Re: [Qemu-discuss] DMAR errors with iommu emulation enabled

[Jintack Lim]

Thanks Alex, I appreciate your help.

On Tue, Feb 7, 2017 at 12:09 PM, Alex Williamson
<address@hidden> wrote:
> On Tue, 7 Feb 2017 11:46:57 -0500
> Jintack Lim <address@hidden> wrote:
>
>> Adding CC and some more information.
>
> $ ./scripts/get_maintainer.pl -f ./hw/i386/intel_iommu.c
> get_maintainer.pl: No maintainers found, printing recent contributors.
> get_maintainer.pl: Do not blindly cc: them on patches!  Use common sense.

Oh, I got it. Thanks!

>
> "Michael S. Tsirkin" <address@hidden> (commit_signer:54/35=100%)
> Peter Xu <address@hidden> (commit_signer:28/35=80%)
> Paolo Bonzini <address@hidden> (commit_signer:6/35=17%)
> Jason Wang <address@hidden> (commit_signer:5/35=14%)
> "Radim Krčmář" <address@hidden> (commit_signer:5/35=14%)
> address@hidden (open list:All patches CC here)
>
>> On Tue, Feb 7, 2017 at 5:07 AM, Jintack Lim <address@hidden> wrote:
>> > Hi,
>> >
>> > I'm getting DMAR errors during VM booting when I enable the iommu
>> > emulation for the VM. I was not able to complete booting since the VM
>> > gets really slow and just keep printing the error message (sym0:
>> > unexpected disconnect) at a speed of one character per second.
>> >
>> > I have enabled the iommu emulation, but didn't assign any device to the VM.
>> >
>> > This is the kernel log from the VM
>>
>> I'm using 4.6.0-rc5+ kernel for the host and the VM.
>>
>> Here's the full kernel log from the VM.
>> https://paste.ubuntu.com/23948597/
>>
>> >
>> > [    6.087794] sym0: SCSI BUS has been reset.
>> > [    6.087960] DMAR: DRHD: handling fault status reg 2
>> > [    6.088001] DMAR: DMAR:[DMA Read] Request device [04:03.0] fault
>> > addr fe281000
>> > [    6.088001] DMAR:[fault reason 06] PTE Read access is not set
>> > [    6.090513] scsi host1: sym-2.2.3
>> > [    6.090567] sym0: unexpected disconnect
>> > [    8.814929] sym0: unexpected disconnect
>> > [   11.670251] sym0: unexpected disconnect
>> >
>> > I enabled iommu in the host (intel_iommu=on). I also enabled iommu in
>> > the guest AND gave this option to the qemu (-device intel-iommu). I'm
>> > using qemu 2.8.0 and libvirt 3.0.0.
>> > I used <qemu:commandline> in libvirt xml to enable iommu emulation.
>> > Here's the full libvirt xml.
>> > http://paste.ubuntu.com/23946803/
>> >
>> > I did lspci -vvv and 04:03:0 is scsi device. Unfortunately, I lost
>> > that information, and can't boot the VM now. I'll add this information
>> > later if necessary.
>>
>> This is information about 04:03:0
>> I got this from the another identical VM but not with the iommu emulation.
>>
>> address@hidden:~# lspci -vvs 04:03.0
>> 04:03.0 SCSI storage controller: LSI Logic / Symbios Logic 53c895a
>> Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr-
>> Stepping- SERR+ FastB2B- DisINTx-
>> Status: Cap- 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort-
>> <TAbort- <MAbort- >SERR- <PERR- INTx-
>> Latency: 255, Cache Line Size: 64 bytes
>> Interrupt: pin A routed to IRQ 23
>> Region 0: I/O ports at c000 [size=256]
>> Region 1: Memory at fe284000 (32-bit, non-prefetchable) [size=1K]
>> Region 2: Memory at fe280000 (32-bit, non-prefetchable) [size=8K]
>> Kernel driver in use: sym53c8xx
>>
>> >
>> > Any thoughts why this happens and how to fix?
>
> Try a different disk controller in the VM?  Running virtual VT-d can't
> automatically fix guest drivers that don't handle devices behind an
> IOMMU correctly.  I don't know if that's the case, but I imagine 53c895a
> has probably never been tested w/ VT-d emulation.

Ok, I'll try another disk controller. If someone can suggest other
disk controller which is working well with the iommu emulation, then
it would be great. I guess I got the controller by using this option
in virsh-install (--disk=/temp-space/guest50.img,size=10,bus=scsi),
but not 100% sure.

> Note that when you
> do get to the point off assigning a device to the VM, you're going to
> need to build your own QEMU with patches from the mailing list, or
> maybe wait a few days and they might make it to the git tree.  Thanks,

I'm afraid I understand this. I was able to assign a network device to
the VM without the iommu emulation. If I want to assign a network
device to the VM with the iommu emulation, then I need to apply
patches from the mailing list?

Thanks,
Jintack

>
> Alex
>