On Tue, Oct 06, 2026 at 05:28:45PM -0500, Bjorn Helgaas wrote: > 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?
I'd say it does. Before this patch, we didn't return `bus_address` here nor took the P2P path. Thanks > > 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 > >
