On Thu, Oct 01, 2026 at 02:55:16PM +0300, Leon Romanovsky wrote: > From: Leon Romanovsky <[email protected]> > > ACS P2P Completion Redirect leaves Completions carrying the Relaxed > Ordering attribute alone. PCIe r7.0 sec 6.12.1.1 redirects only those "that > do not have the Relaxed Ordering Attribute bit set", and sec 7.7.12.5 > describes the enable bit as "applicable only to Completions whose Relaxed > Ordering Attribute is clear". P2PDMA reports one answer for every kind of > TLP, so a client whose provider returns such Completions is sent through > the host bridge for a redirect that never happens to it.
I guess pci_acs_p2pdma_completion() returned PCI_ACS_P2PDMA_REDIRECT even for RO Completions? But that didn't change the hardware behavior -- maybe the caller *thought* Completions were routed through the host bridge, but they actually weren't. I kind of lost the plot here. What does the caller do with this information? I don't think a device is *required* to set RO even when it is enabled, and it may set RO on some transactions but not others. > Add enum pci_p2pdma_tlp_flags and let a caller state that property. > > Reviewed-by: Logan Gunthorpe <[email protected]> > Tested-by: Tushar Dave <[email protected]> > Signed-off-by: Leon Romanovsky <[email protected]> > --- > drivers/pci/p2pdma.c | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c > index 43e225cc5735..1fadef6d0609 100644 > --- a/drivers/pci/p2pdma.c > +++ b/drivers/pci/p2pdma.c > @@ -544,11 +544,15 @@ pci_acs_p2pdma_request(u16 ctrl, unsigned int tlp_flags) > /* > * Decide how a peer-to-peer Completion at an ACS-capable ingress port > routes. > * PCIe r7.0 sec 6.12.1.1: no ACS control other than P2P Completion Redirect > - * affects a Completion. > + * affects a Completion, and that one leaves Completions carrying the Relaxed > + * Ordering attribute alone. > */ > static enum pci_acs_p2pdma_state > pci_acs_p2pdma_completion(u16 ctrl, unsigned int tlp_flags) > { > + if (tlp_flags & PCI_P2PDMA_TLP_RELAXED_CPL) > + return PCI_ACS_P2PDMA_DIRECT; > + > return ctrl & PCI_ACS_CR ? PCI_ACS_P2PDMA_REDIRECT : > PCI_ACS_P2PDMA_DIRECT; > } > > -- > 2.55.0 >
