[PATCH 2/3] drm/amdgpu: Add peer-to-peer support among PCIe connected AMD GPUs
Ramesh Errabolu
Ramesh.Errabolu at amd.com
Mon Jun 6 18:07:42 UTC 2022
Add support for peer-to-peer communication among AMD GPUs over PCIe
bus. Support REQUIRES enablement of config HSA_AMD_P2P.
Signed-off-by: Ramesh Errabolu <Ramesh.Errabolu at amd.com>
---
drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd.h | 1 +
.../gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c | 300 ++++++++++++++----
drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 33 ++
drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c | 8 +
4 files changed, 280 insertions(+), 62 deletions(-)
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd.h
index f8b9f27adcf5..5c00ea1df21c 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd.h
@@ -48,6 +48,7 @@ enum kfd_mem_attachment_type {
KFD_MEM_ATT_SHARED, /* Share kgd_mem->bo or another attachment's */
KFD_MEM_ATT_USERPTR, /* SG bo to DMA map pages from a userptr bo */
KFD_MEM_ATT_DMABUF, /* DMAbuf to DMA map TTM BOs */
+ KFD_MEM_ATT_SG /* Tag to DMA map SG BOs */
};
struct kfd_mem_attachment {
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
index 054e4a76ae2e..ce012a148ed7 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
@@ -241,6 +241,42 @@ void amdgpu_amdkfd_release_notify(struct amdgpu_bo *bo)
kfree(bo->kfd_bo);
}
+/**
+ * @create_dmamap_sg_bo: Creates a amdgpu_bo object to reflect information
+ * about USERPTR or DOOREBELL or MMIO BO.
+ * @adev: Device for which dmamap BO is being created
+ * @mem: BO of peer device that is being DMA mapped. Provides parameters
+ * in building the dmamap BO
+ * @bo_out: Output parameter updated with handle of dmamap BO
+ */
+static int
+create_dmamap_sg_bo(struct amdgpu_device *adev,
+ struct kgd_mem *mem, struct amdgpu_bo **bo_out)
+{
+ struct drm_gem_object *gem_obj;
+ int ret, align;
+
+ ret = amdgpu_bo_reserve(mem->bo, false);
+ if (ret)
+ return ret;
+
+ align = 1;
+ ret = amdgpu_gem_object_create(adev, mem->bo->tbo.base.size, align,
+ AMDGPU_GEM_DOMAIN_CPU, AMDGPU_GEM_CREATE_PREEMPTIBLE,
+ ttm_bo_type_sg, mem->bo->tbo.base.resv, &gem_obj);
+
+ amdgpu_bo_unreserve(mem->bo);
+
+ if (ret) {
+ pr_err("Error in creating DMA mappable SG BO on domain: %d\n", ret);
+ return -EINVAL;
+ }
+
+ *bo_out = gem_to_amdgpu_bo(gem_obj);
+ (*bo_out)->parent = amdgpu_bo_ref(mem->bo);
+ return ret;
+}
+
/* amdgpu_amdkfd_remove_eviction_fence - Removes eviction fence from BO's
* reservation object.
*
@@ -481,6 +517,38 @@ static uint64_t get_pte_flags(struct amdgpu_device *adev, struct kgd_mem *mem)
return pte_flags;
}
+/**
+ * create_sg_table() - Create an sg_table for a contiguous DMA addr range
+ * @addr: The starting address to point to
+ * @size: Size of memory area in bytes being pointed to
+ *
+ * Allocates an instance of sg_table and initializes it to point to memory
+ * area specified by input parameters. The address used to build is assumed
+ * to be DMA mapped, if needed.
+ *
+ * DOORBELL or MMIO BOs use only one scatterlist node in their sg_table
+ * because they are physically contiguous.
+ *
+ * Return: Initialized instance of SG Table or NULL
+ */
+static struct sg_table *create_sg_table(uint64_t addr, uint32_t size)
+{
+ struct sg_table *sg = kmalloc(sizeof(*sg), GFP_KERNEL);
+
+ if (!sg)
+ return NULL;
+ if (sg_alloc_table(sg, 1, GFP_KERNEL)) {
+ kfree(sg);
+ return NULL;
+ }
+ sg_dma_address(sg->sgl) = addr;
+ sg->sgl->length = size;
+#ifdef CONFIG_NEED_SG_DMA_LENGTH
+ sg->sgl->dma_length = size;
+#endif
+ return sg;
+}
+
static int
kfd_mem_dmamap_userptr(struct kgd_mem *mem,
struct kfd_mem_attachment *attachment)
@@ -545,6 +613,87 @@ kfd_mem_dmamap_dmabuf(struct kfd_mem_attachment *attachment)
return ttm_bo_validate(&bo->tbo, &bo->placement, &ctx);
}
+/**
+ * kfd_mem_dmamap_sg_bo() - Create DMA mapped sg_table to access DOORBELL or MMIO BO
+ * @mem: SG BO of the DOORBELL or MMIO resource on the owning device
+ * @attachment: Virtual address attachment of the BO on accessing device
+ *
+ * An access request from the device that owns DOORBELL does not require DMA mapping.
+ * This is because the request doesn't go through PCIe root complex i.e. it instead
+ * loops back. The need to DMA map arises only when accessing peer device's DOORBELL
+ *
+ * In contrast, all access requests for MMIO need to be DMA mapped without regard to
+ * device ownership. This is because access requests for MMIO go through PCIe root
+ * complex.
+ *
+ * This is accomplished in two steps:
+ * - Obtain DMA mapped address of DOORBELL or MMIO memory that could be used
+ * in updating requesting device's page table
+ * - Signal TTM to mark memory pointed to by requesting device's BO as GPU
+ * accessible. This allows an update of requesting device's page table
+ * with entries associated with DOOREBELL or MMIO memory
+ *
+ * This method is invoked in the following contexts:
+ * - Mapping of DOORBELL or MMIO BO of same or peer device
+ * - Validating an evicted DOOREBELL or MMIO BO on device seeking access
+ *
+ * Return: ZERO if successful, NON-ZERO otherwise
+ */
+static int
+kfd_mem_dmamap_sg_bo(struct kgd_mem *mem,
+ struct kfd_mem_attachment *attachment)
+{
+ struct ttm_operation_ctx ctx = {.interruptible = true};
+ struct amdgpu_bo *bo = attachment->bo_va->base.bo;
+ struct amdgpu_device *adev = attachment->adev;
+ struct ttm_tt *ttm = bo->tbo.ttm;
+ enum dma_data_direction dir;
+ dma_addr_t dma_addr;
+ bool mmio;
+ int ret;
+
+ /* Expect SG Table of dmapmap BO to be NULL */
+ mmio = (mem->alloc_flags & KFD_IOC_ALLOC_MEM_FLAGS_MMIO_REMAP);
+ if (unlikely(ttm->sg)) {
+ pr_err("SG Table of %d BO for peer device is UNEXPECTEDLY NON-NULL", mmio);
+ return -EINVAL;
+ }
+
+ dir = mem->alloc_flags & KFD_IOC_ALLOC_MEM_FLAGS_WRITABLE ?
+ DMA_BIDIRECTIONAL : DMA_TO_DEVICE;
+ dma_addr = mem->bo->tbo.sg->sgl->dma_address;
+ pr_debug("%d BO size: %d\n", mmio, mem->bo->tbo.sg->sgl->length);
+ pr_debug("%d BO address before DMA mapping: %llx\n", mmio, dma_addr);
+ dma_addr = dma_map_resource(adev->dev, dma_addr,
+ mem->bo->tbo.sg->sgl->length, dir, DMA_ATTR_SKIP_CPU_SYNC);
+ ret = dma_mapping_error(adev->dev, dma_addr);
+ if (unlikely(ret))
+ return ret;
+ pr_debug("%d BO address after DMA mapping: %llx\n", mmio, dma_addr);
+
+ ttm->sg = create_sg_table(dma_addr, mem->bo->tbo.sg->sgl->length);
+ if (unlikely(!ttm->sg)) {
+ ret = -ENOMEM;
+ goto unmap_sg;
+ }
+
+ amdgpu_bo_placement_from_domain(bo, AMDGPU_GEM_DOMAIN_GTT);
+ ret = ttm_bo_validate(&bo->tbo, &bo->placement, &ctx);
+ if (unlikely(ret))
+ goto free_sg;
+
+ return ret;
+
+free_sg:
+ sg_free_table(ttm->sg);
+ kfree(ttm->sg);
+ ttm->sg = NULL;
+unmap_sg:
+ dma_unmap_resource(adev->dev, dma_addr, mem->bo->tbo.sg->sgl->length,
+ dir, DMA_ATTR_SKIP_CPU_SYNC);
+ return ret;
+}
+
static int
kfd_mem_dmamap_attachment(struct kgd_mem *mem,
struct kfd_mem_attachment *attachment)
@@ -556,6 +705,8 @@ kfd_mem_dmamap_attachment(struct kgd_mem *mem,
return kfd_mem_dmamap_userptr(mem, attachment);
case KFD_MEM_ATT_DMABUF:
return kfd_mem_dmamap_dmabuf(attachment);
+ case KFD_MEM_ATT_SG:
+ return kfd_mem_dmamap_sg_bo(mem, attachment);
default:
WARN_ON_ONCE(1);
}
@@ -596,6 +747,50 @@ kfd_mem_dmaunmap_dmabuf(struct kfd_mem_attachment *attachment)
ttm_bo_validate(&bo->tbo, &bo->placement, &ctx);
}
+/**
+ * kfd_mem_dmaunmap_sg_bo() - Free DMA mapped sg_table of DOORBELL or MMIO BO
+ * @mem: SG BO of the DOORBELL or MMIO resource on the owning device
+ * @attachment: Virtual address attachment of the BO on accessing device
+ *
+ * The method performs following steps:
+ * - Signal TTM to mark memory pointed to by BO as GPU inaccessible
+ * - Free SG Table that is used to encapsulate DMA mapped memory of
+ * peer device's DOORBELL or MMIO memory
+ *
+ * This method is invoked in the following contexts:
+ * UNMapping of DOORBELL or MMIO BO on a device having access to its memory
+ * Eviction of DOOREBELL or MMIO BO on device having access to its memory
+ *
+ * Return: void
+ */
+static void
+kfd_mem_dmaunmap_sg_bo(struct kgd_mem *mem,
+ struct kfd_mem_attachment *attachment)
+{
+ struct ttm_operation_ctx ctx = {.interruptible = true};
+ struct amdgpu_bo *bo = attachment->bo_va->base.bo;
+ struct amdgpu_device *adev = attachment->adev;
+ struct ttm_tt *ttm = bo->tbo.ttm;
+ enum dma_data_direction dir;
+
+ if (unlikely(!ttm->sg)) {
+ pr_err("SG Table of BO is UNEXPECTEDLY NULL");
+ return;
+ }
+
+ amdgpu_bo_placement_from_domain(bo, AMDGPU_GEM_DOMAIN_CPU);
+ ttm_bo_validate(&bo->tbo, &bo->placement, &ctx);
+
+ dir = mem->alloc_flags & KFD_IOC_ALLOC_MEM_FLAGS_WRITABLE ?
+ DMA_BIDIRECTIONAL : DMA_TO_DEVICE;
+ dma_unmap_resource(adev->dev, ttm->sg->sgl->dma_address,
+ ttm->sg->sgl->length, dir, DMA_ATTR_SKIP_CPU_SYNC);
+ sg_free_table(ttm->sg);
+ kfree(ttm->sg);
+ ttm->sg = NULL;
+ bo->tbo.sg = NULL;
+}
+
static void
kfd_mem_dmaunmap_attachment(struct kgd_mem *mem,
struct kfd_mem_attachment *attachment)
@@ -609,38 +804,14 @@ kfd_mem_dmaunmap_attachment(struct kgd_mem *mem,
case KFD_MEM_ATT_DMABUF:
kfd_mem_dmaunmap_dmabuf(attachment);
break;
+ case KFD_MEM_ATT_SG:
+ kfd_mem_dmaunmap_sg_bo(mem, attachment);
+ break;
default:
WARN_ON_ONCE(1);
}
}
-static int
-kfd_mem_attach_userptr(struct amdgpu_device *adev, struct kgd_mem *mem,
- struct amdgpu_bo **bo)
-{
- unsigned long bo_size = mem->bo->tbo.base.size;
- struct drm_gem_object *gobj;
- int ret;
-
- ret = amdgpu_bo_reserve(mem->bo, false);
- if (ret)
- return ret;
-
- ret = amdgpu_gem_object_create(adev, bo_size, 1,
- AMDGPU_GEM_DOMAIN_CPU,
- AMDGPU_GEM_CREATE_PREEMPTIBLE,
- ttm_bo_type_sg, mem->bo->tbo.base.resv,
- &gobj);
- amdgpu_bo_unreserve(mem->bo);
- if (ret)
- return ret;
-
- *bo = gem_to_amdgpu_bo(gobj);
- (*bo)->parent = amdgpu_bo_ref(mem->bo);
-
- return 0;
-}
-
static int
kfd_mem_attach_dmabuf(struct amdgpu_device *adev, struct kgd_mem *mem,
struct amdgpu_bo **bo)
@@ -691,6 +862,7 @@ static int kfd_mem_attach(struct amdgpu_device *adev, struct kgd_mem *mem,
uint64_t va = mem->va;
struct kfd_mem_attachment *attachment[2] = {NULL, NULL};
struct amdgpu_bo *bo[2] = {NULL, NULL};
+ bool same_hive = false;
int i, ret;
if (!va) {
@@ -698,6 +870,24 @@ static int kfd_mem_attach(struct amdgpu_device *adev, struct kgd_mem *mem,
return -EINVAL;
}
+ /* Determine access to VRAM, MMIO and DOORBELL BOs of peer devices
+ *
+ * The access path of MMIO and DOORBELL BOs of is always over PCIe.
+ * In contrast the access path of VRAM BOs depens upon the type of
+ * link that connects the peer device. Access over PCIe is allowed
+ * if peer device has large BAR. In contrast, access over xGMI is
+ * allowed for both small and large BAR configurations of peer device
+ */
+ if ((adev != bo_adev) &&
+ ((mem->domain == AMDGPU_GEM_DOMAIN_VRAM) ||
+ (mem->alloc_flags & KFD_IOC_ALLOC_MEM_FLAGS_DOORBELL) ||
+ (mem->alloc_flags & KFD_IOC_ALLOC_MEM_FLAGS_MMIO_REMAP))) {
+ if (mem->domain == AMDGPU_GEM_DOMAIN_VRAM)
+ same_hive = amdgpu_xgmi_same_hive(adev, bo_adev);
+ if (!same_hive && !amdgpu_device_is_peer_accessible(bo_adev, adev))
+ return -EINVAL;
+ }
+
for (i = 0; i <= is_aql; i++) {
attachment[i] = kzalloc(sizeof(*attachment[i]), GFP_KERNEL);
if (unlikely(!attachment[i])) {
@@ -708,9 +898,9 @@ static int kfd_mem_attach(struct amdgpu_device *adev, struct kgd_mem *mem,
pr_debug("\t add VA 0x%llx - 0x%llx to vm %p\n", va,
va + bo_size, vm);
- if (adev == bo_adev ||
- (amdgpu_ttm_tt_get_usermm(mem->bo->tbo.ttm) && adev->ram_is_direct_mapped) ||
- (mem->domain == AMDGPU_GEM_DOMAIN_VRAM && amdgpu_xgmi_same_hive(adev, bo_adev))) {
+ if ((adev == bo_adev && !(mem->alloc_flags & KFD_IOC_ALLOC_MEM_FLAGS_MMIO_REMAP)) ||
+ (amdgpu_ttm_tt_get_usermm(mem->bo->tbo.ttm) && adev->ram_is_direct_mapped) ||
+ same_hive) {
/* Mappings on the local GPU, or VRAM mappings in the
* local hive, or userptr mapping IOMMU direct map mode
* share the original BO
@@ -726,26 +916,30 @@ static int kfd_mem_attach(struct amdgpu_device *adev, struct kgd_mem *mem,
} else if (amdgpu_ttm_tt_get_usermm(mem->bo->tbo.ttm)) {
/* Create an SG BO to DMA-map userptrs on other GPUs */
attachment[i]->type = KFD_MEM_ATT_USERPTR;
- ret = kfd_mem_attach_userptr(adev, mem, &bo[i]);
+ ret = create_dmamap_sg_bo(adev, mem, &bo[i]);
if (ret)
goto unwind;
- } else if (mem->domain == AMDGPU_GEM_DOMAIN_GTT &&
- mem->bo->tbo.type != ttm_bo_type_sg) {
- /* GTT BOs use DMA-mapping ability of dynamic-attach
- * DMA bufs. TODO: The same should work for VRAM on
- * large-BAR GPUs.
- */
+ /* Handle DOORBELL BOs of peer devices and MMIO BOs of local and peer devices */
+ } else if (mem->bo->tbo.type == ttm_bo_type_sg) {
+ WARN_ONCE(!(mem->alloc_flags & KFD_IOC_ALLOC_MEM_FLAGS_DOORBELL ||
+ mem->alloc_flags & KFD_IOC_ALLOC_MEM_FLAGS_MMIO_REMAP),
+ "Handing invalid SG BO in ATTACH request");
+ attachment[i]->type = KFD_MEM_ATT_SG;
+ ret = create_dmamap_sg_bo(adev, mem, &bo[i]);
+ if (ret)
+ goto unwind;
+ /* Enable acces to GTT and VRAM BOs of peer devices */
+ } else if (mem->domain == AMDGPU_GEM_DOMAIN_GTT ||
+ mem->domain == AMDGPU_GEM_DOMAIN_VRAM) {
attachment[i]->type = KFD_MEM_ATT_DMABUF;
ret = kfd_mem_attach_dmabuf(adev, mem, &bo[i]);
if (ret)
goto unwind;
+ pr_debug("Employ DMABUF mechanim to enable peer GPU access\n");
} else {
- /* FIXME: Need to DMA-map other BO types:
- * large-BAR VRAM, doorbells, MMIO remap
- */
- attachment[i]->type = KFD_MEM_ATT_SHARED;
- bo[i] = mem->bo;
- drm_gem_object_get(&bo[i]->tbo.base);
+ WARN_ONCE(true, "Handling invalid ATTACH request");
+ ret = -EINVAL;
+ goto unwind;
}
/* Add BO to VM internal data structures */
@@ -1146,24 +1340,6 @@ static int map_bo_to_gpuvm(struct kgd_mem *mem,
return ret;
}
-static struct sg_table *create_doorbell_sg(uint64_t addr, uint32_t size)
-{
- struct sg_table *sg = kmalloc(sizeof(*sg), GFP_KERNEL);
-
- if (!sg)
- return NULL;
- if (sg_alloc_table(sg, 1, GFP_KERNEL)) {
- kfree(sg);
- return NULL;
- }
- sg->sgl->dma_address = addr;
- sg->sgl->length = size;
-#ifdef CONFIG_NEED_SG_DMA_LENGTH
- sg->sgl->dma_length = size;
-#endif
- return sg;
-}
-
static int process_validate_vms(struct amdkfd_process_info *process_info)
{
struct amdgpu_vm *peer_vm;
@@ -1532,7 +1708,7 @@ int amdgpu_amdkfd_gpuvm_alloc_memory_of_gpu(
bo_type = ttm_bo_type_sg;
if (size > UINT_MAX)
return -EINVAL;
- sg = create_doorbell_sg(*offset, size);
+ sg = create_sg_table(*offset, size);
if (!sg)
return -ENOMEM;
} else {
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
index be0baacc5942..8e88e7c88d26 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
@@ -34,6 +34,7 @@
#include <linux/pci.h>
#include <linux/devcoredump.h>
#include <generated/utsrelease.h>
+#include <linux/pci-p2pdma.h>
#include <drm/drm_atomic_helper.h>
#include <drm/drm_probe_helper.h>
@@ -129,6 +130,8 @@ const char *amdgpu_asic_name[] = {
"LAST",
};
+extern bool pcie_p2p;
+
/**
* DOC: pcie_replay_count
*
@@ -5498,6 +5501,36 @@ static void amdgpu_device_get_pcie_info(struct amdgpu_device *adev)
}
}
+/**
+ * amdgpu_device_is_peer_accessible - Check peer access through PCIe BAR
+ *
+ * @adev: amdgpu_device pointer
+ * @peer_adev: amdgpu_device pointer for peer device trying to access @adev
+ *
+ * Return true if @peer_adev can access (DMA) @adev through the PCIe
+ * BAR, i.e. @adev is "large BAR" and the BAR matches the DMA mask of
+ * @peer_adev.
+ */
+bool amdgpu_device_is_peer_accessible(struct amdgpu_device *adev,
+ struct amdgpu_device *peer_adev)
+{
+#ifdef CONFIG_HSA_AMD_P2P
+ 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;
+ bool p2p_access = !(pci_p2pdma_distance_many(adev->pdev,
+ &peer_adev->dev, 1, true) < 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;
+#endif
+}
+
int amdgpu_device_baco_enter(struct drm_device *dev)
{
struct amdgpu_device *adev = drm_to_adev(dev);
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
index bed4ed88951f..d1c82a9e8569 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
@@ -802,6 +802,14 @@ MODULE_PARM_DESC(no_queue_eviction_on_vm_fault, "No queue eviction on VM fault (
module_param_named(no_queue_eviction_on_vm_fault, amdgpu_no_queue_eviction_on_vm_fault, int, 0444);
#endif
+/**
+ * DOC: pcie_p2p (bool)
+ * Enable PCIe P2P (requires large-BAR). Default value: true (on)
+ */
+bool pcie_p2p = true;
+module_param(pcie_p2p, bool, 0444);
+MODULE_PARM_DESC(pcie_p2p, "Enable PCIe P2P (requires large-BAR). (N = off, Y = on(default))");
+
/**
* DOC: dcfeaturemask (uint)
* Override display features enabled. See enum DC_FEATURE_MASK in drivers/gpu/drm/amd/include/amd_shared.h.
--
2.35.1
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