[vfio-users] Physical disk passthrough and OVMF

Blank Field ihatethisfield at gmail.com
Thu Mar 24 22:10:23 UTC 2016


Hello again, fellow subscribers.

Since 4.3.X kernels I am experiencing some strange problems with disk IO.

I am passing through the whole /dev/sda(since i also dualboot into
that system for some weird software or hardware) to my VM, and since
recent versions of kernel the VM gets stuck in an endless loop,
consuming 100% one core.

The ISA debug console says stuff like:
PartitionValidMbr: Bad MBR partition size EndingLBA(D99299D3) > LastLBA(31FFF)

The thing is that the disk in question has nothing to do with MBR, it
is formatted into GPT.
I can't pinpoint the source of that weird D99299D3 number.

That kind of error happens for every partition detected.

Device          Start        End    Sectors   Size Type
/dev/sda1        2048 1171875000 1171872953 558.8G Microsoft basic data
/dev/sda2  1171875840 1172080639     204800   100M EFI System
/dev/sda3  1172080640 1172342783     262144   128M Microsoft reserved
/dev/sda4  1172342784 1465145343  292802560 139.6G Microsoft basic data
/dev/sda5  1465145344 1953525134  488379791 232.9G Microsoft basic data
That looks like a valid partition table for me. Moreover, the fact
that i am able to boot an UEFI-capable system bare-metal confirms that
the partition table is correct.

I remember i've seen some related messages on the list in february or
something, but they only stated the existence of this error.

Have any of you seen stuff like that? If so, how do you live with it?

Maybe i should write to edk2-devel mailing list for this, because it
isn't much related to VFIO, but normal qemu folks rarely sacrifice the
whole disk to a VM.

Versions:
QEMU emulator version 2.4.1 (qemu-2.4.1-7.fc23)
kernel 4.4.5-300.fc23.x86_64(doesn't matter much from 4.3.X)
edk2.git-0-20160311.b1594.gf6326d1.x86_64




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