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Re: [PATCH v4 4/5] [FUTURE] xen/arm: enable vPCI for domUs
- To: Stewart Hildebrand <stewart.hildebrand@xxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Tue, 31 Oct 2023 17:17:28 +0100
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- Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>, Bertrand Marquis <bertrand.marquis@xxxxxxx>, Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>, Paul Durrant <paul@xxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx, Julien Grall <julien@xxxxxxx>
- Delivery-date: Tue, 31 Oct 2023 16:17:45 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 31.10.2023 15:15, Stewart Hildebrand wrote:
> On 10/31/23 09:17, Julien Grall wrote:
>> On 31/10/2023 11:03, Jan Beulich wrote:
>>> On 31.10.2023 00:52, Stewart Hildebrand wrote:
>>>> --- a/xen/drivers/passthrough/pci.c
>>>> +++ b/xen/drivers/passthrough/pci.c
>>>> @@ -1618,6 +1618,16 @@ int iommu_do_pci_domctl(
>>>> bus = PCI_BUS(machine_sbdf);
>>>> devfn = PCI_DEVFN(machine_sbdf);
>>>> + if ( IS_ENABLED(CONFIG_ARM) &&
>>>> + !is_hardware_domain(d) &&
>>>> + !is_system_domain(d) &&
>>>> + (!IS_ENABLED(CONFIG_HAS_VPCI_GUEST_SUPPORT) || !has_vpci(d))
>>>> )
>>>
>>> I don't think you need the explicit ARM check; that's redundant with
>>> checking !HAS_VPCI_GUEST_SUPPORT.
>
> Currently that is true. However, this is allowing for the possibility that we
> eventually may want to enable PCI passthrough for PVH domU using vPCI (e.g.
> hyperlaunch, or eliminating qemu backend), in which case we may want to
> enable CONFIG_HAS_VPCI_GUEST_SUPPORT=y on x86.
That's precisely why I'd like to see the ARM check go away here.
>>> It's also not really clear why you
>>> need to check for the system domain here.
>
> xl pci-assignable-add will assign the device to domIO, which doesn't have
> vPCI, but it is still a valid assignment. Perhaps an in code comment would be
> helpful for clarity?
And/or specifically check for DomIO, not any system domain.
Jan
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