Make host_signal_handler slightly easier to read.
Acked-by: Helge Deller <deller@gmx.de>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Install the host signal handler at the same time we are
probing the target signals for SIG_IGN/SIG_DFL. Ignore
unmapped target signals.
Acked-by: Helge Deller <deller@gmx.de>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Do not return a valid signal number in one domain
when given an invalid signal number in the other domain.
Acked-by: Helge Deller <deller@gmx.de>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
The set of fatal signals is really immaterial. If one arrives,
and is unhandled, then the qemu process dies and the parent gets
the correct signal.
It is only for those signals which we would like to perform a
guest core dump instead of a host core dump that we need to catch.
Acked-by: Helge Deller <deller@gmx.de>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
If there is an internal program error in the qemu source code which
raises SIGSEGV or SIGBUS, we currently assume the signal belongs to
the guest. With an artificial error introduced, we will now print
QEMU internal SIGSEGV {code=MAPERR, addr=(nil)}
Signed-off-by: Helge Deller <deller@gmx.de>
Message-Id: <20230812164314.352131-1-deller@gmx.de>
[rth: Use in_code_gen_buffer and die_with_signal; drop backtrace]
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
This line is supposed to be unreachable, but if we're going to
have it at all, SIGABRT via abort() is subject to the same signal
peril that created this function in the first place.
We can _exit immediately without peril.
Acked-by: Helge Deller <deller@gmx.de>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Because we trap so many signals for use by the guest,
we have to take extra steps to exit properly.
Acked-by: Helge Deller <deller@gmx.de>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Do not assert success, but return any failure received.
Additionally, fix the method of earlier error return in target_munmap.
Reported-by: Andreas Schwab <schwab@suse.de>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Since support for LSX and LASX is landed in QEMU recently, we can update
HWCAPS accordingly.
Signed-off-by: Jiajie Chen <c@jia.je>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20231001085315.1692667-1-c@jia.je>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
sh4 uses gUSA (general UserSpace Atomicity) to provide atomicity on CPUs
that don't have atomic instructions. A gUSA region that adds 1 to an
atomic variable stored in @R2 looks like this:
4004b6: 03 c7 mova 4004c4 <gusa+0x10>,r0
4004b8: f3 61 mov r15,r1
4004ba: 09 00 nop
4004bc: fa ef mov #-6,r15
4004be: 22 63 mov.l @r2,r3
4004c0: 01 73 add #1,r3
4004c2: 32 22 mov.l r3,@r2
4004c4: 13 6f mov r1,r15
R0 contains a pointer to the end of the gUSA region
R1 contains the saved stack pointer
R15 contains negative length of the gUSA region
When this region is interrupted by a signal, the kernel detects if
R15 >= -128U. If yes, the kernel rolls back PC to the beginning of the
region and restores SP by copying R1 to R15.
The problem happens if we are interrupted by a signal at address 4004c4.
R15 still holds the value -6, but the atomic value was already written by
an instruction at address 4004c2. In this situation we can't undo the
gUSA. The function unwind_gusa does nothing, the signal handler attempts
to push a signal frame to the address -6 and crashes.
This patch fixes it, so that if we are interrupted at the last instruction
in a gUSA region, we copy R1 to R15 to restore the correct stack pointer
and avoid crashing.
There's another bug: if we are interrupted in a delay slot, we save the
address of the instruction in the delay slot. We must save the address of
the previous instruction.
Cc: qemu-stable@nongnu.org
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Reviewed-by: Yoshinori Sato <ysato@users.sourcefoege.jp>
Message-Id: <b16389f7-6c62-70b7-59b3-87533c0bcc@redhat.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
QEMU mips userspace emulation crashes with "qemu: unhandled CPU exception
0x15 - aborting" when one of the integer arithmetic instructions detects
an overflow.
This patch fixes it so that it delivers SIGFPE with FPE_INTOVF instead.
Cc: qemu-stable@nongnu.org
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Message-Id: <3ef979a8-3ee1-eb2d-71f7-d788ff88dd11@redhat.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
The previous change, 2d385be615, assumed !PAGE_VALID meant that
the page would be unmapped by the elf image. However, since we
reserved the entire image space via mmap, PAGE_VALID will always
be set. Instead, assume PROT_NONE for the same condition.
Furthermore, assume bss is only ever present for writable segments,
and that there is no page overlap between PT_LOAD segments.
Instead of an assert, return false to indicate failure.
Cc: qemu-stable@nongnu.org
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1854
Fixes: 2d385be615 ("linux-user: Do not adjust zero_bss for host page size")
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
The function is currently called from two sites, one always gives it a
NULL Error and the other always gives it a non-NULL Error.
In the non-NULL case, all it does it trace the error and return. One
of the callers already have tracing, add a tracepoint to the other and
stop passing the error into the function.
Cc: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
Message-ID: <20231012134343.23757-4-farosas@suse.de>
The preferred usage of the Error type is to always set both the return
code and the error when a failure happens. As all code called from the
send thread follows this pattern, we'll always have the return code
and the error set at the same time.
Aside from the convention, in this piece of code this must be the
case, otherwise the if (ret != 0) would be exiting the thread without
calling multifd_send_terminate_threads() which is incorrect.
Unify both paths to make it clear that both are taken when there's an
error.
Signed-off-by: Fabiano Rosas <farosas@suse.de>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
Message-ID: <20231012134343.23757-3-farosas@suse.de>
We're about to enable support for other transports in multifd, so
remove direct references to sockets.
Signed-off-by: Fabiano Rosas <farosas@suse.de>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
Message-ID: <20231012134343.23757-2-farosas@suse.de>
We don't need to do this in two pieces. One single function makes it
easier to grasp, specially since it removes the indirection on the
return value handling.
Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
Message-ID: <20231011184604.32364-7-farosas@suse.de>
It makes a bit more sense to have the zero page handling of xbzrle
right where we save the zero page.
Also invert the exit condition to remove one level of indentation
which makes the next patch easier to grasp.
Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
Message-ID: <20231011184604.32364-6-farosas@suse.de>
We don't need the QEMUFile when we're already passing the
PageSearchStatus.
Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
Message-ID: <20231011184604.32364-5-farosas@suse.de>
'rs' is not used in that function. It's a leftover from commit
9360447d34 ("ram: Use MigrationStats for statistics").
Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
Message-ID: <20231011184604.32364-4-farosas@suse.de>
Extract the ramblock parsing code into a routine that operates on the
sequence of headers from the stream and another the parses the
individual ramblock. This makes ram_load_precopy() easier to
comprehend.
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>
Signed-off-by: Juan Quintela <quintela@redhat.com>
Message-ID: <20231011184604.32364-3-farosas@suse.de>
Sometimes multifd sends just sync packet with no pages
(normal_num is 0). In this case the old value is being
preserved and being accounted for while only packet_len
is being transferred.
Reset it to 0 after sending and accounting for.
Signed-off-by: Elena Ufimtseva <elena.ufimtseva@oracle.com>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
Message-ID: <20231011184358.97349-5-elena.ufimtseva@oracle.com>
Previous commit cbec7eb768
"migration/multifd: Compute transferred bytes correctly"
removed accounting for packet_len in non-rdma
case, but the next_packet_size only accounts for pages, not for
the header packet (normal_pages * PAGE_SIZE) that is being sent
as iov[0]. The packet_len part should be added to account for
the size of MultiFDPacket and the array of the offsets.
Signed-off-by: Elena Ufimtseva <elena.ufimtseva@oracle.com>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
Message-ID: <20231011184358.97349-4-elena.ufimtseva@oracle.com>
In migration rate limiting atomic operations are used
to read the rate limit variables and transferred bytes and
they are expensive. Check first if rate_limit_max is equal
to RATE_LIMIT_DISABLED and return false immediately if so.
Note that with this patch we will also will stop flushing
by not calling qemu_fflush() from migration_transferred_bytes()
if the migration rate is not exceeded.
This should be fine since migration thread calls in the loop
migration_update_counters from migration_rate_limit() that
calls the migration_transferred_bytes() and flushes there.
Signed-off-by: Elena Ufimtseva <elena.ufimtseva@oracle.com>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Reviewed-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
Message-ID: <20231011184358.97349-2-elena.ufimtseva@oracle.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
Message-ID: <20231013104736.31722-2-quintela@redhat.com>
Change code that is:
int ret;
...
ret = foo();
if (ret[ < 0]?) {
to:
if (foo()[ < 0]) {
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Reviewed-by: Li Zhijian <lizhijian@fujitsu.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
Message-ID: <20231011203527.9061-14-quintela@redhat.com>
Declare all variables that are only used inside a for loop inside the
for statement.
This makes clear that they are not used outside of the for loop.
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Reviewed-by: Li Zhijian <lizhijian@fujitsu.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
Message-ID: <20231011203527.9061-13-quintela@redhat.com>
Once there, all the uses are local to the for, so declare the variable
inside the for statement.
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Reviewed-by: Li Zhijian <lizhijian@fujitsu.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
Message-ID: <20231011203527.9061-12-quintela@redhat.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Li Zhijian <lizhijian@fujitsu.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
Message-ID: <20231011203527.9061-11-quintela@redhat.com>
Functions are long enough even without this.
Reviewed-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Li Zhijian <lizhijian@fujitsu.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
Message-ID: <20231011203527.9061-10-quintela@redhat.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Li Zhijian <lizhijian@fujitsu.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
Message-ID: <20231011203527.9061-9-quintela@redhat.com>
The only user was rdma, and its use is gone.
Reviewed-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Li Zhijian <lizhijian@fujitsu.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
Message-ID: <20231011203527.9061-8-quintela@redhat.com>
The only user of ram_control_save_page() and save_page() hook was
rdma. Just move the function to rdma.c, rename it to
rdma_control_save_page().
Reviewed-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Li Zhijian <lizhijian@fujitsu.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
Message-ID: <20231011203527.9061-7-quintela@redhat.com>
There is only one flag called with: RAM_CONTROL_BLOCK_REG.
Reviewed-by: Li Zhijian <lizhijian@fujitsu.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
Message-ID: <20231011203527.9061-6-quintela@redhat.com>
Instead of going through ram_control_load_hook(), call
qemu_rdma_registration_handle() directly.
Reviewed-by: Li Zhijian <lizhijian@fujitsu.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
Message-ID: <20231011203527.9061-5-quintela@redhat.com>
Once there:
- Remove unused data parameter
- unfold it in its callers
- change all callers to call qemu_rdma_registration_stop()
- We need to call QIO_CHANNEL_RDMA() after we check for migrate_rdma()
Reviewed-by: Li Zhijian <lizhijian@fujitsu.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
Message-ID: <20231011203527.9061-4-quintela@redhat.com>
Once there:
- Remove unused data parameter
- unfold it in its callers.
- change all callers to call qemu_rdma_registration_start()
- We need to call QIO_CHANNEL_RDMA() after we check for migrate_rdma()
Reviewed-by: Li Zhijian <lizhijian@fujitsu.com>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Signed-off-by: Juan Quintela <quintela@redhat.com>
Message-ID: <20231011203527.9061-3-quintela@redhat.com>
Helper to say if we are doing a migration over rdma.
Reviewed-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Li Zhijian <lizhijian@fujitsu.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
Message-ID: <20231011203527.9061-2-quintela@redhat.com>
RDMA was having trouble because
migrate_multifd_flush_after_each_section() can only be true or false,
but we don't want to send any flush when we are not in multifd
migration.
CC: Fabiano Rosas <farosas@suse.de
Fixes: 294e5a4034 ("multifd: Only flush once each full round of memory")
Reported-by: Li Zhijian <lizhijian@fujitsu.com>
Reviewed-by: Li Zhijian <lizhijian@fujitsu.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
Message-ID: <20231011205548.10571-2-quintela@redhat.com>
This is intended to be a semantic revert of commit 9b09503752
("migration: run setup callbacks out of big lock"). There have been so
many changes since that commit (e.g. a new setup callback
dirty_bitmap_save_setup() that also needs to be adapted now), it's
easier to do the revert manually.
For snapshots, the bdrv_writev_vmstate() function is used during setup
(in QIOChannelBlock backing the QEMUFile), but not holding the BQL
while calling it could lead to an assertion failure. To understand
how, first note the following:
1. Generated coroutine wrappers for block layer functions spawn the
coroutine and use AIO_WAIT_WHILE()/aio_poll() to wait for it.
2. If the host OS switches threads at an inconvenient time, it can
happen that a bottom half scheduled for the main thread's AioContext
is executed as part of a vCPU thread's aio_poll().
An example leading to the assertion failure is as follows:
main thread:
1. A snapshot-save QMP command gets issued.
2. snapshot_save_job_bh() is scheduled.
vCPU thread:
3. aio_poll() for the main thread's AioContext is called (e.g. when
the guest writes to a pflash device, as part of blk_pwrite which is a
generated coroutine wrapper).
4. snapshot_save_job_bh() is executed as part of aio_poll().
3. qemu_savevm_state() is called.
4. qemu_mutex_unlock_iothread() is called. Now
qemu_get_current_aio_context() returns 0x0.
5. bdrv_writev_vmstate() is executed during the usual savevm setup
via qemu_fflush(). But this function is a generated coroutine wrapper,
so it uses AIO_WAIT_WHILE. There, the assertion
assert(qemu_get_current_aio_context() == qemu_get_aio_context());
will fail.
To fix it, ensure that the BQL is held during setup. While it would
only be needed for snapshots, adapting migration too avoids additional
logic for conditional locking/unlocking in the setup callbacks.
Writing the header could (in theory) also trigger qemu_fflush() and
thus bdrv_writev_vmstate(), so the locked section also covers the
qemu_savevm_state_header() call, even for migration for consistency.
The section around multifd_send_sync_main() needs to be unlocked to
avoid a deadlock. In particular, the multifd_save_setup() function calls
socket_send_channel_create() using multifd_new_send_channel_async() as a
callback and then waits for the callback to signal via the
channels_ready semaphore. The connection happens via
qio_task_run_in_thread(), but the callback is only executed via
qio_task_thread_result() which is scheduled for the main event loop.
Without unlocking the section, the main thread would never get to
process the task result and the callback meaning there would be no
signal via the channels_ready semaphore.
The comment in ram_init_bitmaps() was introduced by 4987783400
("migration: fix incorrect memory_global_dirty_log_start outside BQL")
and is removed, because it referred to the qemu_mutex_lock_iothread()
call.
Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
Message-ID: <20231013105839.415989-1-f.ebner@proxmox.com>
Add basic tests for file-based migration.
Note that we cannot use test_precopy_common because that routine
expects it to be possible to run the migration live. With the file
transport there is no live migration because we must wait for the
source to finish writing the migration data to the file before the
destination can start reading. Add a new migration function
specifically to handle the file migration.
Reviewed-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>
Signed-off-by: Juan Quintela <quintela@redhat.com>
Message-ID: <20230712190742.22294-7-farosas@suse.de>
Add a smoke test that migrates to a file and gives it to the
script. It should catch the most annoying errors such as changes in
the ram flags.
After code has been merged it becomes way harder to figure out what is
causing the script to fail, the person making the change is the most
likely to know right away what the problem is.
Signed-off-by: Fabiano Rosas <farosas@suse.de>
Acked-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
Message-ID: <20231009184326.15777-7-farosas@suse.de>
The migration code uses unsigned values for 16, 32 and 64-bit
operations. Fix the script to do the same.
This was causing an issue when parsing the migration stream generated
on the ppc64 target because one of instance_ids was larger than the
32bit signed maximum:
Traceback (most recent call last):
File "/home/fabiano/kvm/qemu/build/scripts/analyze-migration.py", line 658, in <module>
dump.read(dump_memory = args.memory)
File "/home/fabiano/kvm/qemu/build/scripts/analyze-migration.py", line 592, in read
classdesc = self.section_classes[section_key]
KeyError: ('spapr_iommu', -2147483648)
Signed-off-by: Fabiano Rosas <farosas@suse.de>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
Message-ID: <20231009184326.15777-6-farosas@suse.de>
The script is currently broken when the x-ignore-shared capability is
used:
Traceback (most recent call last):
File "./scripts/analyze-migration.py", line 656, in <module>
dump.read(dump_memory = args.memory)
File "./scripts/analyze-migration.py", line 593, in read
section.read()
File "./scripts/analyze-migration.py", line 163, in read
self.name = self.file.readstr(len = namelen)
File "./scripts/analyze-migration.py", line 53, in readstr
return self.readvar(len).decode('utf-8')
UnicodeDecodeError: 'utf-8' codec can't decode byte 0x82 in position 55: invalid start byte
We're currently adding data to the middle of the ram section depending
on the presence of the capability. As a consequence, any code loading
the ram section needs to know about capabilities so it can interpret
the stream.
Skip the byte that's added when x-ignore-shared is used to fix the
script.
Signed-off-by: Fabiano Rosas <farosas@suse.de>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
Message-ID: <20231009184326.15777-5-farosas@suse.de>
The script is broken when the configuration/capabilities section is
present. Add support for parsing the capabilities so we can fix it in
the next patch.
Signed-off-by: Fabiano Rosas <farosas@suse.de>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
Message-ID: <20231009184326.15777-4-farosas@suse.de>
The 'configuration' state subsections are currently not being parsed
and the script fails when analyzing an aarch64 stream:
Traceback (most recent call last):
File "./scripts/analyze-migration.py", line 625, in <module>
dump.read(dump_memory = args.memory)
File "./scripts/analyze-migration.py", line 571, in read
raise Exception("Unknown section type: %d" % section_type)
Exception: Unknown section type: 5
Signed-off-by: Fabiano Rosas <farosas@suse.de>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
Message-ID: <20231009184326.15777-3-farosas@suse.de>
Make the migration json writer part of MigrationState struct, allowing
the 'configuration' object be serialized to json.
This will facilitate the parsing of the 'configuration' object in the
next patch that fixes analyze-migration.py for arm.
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
Message-ID: <20231009184326.15777-2-farosas@suse.de>
qemu_ram_block_from_host() may return NULL, which will be dereferenced w/o
check. Usualy return value is checked for this function.
Found by Linux Verification Center (linuxtesting.org) with SVACE.
Signed-off-by: Dmitry Frolov <frolov@swemel.ru>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Reviewed-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
Message-ID: <20231010104851.802947-1-frolov@swemel.ru>
Migration bandwidth is a very important value to live migration. It's
because it's one of the major factors that we'll make decision on when to
switchover to destination in a precopy process.
This value is currently estimated by QEMU during the whole live migration
process by monitoring how fast we were sending the data. This can be the
most accurate bandwidth if in the ideal world, where we're always feeding
unlimited data to the migration channel, and then it'll be limited to the
bandwidth that is available.
However in reality it may be very different, e.g., over a 10Gbps network we
can see query-migrate showing migration bandwidth of only a few tens of
MB/s just because there are plenty of other things the migration thread
might be doing. For example, the migration thread can be busy scanning
zero pages, or it can be fetching dirty bitmap from other external dirty
sources (like vhost or KVM). It means we may not be pushing data as much
as possible to migration channel, so the bandwidth estimated from "how many
data we sent in the channel" can be dramatically inaccurate sometimes.
With that, the decision to switchover will be affected, by assuming that we
may not be able to switchover at all with such a low bandwidth, but in
reality we can.
The migration may not even converge at all with the downtime specified,
with that wrong estimation of bandwidth, keeping iterations forever with a
low estimation of bandwidth.
The issue is QEMU itself may not be able to avoid those uncertainties on
measuing the real "available migration bandwidth". At least not something
I can think of so far.
One way to fix this is when the user is fully aware of the available
bandwidth, then we can allow the user to help providing an accurate value.
For example, if the user has a dedicated channel of 10Gbps for migration
for this specific VM, the user can specify this bandwidth so QEMU can
always do the calculation based on this fact, trusting the user as long as
specified. It may not be the exact bandwidth when switching over (in which
case qemu will push migration data as fast as possible), but much better
than QEMU trying to wildly guess, especially when very wrong.
A new parameter "avail-switchover-bandwidth" is introduced just for this.
So when the user specified this parameter, instead of trusting the
estimated value from QEMU itself (based on the QEMUFile send speed), it
trusts the user more by using this value to decide when to switchover,
assuming that we'll have such bandwidth available then.
Note that specifying this value will not throttle the bandwidth for
switchover yet, so QEMU will always use the full bandwidth possible for
sending switchover data, assuming that should always be the most important
way to use the network at that time.
This can resolve issues like "unconvergence migration" which is caused by
hilarious low "migration bandwidth" detected for whatever reason.
Reported-by: Zhiyi Guo <zhguo@redhat.com>
Reviewed-by: Joao Martins <joao.m.martins@oracle.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
Message-ID: <20231010221922.40638-1-peterx@redhat.com>
