[Qemu-devel] Virtual IOMMU is working for Windows VM?

[Qemu-devel] Virtual IOMMU is working for Windows VM?

[Jintack Lim]

Hi,

I wonder if vIOMMU is working for Windows VM?

I tried it with v2.11.0, but it didn't seem to work. I assume that seaBIOS
sets IOMMU on by default as is the case when I launched a Linux VM. But I
might be missing something. Can somebody shed some light on it?

Thanks,
Jintack

Re: [Qemu-devel] Virtual IOMMU is working for Windows VM?

[Peter Xu]

On Mon, Oct 22, 2018 at 12:22:02AM -0400, Jintack Lim wrote:
> Hi,
> 
> I wonder if vIOMMU is working for Windows VM?
> 
> I tried it with v2.11.0, but it didn't seem to work. I assume that seaBIOS
> sets IOMMU on by default as is the case when I launched a Linux VM. But I
> might be missing something. Can somebody shed some light on it?

Hi, Jintack,

I think at least the latest QEMU should work for Windows, but I don't
really run Windows that frequently.

What is the error you've encountered?  Have you tried the latest QEMU,
or switching Windows versions to try?

What I can remember about Windows is that Ladi had fixed a bug for
windows-only (8991c460be, "intel_iommu: relax iq tail check on
VTD_GCMD_QIE enable", 2017-07-03) but it should be even in 2.10 so I
guess it's not the problem you've encountered.

Regards,

-- 
Peter Xu

Re: [Qemu-devel] Virtual IOMMU is working for Windows VM?

[Jintack Lim]

On Mon, Oct 22, 2018 at 5:27 AM Peter Xu <peterx@redhat.com> wrote:
>
> On Mon, Oct 22, 2018 at 12:22:02AM -0400, Jintack Lim wrote:
> > Hi,
> >
> > I wonder if vIOMMU is working for Windows VM?
> >
> > I tried it with v2.11.0, but it didn't seem to work. I assume that seaBIOS
> > sets IOMMU on by default as is the case when I launched a Linux VM. But I
> > might be missing something. Can somebody shed some light on it?
>
> Hi, Jintack,
>

Thanks Peter,

> I think at least the latest QEMU should work for Windows, but I don't
> really run Windows that frequently.
>
> What is the error you've encountered?  Have you tried the latest QEMU,
> or switching Windows versions to try?

I ran Windows commands in Windows Powershell like below. Well, I guess
this is not the best way to check IOMMU presence, but couldn't find a
better way to do it.

$ (Get-VMHost).IovSupport
false
$ (Get-VMHost).IovSupportReasons
The chipset on the system does not do DMA remapping, ...

I just tried QEMU v3.0.0, but I see the same symptom. I'm using
Windows server 2016.  Unfortunately, trying another Windows version
would be hard for me at this point.

I just wonder if there's way to check if Vt-d is on in SeaBIOS?

>
> What I can remember about Windows is that Ladi had fixed a bug for
> windows-only (8991c460be, "intel_iommu: relax iq tail check on
> VTD_GCMD_QIE enable", 2017-07-03) but it should be even in 2.10 so I
> guess it's not the problem you've encountered.

I'm CCing Ladi, just in case he has some idea :)

Thanks,
Jintack

>
> Regards,
>
> --
> Peter Xu
>

Re: [Qemu-devel] Virtual IOMMU is working for Windows VM?

[Peter Xu]

On Mon, Oct 22, 2018 at 10:43:32AM -0400, Jintack Lim wrote:
> On Mon, Oct 22, 2018 at 5:27 AM Peter Xu <peterx@redhat.com> wrote:
> >
> > On Mon, Oct 22, 2018 at 12:22:02AM -0400, Jintack Lim wrote:
> > > Hi,
> > >
> > > I wonder if vIOMMU is working for Windows VM?
> > >
> > > I tried it with v2.11.0, but it didn't seem to work. I assume that seaBIOS
> > > sets IOMMU on by default as is the case when I launched a Linux VM. But I
> > > might be missing something. Can somebody shed some light on it?
> >
> > Hi, Jintack,
> >
> 
> Thanks Peter,
> 
> > I think at least the latest QEMU should work for Windows, but I don't
> > really run Windows that frequently.
> >
> > What is the error you've encountered?  Have you tried the latest QEMU,
> > or switching Windows versions to try?
> 
> I ran Windows commands in Windows Powershell like below. Well, I guess
> this is not the best way to check IOMMU presence, but couldn't find a
> better way to do it.
> 
> $ (Get-VMHost).IovSupport
> false
> $ (Get-VMHost).IovSupportReasons
> The chipset on the system does not do DMA remapping, ...
> 
> I just tried QEMU v3.0.0, but I see the same symptom. I'm using
> Windows server 2016.  Unfortunately, trying another Windows version
> would be hard for me at this point.
> 
> I just wonder if there's way to check if Vt-d is on in SeaBIOS?

I'm not sure whether SeaBIOS would enable VT-d or has any kind of
support of it at all even if the translation unit is provided.

> 
> >
> > What I can remember about Windows is that Ladi had fixed a bug for
> > windows-only (8991c460be, "intel_iommu: relax iq tail check on
> > VTD_GCMD_QIE enable", 2017-07-03) but it should be even in 2.10 so I
> > guess it's not the problem you've encountered.
> 
> I'm CCing Ladi, just in case he has some idea :)

Good idea, though I'm afraid the RH email could be stall though. :)

I can try to install one Windows Server 2016 some day but I cannot
really guarantee.  Feel free to try to debug it on your own :).
Basically I would consider to enable the IOMMU traces in intel_iommu.c
just like what you have done before when with the vfio-pci devices and
check out the log.  Normally we should see plenty of MMIOs to setup
the device and hopefully that would provide hint on what's wrong there.

Regards,

-- 
Peter Xu

Re: [Qemu-devel] Virtual IOMMU is working for Windows VM?

[Jintack Lim]

On Tue, Oct 23, 2018 at 9:25 AM Peter Xu <peterx@redhat.com> wrote:
>
> On Mon, Oct 22, 2018 at 10:43:32AM -0400, Jintack Lim wrote:
> > On Mon, Oct 22, 2018 at 5:27 AM Peter Xu <peterx@redhat.com> wrote:
> > >
> > > On Mon, Oct 22, 2018 at 12:22:02AM -0400, Jintack Lim wrote:
> > > > Hi,
> > > >
> > > > I wonder if vIOMMU is working for Windows VM?
> > > >
> > > > I tried it with v2.11.0, but it didn't seem to work. I assume that seaBIOS
> > > > sets IOMMU on by default as is the case when I launched a Linux VM. But I
> > > > might be missing something. Can somebody shed some light on it?
> > >
> > > Hi, Jintack,
> > >
> >
> > Thanks Peter,
> >
> > > I think at least the latest QEMU should work for Windows, but I don't
> > > really run Windows that frequently.
> > >
> > > What is the error you've encountered?  Have you tried the latest QEMU,
> > > or switching Windows versions to try?
> >
> > I ran Windows commands in Windows Powershell like below. Well, I guess
> > this is not the best way to check IOMMU presence, but couldn't find a
> > better way to do it.
> >
> > $ (Get-VMHost).IovSupport
> > false
> > $ (Get-VMHost).IovSupportReasons
> > The chipset on the system does not do DMA remapping, ...
> >
> > I just tried QEMU v3.0.0, but I see the same symptom. I'm using
> > Windows server 2016.  Unfortunately, trying another Windows version
> > would be hard for me at this point.
> >
> > I just wonder if there's way to check if Vt-d is on in SeaBIOS?
>
> I'm not sure whether SeaBIOS would enable VT-d or has any kind of
> support of it at all even if the translation unit is provided.
>

All right. I then assume the BIOS doesn't disable it as is the case
for Linux guest.

> >
> > >
> > > What I can remember about Windows is that Ladi had fixed a bug for
> > > windows-only (8991c460be, "intel_iommu: relax iq tail check on
> > > VTD_GCMD_QIE enable", 2017-07-03) but it should be even in 2.10 so I
> > > guess it's not the problem you've encountered.
> >
> > I'm CCing Ladi, just in case he has some idea :)
>
> Good idea, though I'm afraid the RH email could be stall though. :)

Ah.. :)

>
> I can try to install one Windows Server 2016 some day but I cannot
> really guarantee.  Feel free to try to debug it on your own :).
> Basically I would consider to enable the IOMMU traces in intel_iommu.c
> just like what you have done before when with the vfio-pci devices and
> check out the log.  Normally we should see plenty of MMIOs to setup
> the device and hopefully that would provide hint on what's wrong there.

Thanks. I will. Now that Linux guest can recognize vIOMMU well, hope I
can spot where things go wrong with Window guest hopefully!

Best,
Jintack

>
> Regards,
>
> --
> Peter Xu
>