On 29/04/24 6:10 pm, Cédric Le Goater wrote:
Hello Vinayak,
On 3/28/24 10:30, Cédric Le Goater wrote:
On 3/27/24 21:52, Alex Williamson wrote:
On Wed, 27 Mar 2024 16:11:37 -0400
"Michael S. Tsirkin" <mst@xxxxxxxxxx> wrote:
On Wed, Mar 27, 2024 at 11:39:15AM -0600, Alex Williamson wrote:
On Fri, 22 Mar 2024 12:12:10 +0530
Vinayak Kale <vkale@xxxxxxxxxx> wrote:
In case of migration, during restore operation, qemu checks config
space of the
pci device with the config space in the migration stream captured
during save
operation. In case of config space data mismatch, restore
operation is failed.
config space check is done in function get_pci_config_device(). By
default VSC
(vendor-specific-capability) in config space is checked.
Due to qemu's config space check for VSC, live migration is broken
across NVIDIA
vGPU devices in situation where source and destination host driver
is different.
In this situation, Vendor Specific Information in VSC varies on
the destination
to ensure vGPU feature capabilities exposed to the guest driver
are compatible
with destination host.
If a vfio-pci device is migration capable and vfio-pci vendor
driver is OK with
volatile Vendor Specific Info in VSC then qemu should exempt
config space check
for Vendor Specific Info. It is vendor driver's responsibility to
ensure that
VSC is consistent across migration. Here consistency could mean
that VSC format
should be same on source and destination, however actual Vendor
Specific Info
may not be byte-to-byte identical.
This patch skips the check for Vendor Specific Information in VSC
for VFIO-PCI
device by clearing pdev->cmask[] offsets. Config space check is
still enforced
for 3 byte VSC header. If cmask[] is not set for an offset, then
qemu skips
config space check for that offset.
Signed-off-by: Vinayak Kale <vkale@xxxxxxxxxx>
---
Version History
v2->v3:
- Config space check skipped only for Vendor Specific Info in
VSC, check is
still enforced for 3 byte VSC header.
- Updated commit description with live migration failure
scenario.
v1->v2:
- Limited scope of change to vfio-pci devices instead of all
pci devices.
hw/vfio/pci.c | 24 ++++++++++++++++++++++++
1 file changed, 24 insertions(+)
Acked-by: Alex Williamson <alex.williamson@xxxxxxxxxx>
A very reasonable way to do it.
Reviewed-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
Merge through the VFIO tree I presume?
Yep, Cédric said he´d grab it for 9.1. Thanks,
Could you please resend an update of this change adding a machine
compatibility property for migration ?
Sure, I'll address this in V4.
