Re: [PATCH v4 1/5] PCI/P2PDMA: Don't enforce ACS check for device functions of Intel GPUs

[Logan Gunthorpe <logang@deltatee.com>]

On 2025-09-15 01:21, Vivek Kasireddy wrote:
> Typically, functions of the same PCI device (such as a PF and a VF)
> share the same bus and have a common root port and the PF provisions
> resources for the VF. Given this model, they can be considered
> compatible as far as P2PDMA access is considered.
> 
> Currently, although the distance (2) is correctly calculated for
> functions of the same device, an ACS check failure prevents P2P DMA
> access between them. Therefore, introduce a small function named
> pci_devfns_support_p2pdma() to determine if the provider and client
> belong to the same device and facilitate P2PDMA between them by
> not enforcing the ACS check.
> 
> However, since it is hard to determine if the device functions of
> any given PCI device are P2PDMA compatible, we only relax the ACS
> check enforcement for device functions of Intel GPUs. This is
> because the P2PDMA communication between the PF and VF of Intel
> GPUs is handled internally and does not typically involve the PCIe
> fabric.
> 
> Cc: Bjorn Helgaas <bhelgaas@google.com>
> Cc: Logan Gunthorpe <logang@deltatee.com>
> Cc: <linux-pci@vger.kernel.org>
> Signed-off-by: Vivek Kasireddy <vivek.kasireddy@intel.com>

This looks good to me, thanks.

Reviewed-by: Logan Gunthorpe <logang@deltatee.com>