Re: [PATCH V4] PCI/MSI: Skip MSI/MSI-X programming while the channel is offline

[sashiko-bot@kernel.org]

> The MSI-X Table lives in device MMIO space behind a BAR and the MSI Mask
> register in Configuration Space, so neither is reachable while the Link
> is down. While a Downstream Port has the Link contained by DPC it
> completes these accesses with Unsupported Request, and reads return all
> ones.
> 
> If the upstream Root Port implements the RP Extensions for DPC, it
> additionally reports that UR completion as an RP PIO error and triggers a
> second containment event, this time at the Root Port, which contains
> every device below it. So a contained Link on one Downstream Port turns
> into a far wider outage that takes down unrelated devices.
> 
> pci_free_irq_vectors() is called from driver error_detected() and
> prepare-for-reset callbacks, i.e. while the Link is contained and before
> the reset and the pci_restore_state() that follows it, and it masks every
> [ ... ]
> 
> This does not attempt to make every Configuration Space access safe
> while the Link is contained.
> 
> Signed-off-by: Vidya Sagar <vidyas@nvidia.com>

Sashiko has reviewed this patch and found no issues. It looks great!

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Sashiko AI review · https://sashiko.dev/#/patchset/20260909164908.2562818-1-vidyas@nvidia.com?part=1