A kernel bug was introduced in v4.15 via commit 71a7d3d78e3c which
adds a test for address space wrap-around in the vfio DMA unmap path.
Unfortunately due to overflow, the kernel detects an unmap of the last
page in the 64-bit address space as a wrap-around. In QEMU, a Q35
guest with VT-d emulation and guest IOMMU enabled will attempt to make
such an unmap request during VM system reset, triggering an error:
qemu-kvm: VFIO_UNMAP_DMA: -22
qemu-kvm: vfio_dma_unmap(0x561f059948f0, 0xfef00000, 0xffffffff01100000) = -22 (Invalid argument)
Here the IOVA start address (0xfef00000) and the size parameter
(0xffffffff01100000) add to exactly 2^64, triggering the bug. A
kernel fix is queued for the Linux v5.0 release to address this.
This patch implements a workaround to retry the unmap, excluding the
final page of the range when we detect an unmap failing which matches
the requirements for this issue. This is expected to be a safe and
complete workaround as the VT-d address space does not extend to the
full 64-bit space and therefore the last page should never be mapped.
This workaround can be removed once all kernels with this bug are
sufficiently deprecated.
Link: https://bugzilla.redhat.com/show_bug.cgi?id=1662291
Reported-by: Pei Zhang <pezhang@redhat.com>
Debugged-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
The '%m' format instructs glibc's printf()/syslog() implementation to
insert the contents of strerror(errno). Since this is a glibc extension
it should generally be avoided in QEMU due to need for portability to a
variety of platforms.
Even though vfio is Linux-only code that could otherwise use "%m", it
must still be avoided in trace-events files because several of the
backends do not use the format string and so this error information is
invisible to them.
The errno string value should be given as an explicit trace argument
instead, making it accessible to all backends. This also allows it to
work correctly with future patches that use the format string with
systemtap's simple printf code.
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Message-id: 20190123120016.4538-4-berrange@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
If a vfio assigned device makes use of a physical IOMMU, then memory
ballooning is necessarily inhibited due to the page pinning, lack of
page level granularity at the IOMMU, and sufficient notifiers to both
remove the page on balloon inflation and add it back on deflation.
However, not all devices are backed by a physical IOMMU. In the case
of mediated devices, if a vendor driver is well synchronized with the
guest driver, such that only pages actively used by the guest driver
are pinned by the host mdev vendor driver, then there should be no
overlap between pages available for the balloon driver and pages
actively in use by the device. Under these conditions, ballooning
should be safe.
vfio-ccw devices are always mediated devices and always operate under
the constraints above. Therefore we can consider all vfio-ccw devices
as balloon compatible.
The situation is far from straightforward with vfio-pci. These
devices can be physical devices with physical IOMMU backing or
mediated devices where it is unknown whether a physical IOMMU is in
use or whether the vendor driver is well synchronized to the working
set of the guest driver. The safest approach is therefore to assume
all vfio-pci devices are incompatible with ballooning, but allow user
opt-in should they have further insight into mediated devices.
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
With vfio ioeventfd support, we can program vfio-pci to perform a
specified BAR write when an eventfd is triggered. This allows the
KVM ioeventfd to be wired directly to vfio-pci, entirely avoiding
userspace handling for these events. On the same micro-benchmark
where the ioeventfd got us to almost 90% of performance versus
disabling the GeForce quirks, this gets us to within 95%.
Reviewed-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
The NVIDIA BAR0 quirks virtualize the PCI config space mirrors found
in device MMIO space. Normally PCI config space is considered a slow
path and further optimization is unnecessary, however NVIDIA uses a
register here to enable the MSI interrupt to re-trigger. Exiting to
QEMU for this MSI-ACK handling can therefore rate limit our interrupt
handling. Fortunately the MSI-ACK write is easily detected since the
quirk MemoryRegion otherwise has very few accesses, so simply looking
for consecutive writes with the same data is sufficient, in this case
10 consecutive writes with the same data and size is arbitrarily
chosen. We configure the KVM ioeventfd with data match, so there's
no risk of triggering for the wrong data or size, but we do risk that
pathological driver behavior might consume all of QEMU's file
descriptors, so we cap ourselves to 10 ioeventfds for this purpose.
In support of the above, generic ioeventfd infrastructure is added
for vfio quirks. This automatically initializes an ioeventfd list
per quirk, disables and frees ioeventfds on exit, and allows
ioeventfds marked as dynamic to be dropped on device reset. The
rationale for this latter feature is that useful ioeventfds may
depend on specific driver behavior and since we necessarily place a
cap on our use of ioeventfds, a machine reset is a reasonable point
at which to assume a new driver and re-profile.
Reviewed-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Commit 567b5b309a ("vfio/pci: Relax DMA map errors for MMIO regions")
added an error message if a passed memory section address or size
is not aligned to the page size and thus cannot be DMA mapped.
This patch fixes the trace by printing the region name and the
memory region section offset within the address space (instead of
offset_within_region).
We also turn the error_report into a trace event. Indeed, In some
cases, the traces can be confusing to non expert end-users and
let think the use case does not work (whereas it works as before).
This is the case where a BAR is successively mapped at different
GPAs and its sections are not compatible with dma map. The listener
is called several times and traces are issued for each intermediate
mapping. The end-user cannot easily match those GPAs against the
final GPA output by lscpi. So let's keep those information to
informed users. In mid term, the plan is to advise the user about
BAR relocation relevance.
Fixes: 567b5b309a ("vfio/pci: Relax DMA map errors for MMIO regions")
Signed-off-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Recently proposed vfio-pci kernel changes (v4.16) remove the
restriction preventing userspace from mmap'ing PCI BARs in areas
overlapping the MSI-X vector table. This change is primarily intended
to benefit host platforms which make use of system page sizes larger
than the PCI spec recommendation for alignment of MSI-X data
structures (ie. not x86_64). In the case of POWER systems, the SPAPR
spec requires the VM to program MSI-X using hypercalls, rendering the
MSI-X vector table unused in the VM view of the device. However,
ARM64 platforms also support 64KB pages and rely on QEMU emulation of
MSI-X. Regardless of the kernel driver allowing mmaps overlapping
the MSI-X vector table, emulation of the MSI-X vector table also
prevents direct mapping of device MMIO spaces overlapping this page.
Thanks to the fact that PCI devices have a standard self discovery
mechanism, we can try to resolve this by relocating the MSI-X data
structures, either by creating a new PCI BAR or extending an existing
BAR and updating the MSI-X capability for the new location. There's
even a very slim chance that this could benefit devices which do not
adhere to the PCI spec alignment guidelines on x86_64 systems.
This new x-msix-relocation option accepts the following choices:
off: Disable MSI-X relocation, use native device config (default)
auto: Use a known good combination for the platform/device (none yet)
bar0..bar5: Specify the target BAR for MSI-X data structures
If compatible, the target BAR will either be created or extended and
the new portion will be used for MSI-X emulation.
The first obvious user question with this option is how to determine
whether a given platform and device might benefit from this option.
In most cases, the answer is that it won't, especially on x86_64.
Devices often dedicate an entire BAR to MSI-X and therefore no
performance sensitive registers overlap the MSI-X area. Take for
example:
# lspci -vvvs 0a:00.0
0a:00.0 Ethernet controller: Intel Corporation I350 Gigabit Network Connection
...
Region 0: Memory at db680000 (32-bit, non-prefetchable) [size=512K]
Region 3: Memory at db7f8000 (32-bit, non-prefetchable) [size=16K]
...
Capabilities: [70] MSI-X: Enable+ Count=10 Masked-
Vector table: BAR=3 offset=00000000
PBA: BAR=3 offset=00002000
This device uses the 16K bar3 for MSI-X with the vector table at
offset zero and the pending bits arrary at offset 8K, fully honoring
the PCI spec alignment guidance. The data sheet specifically refers
to this as an MSI-X BAR. This device would not see a benefit from
MSI-X relocation regardless of the platform, regardless of the page
size.
However, here's another example:
# lspci -vvvs 02:00.0
02:00.0 Serial Attached SCSI controller: xxxxxxxx
...
Region 0: I/O ports at c000 [size=256]
Region 1: Memory at ef640000 (64-bit, non-prefetchable) [size=64K]
Region 3: Memory at ef600000 (64-bit, non-prefetchable) [size=256K]
...
Capabilities: [c0] MSI-X: Enable+ Count=16 Masked-
Vector table: BAR=1 offset=0000e000
PBA: BAR=1 offset=0000f000
Here the MSI-X data structures are placed on separate 4K pages at the
end of a 64KB BAR. If our host page size is 4K, we're likely fine,
but at 64KB page size, MSI-X emulation at that location prevents the
entire BAR from being directly mapped into the VM address space.
Overlapping performance sensitive registers then starts to be a very
likely scenario on such a platform. At this point, the user could
enable tracing on vfio_region_read and vfio_region_write to determine
more conclusively if device accesses are being trapped through QEMU.
Upon finding a device and platform in need of MSI-X relocation, the
next problem is how to choose target PCI BAR to host the MSI-X data
structures. A few key rules to keep in mind for this selection
include:
* There are only 6 BAR slots, bar0..bar5
* 64-bit BARs occupy two BAR slots, 'lspci -vvv' lists the first slot
* PCI BARs are always a power of 2 in size, extending == doubling
* The maximum size of a 32-bit BAR is 2GB
* MSI-X data structures must reside in an MMIO BAR
Using these rules, we can evaluate each BAR of the second example
device above as follows:
bar0: I/O port BAR, incompatible with MSI-X tables
bar1: BAR could be extended, incurring another 64KB of MMIO
bar2: Unavailable, bar1 is 64-bit, this register is used by bar1
bar3: BAR could be extended, incurring another 256KB of MMIO
bar4: Unavailable, bar3 is 64bit, this register is used by bar3
bar5: Available, empty BAR, minimum additional MMIO
A secondary optimization we might wish to make in relocating MSI-X
is to minimize the additional MMIO required for the device, therefore
we might test the available choices in order of preference as bar5,
bar1, and finally bar3. The original proposal for this feature
included an 'auto' option which would choose bar5 in this case, but
various drivers have been found that make assumptions about the
properties of the "first" BAR or the size of BARs such that there
appears to be no foolproof automatic selection available, requiring
known good combinations to be sourced from users. This patch is
pre-enabled for an 'auto' selection making use of a validated lookup
table, but no entries are yet identified.
Tested-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Tested-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
In order to enable TCE operations support in KVM, we have to inform
the KVM about VFIO groups being attached to specific LIOBNs. The KVM
already knows about VFIO groups, the only bit missing is which
in-kernel TCE table (the one with user visible TCEs) should update
the attached broups. There is an KVM_DEV_VFIO_GROUP_SET_SPAPR_TCE
attribute of the VFIO KVM device which receives a groupfd/tablefd couple.
This uses a new memory_region_iommu_get_attr() helper to get the IOMMU fd
and calls KVM to establish the link.
As get_attr() is not implemented yet, this should cause no behavioural
change.
Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Acked-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
The only exception are groups of numers separated by symbols
'.', ' ', ':', '/', like 'ab.09.7d'.
This patch is made by the following:
> find . -name trace-events | xargs python script.py
where script.py is the following python script:
=========================
#!/usr/bin/env python
import sys
import re
import fileinput
rhex = '%[-+ *.0-9]*(?:[hljztL]|ll|hh)?(?:x|X|"\s*PRI[xX][^"]*"?)'
rgroup = re.compile('((?:' + rhex + '[.:/ ])+' + rhex + ')')
rbad = re.compile('(?<!0x)' + rhex)
files = sys.argv[1:]
for fname in files:
for line in fileinput.input(fname, inplace=True):
arr = re.split(rgroup, line)
for i in range(0, len(arr), 2):
arr[i] = re.sub(rbad, '0x\g<0>', arr[i])
sys.stdout.write(''.join(arr))
=========================
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Acked-by: Cornelia Huck <cohuck@redhat.com>
Message-id: 20170731160135.12101-5-vsementsov@virtuozzo.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
With the move of some docs/ to docs/devel/ on ac06724a71,
no references were updated.
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
We traces its range, but we don't know whether it's a MAP/UNMAP. Let's
dump it as well.
Acked-by: Alex Williamson <alex.williamson@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
There are a number of unused trace events that
scripts/cleanup-trace-events.pl finds. The "hw/vfio/pci-quirks.c"
filename was typoed and "qapi/qapi-visit-core.c" was missing the qapi/
directory prefix.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-id: 20170126171613.1399-3-stefanha@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This patch converts VFIO PCI to realize function.
Also original initfn errors now are propagated using QEMU
error objects. All errors are formatted with the same pattern:
"vfio: %s: the error description"
Signed-off-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
New VFIO_SPAPR_TCE_v2_IOMMU type supports dynamic DMA window management.
This adds ability to VFIO common code to dynamically allocate/remove
DMA windows in the host kernel when new VFIO container is added/removed.
This adds a helper to vfio_listener_region_add which makes
VFIO_IOMMU_SPAPR_TCE_CREATE ioctl and adds just created IOMMU into
the host IOMMU list; the opposite action is taken in
vfio_listener_region_del.
When creating a new window, this uses heuristic to decide on the TCE table
levels number.
This should cause no guest visible change in behavior.
Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
[dwg: Added some casts to prevent printf() warnings on certain targets
where the kernel headers' __u64 doesn't match uint64_t or PRIx64]
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
This makes use of the new "memory registering" feature. The idea is
to provide the userspace ability to notify the host kernel about pages
which are going to be used for DMA. Having this information, the host
kernel can pin them all once per user process, do locked pages
accounting (once) and not spent time on doing that in real time with
possible failures which cannot be handled nicely in some cases.
This adds a prereg memory listener which listens on address_space_memory
and notifies a VFIO container about memory which needs to be
pinned/unpinned. VFIO MMIO regions (i.e. "skip dump" regions) are skipped.
The feature is only enabled for SPAPR IOMMU v2. The host kernel changes
are required. Since v2 does not need/support VFIO_IOMMU_ENABLE, this does
not call it when v2 is detected and enabled.
This enforces guest RAM blocks to be host page size aligned; however
this is not new as KVM already requires memory slots to be host page
size aligned.
Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
[dwg: Fix compile error on 32-bit host]
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
The kernel currently exposes the SR-IOV capability as read-only
through vfio-pci. This is sufficient to protect the host kernel, but
has the potential to confuse guests without further virtualization.
In particular, OVMF tries to size the VF BARs and comes up with absurd
results, ending with an assert. There's not much point in adding
virtualization to a read-only capability, so we simply hide it for
now. If the kernel ever enables SR-IOV virtualization, we should
easily be able to test it through VF BAR sizing or explicit flags.
Testing whether we should parse extended capabilities is also pulled
into the function to keep these assumptions in one place.
Tested-by: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Move all trace-events for files in the hw/vfio/ directory to
their own file.
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
Message-id: 1466066426-16657-30-git-send-email-berrange@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
