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Re: SR-IOV: do we need to virtualize in Xen or rely on Dom0?

  • To: Jan Beulich <jbeulich@xxxxxxxx>
  • From: Oleksandr Andrushchenko <Oleksandr_Andrushchenko@xxxxxxxx>
  • Date: Thu, 10 Jun 2021 11:45:49 +0000
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  • Cc: "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>
  • Delivery-date: Thu, 10 Jun 2021 11:46:01 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
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  • Thread-topic: SR-IOV: do we need to virtualize in Xen or rely on Dom0?

Hi, Jan!

On 10.06.21 13:48, Jan Beulich wrote:
> On 10.06.2021 12:01, Oleksandr Andrushchenko wrote:
>> On 10.06.21 10:54, Roger Pau Monné wrote:
>>> OTOH if we properly trap accesses to the SR-IOV capability (like it
>>> was proposed in [1] from your references) we won't have to modify OSes
>>> that want to run as hardware domains in order to handle SR-IOV devices.
>> Out of curiosity, could you please name a few? I do understand that
>> we do want to support unmodified OSes and this is indeed important.
>> But, still what are the other OSes which do support Xen + PCI passthrough?
> I think Roger saying "want" meant to cover ones which currently don't,
> and which would have to undergo more extensive changes if they were to
> be enabled.

Fair enough. Do you think we would also need to re-work the existing code

in Xen to support normal devices (not SR-IOV), e.g. we currently rely on

PHYSDEVOP_XXX and other Linux specifics. And even if SR-IOV is implemented

in Xen this won't allow those OSes to stay unmodified, including FreeBSD.

Is my understanding correct?

> Jan
Thank you,




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