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Re: [PATCH v2 10/11] vpci: Add initial support for virtual PCI bus topology

  • To: Jan Beulich <jbeulich@xxxxxxxx>
  • From: Oleksandr Andrushchenko <Oleksandr_Andrushchenko@xxxxxxxx>
  • Date: Wed, 29 Sep 2021 11:56:24 +0000
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  • Cc: "julien@xxxxxxx" <julien@xxxxxxx>, "sstabellini@xxxxxxxxxx" <sstabellini@xxxxxxxxxx>, Oleksandr Tyshchenko <Oleksandr_Tyshchenko@xxxxxxxx>, Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>, Artem Mygaiev <Artem_Mygaiev@xxxxxxxx>, "roger.pau@xxxxxxxxxx" <roger.pau@xxxxxxxxxx>, Bertrand Marquis <bertrand.marquis@xxxxxxx>, Rahul Singh <rahul.singh@xxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Oleksandr Andrushchenko <Oleksandr_Andrushchenko@xxxxxxxx>, Michal Orzel <michal.orzel@xxxxxxx>
  • Delivery-date: Wed, 29 Sep 2021 11:56:36 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
  • Thread-topic: [PATCH v2 10/11] vpci: Add initial support for virtual PCI bus topology

On 29.09.21 12:09, Jan Beulich wrote:
> On 29.09.2021 11:03, Oleksandr Andrushchenko wrote:
>> Sorry for top posting, but this is a general question on this 
>> patch/functionality.
>> Do you see we need to gate all this with CONFIG_HAS_VPCI_GUEST_SUPPORT
>> as this renders in somewhat dead code for x86 for now? I do think this still
>> needs to be in the common code though.
> I agree it wants to live in common code, but I'd still like the code to
> not bloat x86 binaries. Hence yes, I think there want to be
> "if ( !IS_ENABLED() )" early bailout paths or, whenever this isn't
> possible without breaking the build, respective #ifdef-s.

Then it needs to be defined as (xen/drivers/Kconfig):

     # vPCI guest support is only enabled for Arm now
     def_bool y if ARM
     depends on HAS_VPCI

Because it needs to be defined as "y" for Arm with vPCI support.

Otherwise it breaks the PCI passthrough feature, e.g. it compiles,

but the resulting binary behaves wrong.

Do you see this as an acceptable solution?

> Jan
Thank you,




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