Re: [PATCH v4 08/18] PCI: Account for Direct Translated P2P in ACS isolation checks

On 2026-08-21 13:38, Leon Romanovsky wrote:
> From: Leon Romanovsky <[email protected]>
> 
> PCIe r7.0, sec 6.12.3:
> 
>   peer-to-peer Memory Requests whose Address Type (AT) field indicates a
>   Translated address must be routed to the peer Port/Function without
>   redirection, regardless of ACS P2P Request Redirect and ACS P2P Egress
>   Control settings.
> 
> Request Redirect therefore does not isolate devices below a Port with
> ACS Direct Translated P2P enabled.
> 
> Sec 6.12.1.1 makes such a Request an ACS Violation once Translation
> Blocking is enabled, and that error "must take precedence over ... ACS
> P2P control mechanisms". Report isolation only in that case. Without
> Translation Blocking, devices below such a Port now share an IOMMU
> group.
> 
> This only holds for a caller that needs Request Redirect to isolate
> peers. pci_enable_pasid() asks for Request Redirect for a different
> reason: a Request carrying a PASID is routed by address alone (sec
> 2.2.10.4), so it has to be redirected Upstream to reach the translation
> agent. Direct Translated P2P says nothing about that, because a
> Translated Request already carries an address the agent produced for
> that PASID (sec 10.1.3).
> 
> Give pci_acs_enabled() and pci_acs_path_enabled() a scope so each caller
> states which Requests its answer has to cover, and apply the rule above
> only for PCI_ACS_SCOPE_ALL.
> 
> pci_acs_flags_enabled() and the Intel SPT PCH quirk both need the rule,
> so it lives in pci_acs_rr_ineffective().
> 
> Tested-by: Tushar Dave <[email protected]>
> Fixes: ad805758c0eb ("PCI: add ACS validation utility")
> Signed-off-by: Leon Romanovsky <[email protected]>

Looks, ok to me:

Reviewed-by: Logan Gunthorpe <[email protected]>