Re: [PATCH 06/13] PCI: Account for ACS egress control in isolation checks

[Logan Gunthorpe]

On 2026-08-02 09:09, Leon Romanovsky wrote:
> From: Leon Romanovsky <leonro@xxxxxxxxxx>
> 
> 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.
> 
> Signed-off-by: Leon Romanovsky <leonro@xxxxxxxxxx>

Reviewed-by: Logan Gunthorpe <logang@xxxxxxxxxxxx>