Re: [PATCH v4 10/18] PCI: Account for ACS egress control in isolation checks

[sashiko-bot@kernel.org]

> From: Leon Romanovsky <leonro@nvidia.com>
> 
> pci_acs_enabled() treats P2P Request Redirect as effective whenever its
> control bit is set. PCIe r7.0, sec 6.12.3, table 6-11 lets an enabled
> Egress Control Vector override it: a clear vector bit routes the request
> directly.
> 
> IOMMU grouping uses this check to prove peer requests cannot bypass the
> IOMMU, but cannot know every applicable vector bit, so Request Redirect
> gives no such guarantee while Egress Control is enabled.
> 
> Report Request Redirect as ineffective there, merging the devices into
> one IOMMU group, and report no isolation when the register cannot be
> read. Apply the same rule to the Intel SPT PCH quirk.
> 
> Unlike Direct Translated P2P this holds for an Untranslated Request too,
> so it applies in both scopes. pci_enable_pasid() therefore fails on a
> path where a port has Egress Control enabled, because Request Redirect
> no longer shows that a Request carrying a PASID reaches the translation
> agent.
> 
> Tested-by: Tushar Dave <tdave@nvidia.com>
> Fixes: ad805758c0eb ("PCI: add ACS validation utility")
> Reviewed-by: Logan Gunthorpe <logang@deltatee.com>
> Signed-off-by: Leon Romanovsky <leonro@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/20260821-fix-p2p-acs-v4-0-v4-0-94426b96de73@nvidia.com?part=10