On 2024-08-14 11:17, Alex Deucher wrote:
On Wed, Aug 14, 2024 at 5:15 AM Rahul Jain <Rahul.Jain@xxxxxxx> wrote:
when trying to enable p2p the amdgpu_device_is_peer_accessible()
checks the condition where address_mask overlaps the aper_base
and hence returns 0, due to which the p2p disables for this platform
IOMMU should remap the BAR addresses so the device can access
them. Hence check if peer_adev is remapping DMA
v3:
- remove iommu_remap variable
v2: (Alex)
- Fix as per review comments
- add new function amdgpu_device_check_iommu_remap to check if iommu
remap
Signed-off-by: Rahul Jain <Rahul.Jain@xxxxxxx>
---
drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 46 +++++++++++++++++++---
1 file changed, 40 insertions(+), 6 deletions(-)
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
index a6b8d0ba4758..040c75c491cd 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
@@ -3952,6 +3952,25 @@ static void amdgpu_device_check_iommu_direct_map(struct amdgpu_device *adev)
adev->ram_is_direct_mapped = true;
}
+/**
+ * amdgpu_device_check_iommu_remap - check if iommu remaped BAR
change this to:
Check if DMA remapping is enabled.
since it's not just the BAR, all system address space accesses will be remapped.
+ *
+ * @adev: amdgpu_device pointer
+ *
+ * return if IOMMU remapping bar address
+ */
+static bool amdgpu_device_check_iommu_remap(struct amdgpu_device *adev)
+{
+ struct iommu_domain *domain;
+
+ domain = iommu_get_domain_for_dev(adev->dev);
+ if (domain && (domain->type == IOMMU_DOMAIN_DMA ||
+ domain->type == IOMMU_DOMAIN_DMA_FQ))
+ return true;
+
+ return false;
+}
+
static const struct attribute *amdgpu_dev_attributes[] = {
&dev_attr_pcie_replay_count.attr,
NULL
@@ -6127,6 +6146,8 @@ bool amdgpu_device_is_peer_accessible(struct amdgpu_device *adev,
struct amdgpu_device *peer_adev)
{
#ifdef CONFIG_HSA_AMD_P2P
+ bool peer_remap = amdgpu_device_check_iommu_remap(peer_adev);
+
uint64_t address_mask = peer_adev->dev->dma_mask ?
~*peer_adev->dev->dma_mask : ~((1ULL << 32) - 1);
resource_size_t aper_limit =
@@ -6135,13 +6156,26 @@ bool amdgpu_device_is_peer_accessible(struct amdgpu_device *adev,
!adev->gmc.xgmi.connected_to_cpu &&
!(pci_p2pdma_distance(adev->pdev, peer_adev->dev, false) < 0);
- return pcie_p2p && p2p_access && (adev->gmc.visible_vram_size &&
- adev->gmc.real_vram_size == adev->gmc.visible_vram_size &&
- !(adev->gmc.aper_base & address_mask ||
- aper_limit & address_mask));
-#else
- return false;
+ if (peer_remap)
+ /**
These don't need to be kerneldoc comments. Replace /** with /*
+ * IOMMU is remapping DMA for peer_adev so all accesses
+ * should be within peer_adev's DMA mask
+ */
+ return pcie_p2p && p2p_access &&
+ (adev->gmc.visible_vram_size &&
+ adev->gmc.real_vram_size == adev->gmc.visible_vram_size);
+ else
+ /**
Same here.
With those fixed, it looks good to me, but it would be good if Ramesh
took a look as well as he wrote this code originally.
Looks reasonable to me. But it could be refactored to avoid duplicating
a bunch of the condition. Maybe something like:
bool is_large_bar = adev->gmc.visible_vram_size &&
adev->gmc.real_vram_size == adev->gmc.visible_vram_size;
bool p2p_access =
!adev->gmc.xgmi.connected_to_cpu &&
!(pci_p2pdma_distance(adev->pdev, peer_adev->dev, false) < 0);
bool p2p_addressable = amdgpu_device_check_iommu_remap(peer_adev);
if (!p2p_addressable) {
uint64_t address_mask = peer_adev->dev->dma_mask ?
~*peer_adev->dev->dma_mask : ~((1ULL << 32) - 1);
resource_size_t aper_limit =
adev->gmc.aper_base + adev->gmc.aper_size - 1;
peer_addressable = !(adev->gmc.aper_base & address_mask ||
aper_limit & address_mask);
}
return is_large_bar && p2p_access && p2p_addressable;
Regards,
Felix
Alex
+ * No IOMMU remapping so make sure the adev's aperture
+ * fits into peer_adev's dma mask
+ */
+ return pcie_p2p && p2p_access &&
+ (adev->gmc.visible_vram_size &&
+ adev->gmc.real_vram_size == adev->gmc.visible_vram_size &&
+ !(adev->gmc.aper_base & address_mask ||
+ aper_limit & address_mask));
#endif
+ return false;
}
int amdgpu_device_baco_enter(struct drm_device *dev)
--
2.34.1
