[Qemu-discuss] Corruption on Windows VMs when running 4.10+ kernel

[Tobias Schramm]

Hi,

I can confirm that there is an issue with Qemu 2.12 and Windows
guests. The issue may also extend to Linux guests but I did not
observe it there yet.

The issue seems to be that sometimes disk IO stalls for up to a few
minutes. On my Windows 7 guests I can observe 0 Bytes/s disk I/O while
there is 100% Highest Active Time in resource monitor. Changing the
cache mode has no effect.

Reverting to qemu 2.11.1 fixes the issue for me.

Guest:
OS: Windows 7

Host:
Qemu 2.12.0
Linux 4.16.3
cmdline:
initrd=\initramfs-linux-4.16.3.img rw intel_iommu=on
pci-stub.ids=10de:0fb0,10de:0e0f video=efifb:off kvm.ignore_msrs=1
kvm-intel.nested=1 i915.enable_gvt=1

qemu-command:

/usr/local/bin/qemu-system-x86_64 \
-machine q35 `# Chipset` \
-cpu host,kvm=off,hv_vendor_id=deadbeef1337 `# Emulate host CPU
features but mask kvm flag, set fake vendor id` \
-smp sockets=1,cores=4,threads=2 `# Set cpu layout` \
-enable-kvm `# Enable kvm for performance > 0` \
-rtc base=localtime `# Ensure that windows gets the correct timezone` \
-drive if=pflash,format=raw,readonly,file=firmware/201711/OVMF_CODE-with-csm.fd
`# UEFI rom image` \
-drive if=pflash,format=raw,file=firmware/201711/OVMF_VARS-with-csm-win7.fd
`# EFI vars` \
-m 16384 `# RAM` \
-drive file=win7.img,format=raw,index=0,media=disk `# Main disk image` \
-drive file=win7_old.img,format=raw,index=1,media=disk `# Old disk image` \
-device virtio-blk-pci,drive=games -drive
if=none,id=games,file=/dev/sda,format=raw `# Virtio drive passthrough
for games` \
-device ich9-usb-uhci3,id=uhci `# Emulate USB uhci controller` \
-device usb-ehci,id=ehci `# Emulate USB ehci controller` \
-device nec-usb-xhci,id=xhci `# Emulate xhci controller` \
-nographic `# Don't try to spawn graphics on my shell` \
-vga none `# Don't emulate any video devices` \
-device vfio-pci,host=04:00.0 `# Pass through physical PCIe USB 3.0 SS
controller` \
-device vfio-pci,host=01:00.0 `# Pass through GPU` \
-netdev bridge,br=br-vms,id=net0 -device
virtio-net-pci,netdev=net0,mac=42:13:37:42:42:42 \
-serial none `# Don't give me the serial port of the guest as stdout/-in`


Regards,
Tobias