On Thu, Oct 01, 2026 at 02:55:18PM +0300, Leon Romanovsky wrote: > From: Leon Romanovsky <[email protected]> > > A Downstream Port with ACS Direct Translated P2P enabled routes a Request > whose Address Type is Translated "to the peer Egress Port without > redirection, regardless of ACS P2P Request Redirect and ACS P2P Egress > Control", per PCIe r7.0 sec 6.12.3. P2PDMA assumes every Request carries an > Untranslated address, so it sends an ATS client through the host bridge > even where the fabric would route it straight to the peer.
"sends an ATS client through the host bridge" -- I assume this really means "we told the caller that Requests would be routed through the host bridge" when in reality they wouldn't? I don't think this actually changes any routing in the fabric, does it? So essentially we told the caller that P2P between A and B was, e.g., 5 hops when it was really only 2? > Add PCI_P2PDMA_TLP_TRANSLATED and consult Direct Translated P2P for the > Requests it describes. > > Reviewed-by: Logan Gunthorpe <[email protected]> > Tested-by: Tushar Dave <[email protected]> > Signed-off-by: Leon Romanovsky <[email protected]> > --- > drivers/pci/p2pdma.c | 9 +++++++++ > 1 file changed, 9 insertions(+) > > diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c > index 569a74de3b3a..3fd2cb8d16f0 100644 > --- a/drivers/pci/p2pdma.c > +++ b/drivers/pci/p2pdma.c > @@ -548,6 +548,15 @@ pci_acs_p2pdma_request(u16 ctrl, unsigned int tlp_flags) > */ > if (ctrl & PCI_ACS_TB) > return PCI_ACS_P2PDMA_BLOCKED; > + > + /* > + * PCIe r7.0 sec 6.12.3: ACS Direct Translated P2P routes a > + * Request carrying a Translated address to the peer "without > + * redirection, regardless of ACS P2P Request Redirect and ACS > + * P2P Egress Control settings". > + */ > + if (ctrl & PCI_ACS_DT) > + return PCI_ACS_P2PDMA_DIRECT; > } > > return ctrl & (PCI_ACS_RR | PCI_ACS_EC) ? > > -- > 2.55.0 >
