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

[Jintack Lim]

Adding CC and some more information.

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?
>
> Thanks,
> Jintack