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
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}, {} };
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.
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
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
On Wed, Aug 11, 2021 at 4:50 PM Felix Kuehling felix.kuehling@amd.com wrote:
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.
We don't need to keep adding AMD root complexes. You must be using an older kernel or something. All root complexes on all Zen platforms support P2P DMA. See:
commit dea286bb71baded7d2fb4f090e3b9fd2c1ccac58 Author: Logan Gunthorpe logang@deltatee.com Date: Wed Jul 29 17:18:44 2020 -0600
PCI/P2PDMA: Allow P2PDMA on AMD Zen and newer CPUs
Allow P2PDMA if the CPU vendor is AMD and family is 0x17 (Zen) or greater.
[bhelgaas: commit log, simplify #if/#else/#endif] Link: https://lore.kernel.org/r/20200729231844.4653-1-logang@deltatee.com Signed-off-by: Logan Gunthorpe logang@deltatee.com Signed-off-by: Bjorn Helgaas bhelgaas@google.com Reviewed-by: Alex Deucher alexander.deucher@amd.com Cc: Christian König christian.koenig@amd.com Cc: Huang Rui ray.huang@amd.com
Alex
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
I will investigate it further. I am using DKMS-5.11 branch. The codebase I am using to build has the right definition i.e. allow P2PDMA for Zen CPU's.
Regards, Ramesh
-----Original Message----- From: Alex Deucher alexdeucher@gmail.com Sent: Wednesday, August 11, 2021 4:07 PM To: Kuehling, Felix Felix.Kuehling@amd.com Cc: Errabolu, Ramesh Ramesh.Errabolu@amd.com; amd-gfx list amd-gfx@lists.freedesktop.org; Maling list - DRI developers dri-devel@lists.freedesktop.org; Bjorn Helgaas bhelgaas@google.com; Linux PCI linux-pci@vger.kernel.org; LKML linux-kernel@vger.kernel.org Subject: Re: [PATCH] Whitelist AMD host bridge device(s) to enable P2P DMA
[CAUTION: External Email]
On Wed, Aug 11, 2021 at 4:50 PM Felix Kuehling felix.kuehling@amd.com wrote:
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.
We don't need to keep adding AMD root complexes. You must be using an older kernel or something. All root complexes on all Zen platforms support P2P DMA. See:
commit dea286bb71baded7d2fb4f090e3b9fd2c1ccac58 Author: Logan Gunthorpe logang@deltatee.com Date: Wed Jul 29 17:18:44 2020 -0600
PCI/P2PDMA: Allow P2PDMA on AMD Zen and newer CPUs
Allow P2PDMA if the CPU vendor is AMD and family is 0x17 (Zen) or greater.
[bhelgaas: commit log, simplify #if/#else/#endif] Link: https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Flore.kerne... Signed-off-by: Logan Gunthorpe logang@deltatee.com Signed-off-by: Bjorn Helgaas bhelgaas@google.com Reviewed-by: Alex Deucher alexander.deucher@amd.com Cc: Christian König christian.koenig@amd.com Cc: Huang Rui ray.huang@amd.com
Alex
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
dri-devel@lists.freedesktop.org
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Alex Deucher -
Errabolu, Ramesh -
Felix Kuehling -
Ramesh Errabolu