Am 2021-08-11 um 3:29 p.m. schrieb Alex Deucher:
On Wed, Aug 11, 2021 at 3:11 PM Ramesh Errabolu Ramesh.Errabolu@amd.com wrote:
Current implementation will disallow P2P DMA if the participating devices belong to different root complexes. Implementation allows this default behavior to be overridden for whitelisted devices. The patch adds an AMD host bridge to be whitelisted
Why do we need this? cpu_supports_p2pdma() should return true for all AMD Zen CPUs.
This is part of our on-going work to get P2P support upstream. We want to use pci_p2pdma_distance_many to determine whether P2P is possible between a pair of devices. This whitelist is used in this function. This will affect the P2P links reported in the topology and it will be double-checked in the BO mapping function to ensure a peer mapping is legal.
I think this change is a bit free of context at the moment, as we're still working on a few other loose ends for P2P support in our internal branch. I'm hoping we'll have a bigger patch series for upstreamable KFD P2P support ready in a few weeks. I also think we'll probably want to add a few more PCI IDs for other supported AMD root complexes.
Regards, Felix
Alex
Signed-off-by: Ramesh Errabolu Ramesh.Errabolu@amd.com
drivers/pci/p2pdma.c | 2 ++ 1 file changed, 2 insertions(+)
diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c index 196382630363..7003bb9faf23 100644 --- a/drivers/pci/p2pdma.c +++ b/drivers/pci/p2pdma.c @@ -305,6 +305,8 @@ static const struct pci_p2pdma_whitelist_entry { {PCI_VENDOR_ID_INTEL, 0x2032, 0}, {PCI_VENDOR_ID_INTEL, 0x2033, 0}, {PCI_VENDOR_ID_INTEL, 0x2020, 0},
/* AMD Host Bridge Devices */{PCI_VENDOR_ID_AMD, 0x1480, 0}, {}};
-- 2.31.1