiC0BNLHHlLxBuCz62KR47DvMhsr84lFURE8FmpUiulFjXmRcbrZkHIMYRS
 l/X+xJWO1vxwrSYho0P9n3ksTWHm488DTPvZz3ICNI2G2sndDfbT3gv3tMDaQhcX
 ZaQR93vtIoldqk29Ga59vaVtksbgxHZIbasY9PQ8rqOxHJpDQbPzpjocoLxAzf50
 cioQVyKQ7i9vUvZ+B3TTAOhxisA2hDwNhLGQzmjgxe2TXeKdo3yjYwO6m1dDBzY=
 =VY/S
 -----END PGP SIGNATURE-----

Merge tag 'for-linus-4.5-rc5-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip

Pull xen bug fixes from David Vrabel:

 - Two scsiback fixes (resource leak and spurious warning).

 - Fix DMA mapping of compound pages on arm/arm64.

 - Fix some pciback regressions in MSI-X handling.

 - Fix a pcifront crash due to some uninitialize state.

* tag 'for-linus-4.5-rc5-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip:
  xen/pcifront: Fix mysterious crashes when NUMA locality information was extracted.
  xen/pcifront: Report the errors better.
  xen/pciback: Save the number of MSI-X entries to be copied later.
  xen/pciback: Check PF instead of VF for PCI_COMMAND_MEMORY
  xen: fix potential integer overflow in queue_reply
  xen/arm: correctly handle DMA mapping of compound pages
  xen/scsiback: avoid warnings when adding multiple LUNs to a domain
  xen/scsiback: correct frontend counting
2016-02-22 13:57:01 -08:00
Insu Yun 85c0a87cd1 xen: fix potential integer overflow in queue_reply
When len is greater than UINT_MAX - sizeof(*rb), in next allocation,
it can overflow integer range and allocates small size of heap.
After that, memcpy will overflow the allocated heap.
Therefore, it needs to check the size of given length.

Signed-off-by: Insu Yun <wuninsu@gmail.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
2016-02-15 13:56:57 +00:00
Michael S. Tsirkin 5bb0c9be2a xenbus: use virt_xxx barriers
drivers/xen/xenbus/xenbus_comms.c uses
full memory barriers to communicate with the other side.

For guests compiled with CONFIG_SMP, smp_wmb and smp_mb
would be sufficient, so mb() and wmb() here are only needed if
a non-SMP guest runs on an SMP host.

Switch to virt_xxx barriers which serve this exact purpose.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: David Vrabel <david.vrabel@citrix.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
2016-01-12 20:47:03 +02:00
Julien Grall 89bf4b4e4a xenbus: Support multiple grants ring with 64KB
The PV ring may use multiple grants and expect them to be mapped
contiguously in the virtual memory.

Although, the current code is relying on a Linux page will be mapped to
a single grant. On build where Linux is using a different page size than
the grant (i.e other than 4KB), the grant will always be mapped on the
first 4KB of each Linux page which make the final ring not contiguous in
the memory.

This can be fixed by mapping multiple grant in a same Linux page.

Signed-off-by: Julien Grall <julien.grall@citrix.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
2015-10-23 14:20:47 +01:00
Julien Grall 9cce2914e2 xen/xenbus: Rename *RING_PAGE* to *RING_GRANT*
Linux may use a different page size than the size of grant. So make
clear that the order is actually in number of grant.

Signed-off-by: Julien Grall <julien.grall@citrix.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
2015-10-23 14:20:46 +01:00
Julien Grall 7d567928db xen/xenbus: Use Xen page definition
All the ring (xenstore, and PV rings) are always based on the page
granularity of Xen.

Signed-off-by: Julien Grall <julien.grall@citrix.com>
Reviewed-by: David Vrabel <david.vrabel@citrix.com>
Reviewed-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
2015-10-23 14:20:37 +01:00
David Vrabel 81b286e0f1 xen/balloon: make alloc_xenballoon_pages() always allocate low pages
All users of alloc_xenballoon_pages() wanted low memory pages, so
remove the option for high memory.

Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
2015-10-23 14:20:05 +01:00