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Re: [PATCH v3 2/4] vpci: allow queueing of mapping operations
- To: Stewart Hildebrand <stewart.hildebrand@xxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- From: Mykyta Poturai <Mykyta_Poturai@xxxxxxxx>
- Date: Thu, 2 Apr 2026 15:52:20 +0000
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- Cc: Roger Pau Monné <roger.pau@xxxxxxxxxx>
- Delivery-date: Thu, 02 Apr 2026 15:52:35 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
- Thread-index: AQHcuzsjSQhCcIF69U+TfmTRWDgaEbXL+uoA
- Thread-topic: [PATCH v3 2/4] vpci: allow queueing of mapping operations
On 3/24/26 05:04, Stewart Hildebrand wrote:
> Introduce vPCI BAR mapping task queue. Store information necessary in an
> array in struct vpci_vcpu to perform multiple p2m operations associated
> with single device.
>
> This is preparatory work for further changes that need to perform
> multiple unmap/map operations before returning to guest.
>
> At the moment, only a single slot is needed in the array. However, when
> multiple operations are queued and pending, there is a check in
> modify_bars() to skip BARs already in the requested state that is not
> accurate. Remove this check.
>
> Signed-off-by: Stewart Hildebrand <stewart.hildebrand@xxxxxxx>
> ---
> apply_map() and vpci_process_map_task() are very similar. Should we try
> to combine them into a single function?
>
> v2->v3:
> * base on ("vpci: Use pervcpu ranges for BAR mapping") from [1]
> * rework with fixed array of map/unmap slots
>
> [1]
> https://lore.kernel.org/xen-devel/cover.1772806036.git.mykyta_poturai@xxxxxxxx/T/#t
>
> v1->v2:
> * new patch
Hi everyone,
Would it be possible to move back to a dynamically allocated number of
tasks? This would help with mapping SR-IOV virtual functions a lot.
@Stewart @Roger, what are your thoughts?
Alternatively, I can continue with an approach described in SR-IOV
series, where VFs are handled separately. I figured out how to return to
do_softirq after mapping each VF, so it should not block the CPU for too
long.
--
Mykyta
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