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Re: [XEN PATCH v13 2/6] x86/pvh: Allow (un)map_pirq when dom0 is PVH
- To: Jan Beulich <jbeulich@xxxxxxxx>
- From: "Chen, Jiqian" <Jiqian.Chen@xxxxxxx>
- Date: Tue, 20 Aug 2024 06:12:51 +0000
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- Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, George Dunlap <gwd@xxxxxxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Anthony PERARD <anthony@xxxxxxxxxxxxxx>, Juergen Gross <jgross@xxxxxxxx>, "Daniel P . Smith" <dpsmith@xxxxxxxxxxxxxxxxxxxx>, "Hildebrand, Stewart" <Stewart.Hildebrand@xxxxxxx>, "Huang, Ray" <Ray.Huang@xxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>, "Chen, Jiqian" <Jiqian.Chen@xxxxxxx>
- Delivery-date: Tue, 20 Aug 2024 06:13:02 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
- Thread-index: AQHa78ytu3Dw7+A5rUaTPQAvAsIAxbIuTvuAgAHk7QA=
- Thread-topic: [XEN PATCH v13 2/6] x86/pvh: Allow (un)map_pirq when dom0 is PVH
On 2024/8/19 17:08, Jan Beulich wrote:
> On 16.08.2024 13:08, Jiqian Chen wrote:
>> If run Xen with PVH dom0 and hvm domU, hvm will map a pirq for
>> a passthrough device by using gsi, see qemu code
>> xen_pt_realize->xc_physdev_map_pirq and libxl code
>> pci_add_dm_done->xc_physdev_map_pirq. Then xc_physdev_map_pirq
>> will call into Xen, but in hvm_physdev_op, PHYSDEVOP_map_pirq
>> is not allowed because currd is PVH dom0 and PVH has no
>> X86_EMU_USE_PIRQ flag, it will fail at has_pirq check.
>>
>> So, allow PHYSDEVOP_map_pirq when dom0 is PVH and also allow
>> iPHYSDEVOP_unmap_pirq for the removal device path to unmap pirq.
>> So that the interrupt of a passthrough device can be successfully
>> mapped to pirq for domU with a notion of PIRQ when dom0 is PVH.
>>
>> To exposing the functionality to wider than (presently) necessary
>> audience(like PVH domU), so it doesn't add any futher restrictions.
>
> The code change is fine, but I'm struggling with this sentence. I can't
> really derive what you're trying to say.
Ah, I wanted to explain why this path not add any further restrictions, then
used your comments of last version.
How do I need to change this explanation?
>
>> And there already are some senarios for domains without
>> X86_EMU_USE_PIRQ to use these functions.
>
> Are there? If so, pointing out an example may help.
If I understand correctly, Roger mentioned that PIRQs is disable by default for
HVM guest("hvm_pirq=0") and passthrough device to guest.
In this scene, guest doesn't have PIRQs, but it still needs this hypercall.
>
> Jan
--
Best regards,
Jiqian Chen.
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