PCI passthrough support for PVH mode

PCI passthrough support for PVH mode

[tosher 1]

Hi,

Back in the year 2020, I was inquiring into the status of PCI passthrough support for PVH guests. At that time, Arm people were working on using vPCI for guest VMs. The expectation was to port that implementation to x86 once ready.

I was wondering if there is any update on this. Does Xen support PCI passthrough for PVH mode yet? Please let me know.

Thanks,
Mehrab

Re: PCI passthrough support for PVH mode

[Jan Beulich]

On 06.02.2022 06:59, tosher 1 wrote:
> Back in the year 2020, I was inquiring into the status of PCI passthrough support for PVH guests. At that time, Arm people were working on using vPCI for guest VMs. The expectation was to port that implementation to x86 once ready.
> 
> I was wondering if there is any update on this. Does Xen support PCI passthrough for PVH mode yet? Please let me know.

The Arm work is still WIP, and in how far it's going to be straightforward to
re-use that code for x86 is still unclear (afaict at least).

Jan

Re: PCI passthrough support for PVH mode

[tosher 1]

Hi Jan,

Thanks for letting me know this status.

I am wondering if PCI passthrough is at least available in Arm for other virtualization modes like PV, HVM, or PVHVM. For example, is it possible for someone to attach a PCI device to a guest domain on an Arm machine and use that domain as a driver domain, like we can do with the Xen on x86?

Please let me know.

Regards,
Mehrab




On Monday, February 7, 2022, 02:57:45 AM EST, Jan Beulich <jbeulich@suse.com> wrote: 





On 06.02.2022 06:59, tosher 1 wrote:

> Back in the year 2020, I was inquiring into the status of PCI passthrough support for PVH guests. At that time, Arm people were working on using vPCI for guest VMs. The expectation was to port that implementation to x86 once ready.
> 
> I was wondering if there is any update on this. Does Xen support PCI passthrough for PVH mode yet? Please let me know.


The Arm work is still WIP, and in how far it's going to be straightforward to
re-use that code for x86 is still unclear (afaict at least).

Jan

Re: PCI passthrough support for PVH mode

[Jan Beulich]

On 10.02.2022 08:22, tosher 1 wrote:
> I am wondering if PCI passthrough is at least available in Arm for other virtualization modes like PV, HVM, or PVHVM. For example, is it possible for someone to attach a PCI device to a guest domain on an Arm machine and use that domain as a driver domain, like we can do with the Xen on x86?

Which "other virtualization modes" are you aware of on Arm? (PVHVM is not
really a "mode" anyway, but more like a badly named marketing thing.)

Jan

Re: PCI passthrough support for PVH mode

[Bertrand Marquis]

Hi Mihrab,

> On 10 Feb 2022, at 07:22, tosher 1 <akm2tosher@yahoo.com> wrote:
> 
> Hi Jan,
> 
> Thanks for letting me know this status.
> 
> I am wondering if PCI passthrough is at least available in Arm for other virtualization modes like PV, HVM, or PVHVM. For example, is it possible for someone to attach a PCI device to a guest domain on an Arm machine and use that domain as a driver domain, like we can do with the Xen on x86?

On arm there is only one virtualization mode which is equivalent to x86 HVM.

Regarding PCI passthrough on arm, this is currently a work in progress that is being upstream so it is not available for now.
Once it will be merged in Xen, it will be possible to assign a PCI device to a guest so you could then make a “driver domain” using the functionality.

Regards
Bertrand

> 
> Please let me know.
> 
> Regards,
> Mehrab
> 
> 
> 
> 
> On Monday, February 7, 2022, 02:57:45 AM EST, Jan Beulich <jbeulich@suse.com> wrote: 
> 
> 
> 
> 
> 
> On 06.02.2022 06:59, tosher 1 wrote:
> 
>> Back in the year 2020, I was inquiring into the status of PCI passthrough support for PVH guests. At that time, Arm people were working on using vPCI for guest VMs. The expectation was to port that implementation to x86 once ready.
>> 
>> I was wondering if there is any update on this. Does Xen support PCI passthrough for PVH mode yet? Please let me know.
> 
> 
> The Arm work is still WIP, and in how far it's going to be straightforward to
> re-use that code for x86 is still unclear (afaict at least).
> 
> Jan
> 
> 
> 

Re: PCI passthrough support for PVH mode

[tosher 1]

Hi Bertrand and Jan,

I thought PCI passthrough was a WIP only for PVH mode on Arm and x86. However, it seems there are some differences. Thanks for the clarifications.

Regards,
Mehrab






On Thursday, February 10, 2022, 03:32:19 AM EST, Bertrand Marquis <bertrand.marquis@arm.com> wrote: 





Hi Mihrab,

> On 10 Feb 2022, at 07:22, tosher 1 <akm2tosher@yahoo.com> wrote:
> 
> Hi Jan,
> 
> Thanks for letting me know this status.
> 
> I am wondering if PCI passthrough is at least available in Arm for other virtualization modes like PV, HVM, or PVHVM. For example, is it possible for someone to attach a PCI device to a guest domain on an Arm machine and use that domain as a driver domain, like we can do with the Xen on x86?

On arm there is only one virtualization mode which is equivalent to x86 HVM.

Regarding PCI passthrough on arm, this is currently a work in progress that is being upstream so it is not available for now.
Once it will be merged in Xen, it will be possible to assign a PCI device to a guest so you could then make a “driver domain” using the functionality.

Regards
Bertrand


> 
> Please let me know.
> 
> Regards,
> Mehrab
> 
> 
> 
> 
> On Monday, February 7, 2022, 02:57:45 AM EST, Jan Beulich <jbeulich@suse.com> wrote: 
> 
> 
> 
> 
> 
> On 06.02.2022 06:59, tosher 1 wrote:
> 
>> Back in the year 2020, I was inquiring into the status of PCI passthrough support for PVH guests. At that time, Arm people were working on using vPCI for guest VMs. The expectation was to port that implementation to x86 once ready.
>> 
>> I was wondering if there is any update on this. Does Xen support PCI passthrough for PVH mode yet? Please let me know.
> 
> 
> The Arm work is still WIP, and in how far it's going to be straightforward to
> re-use that code for x86 is still unclear (afaict at least).
> 
> Jan
> 
> 
> 

Re: PCI passthrough support for PVH mode

[Julien Grall]

Hi Bertrand,

On 10/02/2022 08:32, Bertrand Marquis wrote:
>> On 10 Feb 2022, at 07:22, tosher 1 <akm2tosher@yahoo.com> wrote:
>>
>> Hi Jan,
>>
>> Thanks for letting me know this status.
>>
>> I am wondering if PCI passthrough is at least available in Arm for other virtualization modes like PV, HVM, or PVHVM. For example, is it possible for someone to attach a PCI device to a guest domain on an Arm machine and use that domain as a driver domain, like we can do with the Xen on x86?
> 
> On arm there is only one virtualization mode which is equivalent to x86 HVM.

I would like to correct this. Arm guests are more equivalent to x86 PVH 
than HVM. For more details, see:

https://wiki.xenproject.org/wiki/Understanding_the_Virtualization_Spectrum#PVH:

This is also why we need a brand new solution for PCI passthrough rather 
than piggying back on what was done on HVM in QEMU :).

Cheers,

-- 
Julien Grall

Re: PCI passthrough support for PVH mode

[tosher 1]

Hi Julien,

Thanks for the clarification!

Regrads,
Mehrab






On Thursday, February 10, 2022, 06:12:53 PM EST, Julien Grall <julien@xen.org> wrote: 





Hi Bertrand,

On 10/02/2022 08:32, Bertrand Marquis wrote:
>> On 10 Feb 2022, at 07:22, tosher 1 <akm2tosher@yahoo.com> wrote:
>>
>> Hi Jan,
>>
>> Thanks for letting me know this status.
>>
>> I am wondering if PCI passthrough is at least available in Arm for other virtualization modes like PV, HVM, or PVHVM. For example, is it possible for someone to attach a PCI device to a guest domain on an Arm machine and use that domain as a driver domain, like we can do with the Xen on x86?
> 
> On arm there is only one virtualization mode which is equivalent to x86 HVM.


I would like to correct this. Arm guests are more equivalent to x86 PVH 
than HVM. For more details, see:

https://wiki.xenproject.org/wiki/Understanding_the_Virtualization_Spectrum#PVH:

This is also why we need a brand new solution for PCI passthrough rather 
than piggying back on what was done on HVM in QEMU :).

Cheers,

-- 
Julien Grall