Re: [PATCH 1/3] amd/amdkfd: Add granularity bitmap mapped to gpu flag

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On 9/29/2023 9:11 AM, Philip Yang wrote:
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Replace prange->mapped_to_gpu with prange->bitmap_mapped[], which is
based on prange granularity, updated when map to GPUS or unmap from
GPUs, to optimize multiple GPU map, unmap and retry fault recover.

svm_range_is_mapped is false only if no parital range mapping on any
GPUs.

Split the bitmap_mapped when unmap from cpu to split the prange.

Signed-off-by: Philip Yang <Philip.Yang@xxxxxxx>
---
  drivers/gpu/drm/amd/amdkfd/kfd_svm.c | 218 ++++++++++++++++++++++-----
  drivers/gpu/drm/amd/amdkfd/kfd_svm.h |   4 +-
  2 files changed, 184 insertions(+), 38 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
index 040dc32ad475..626e0dd4ec79 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
@@ -292,12 +292,12 @@ static void svm_range_free(struct svm_range *prange, bool do_unmap)
                                         KFD_IOC_ALLOC_MEM_FLAGS_USERPTR, 0);
         }

-       /* free dma_addr array for each gpu */
+       /* free dma_addr array, bitmap_mapped for each gpu */
         for (gpuidx = 0; gpuidx < MAX_GPU_INSTANCE; gpuidx++) {
-               if (prange->dma_addr[gpuidx]) {
+               if (prange->dma_addr[gpuidx])
                         kvfree(prange->dma_addr[gpuidx]);
-                               prange->dma_addr[gpuidx] = NULL;
-               }
+               if (prange->bitmap_mapped[gpuidx])
+                       bitmap_free(prange->bitmap_mapped[gpuidx]);
         }

         mutex_destroy(&prange->lock);
@@ -323,19 +323,38 @@ svm_range *svm_range_new(struct svm_range_list *svms, uint64_t start,
         uint64_t size = last - start + 1;
         struct svm_range *prange;
         struct kfd_process *p;
-
-       prange = kzalloc(sizeof(*prange), GFP_KERNEL);
-       if (!prange)
-               return NULL;
+       unsigned int nbits;
+       uint32_t gpuidx;

         p = container_of(svms, struct kfd_process, svms);
         if (!p->xnack_enabled && update_mem_usage &&
             amdgpu_amdkfd_reserve_mem_limit(NULL, size << PAGE_SHIFT,
                                     KFD_IOC_ALLOC_MEM_FLAGS_USERPTR, 0)) {
                 pr_info("SVM mapping failed, exceeds resident system memory limit\n");
-               kfree(prange);
                 return NULL;
         }
+
+       prange = kzalloc(sizeof(*prange), GFP_KERNEL);
+       if (!prange)
+               return NULL;
+
+       svm_range_set_default_attributes(&prange->preferred_loc,
+                                        &prange->prefetch_loc,
+                                        &prange->granularity, &prange->flags);
+
+       nbits = svm_range_mapped_nbits(size, prange->granularity);
+       pr_debug("prange 0x%p [0x%llx 0x%llx] bitmap_mapped nbits %d\n", prange,
+                start, last, nbits);
+       for_each_set_bit(gpuidx, p->svms.bitmap_supported, p->n_pdds) {
+               prange->bitmap_mapped[gpuidx] = bitmap_zalloc(nbits, GFP_KERNEL);
+               if (!prange->bitmap_mapped[gpuidx]) {
+                       while (gpuidx--)
+                               bitmap_free(prange->bitmap_mapped[gpuidx]);
+                       kfree(prange);
+                       return NULL;
+               }
+       }
+
         prange->npages = size;
         prange->svms = svms;
         prange->start = start;
@@ -354,10 +373,6 @@ svm_range *svm_range_new(struct svm_range_list *svms, uint64_t start,
                 bitmap_copy(prange->bitmap_access, svms->bitmap_supported,
                             MAX_GPU_INSTANCE);

-       svm_range_set_default_attributes(&prange->preferred_loc,
-                                        &prange->prefetch_loc,
-                                        &prange->granularity, &prange->flags);
-
         pr_debug("svms 0x%p [0x%llx 0x%llx]\n", svms, start, last);

         return prange;
@@ -972,6 +987,48 @@ svm_range_split_nodes(struct svm_range *new, struct svm_range *old,
         return 0;
  }

+static int
+svm_range_split_bitmap_mapped(struct svm_range *new, struct svm_range *old,
+                             uint64_t start, uint64_t last)
+{
+       struct kfd_process *p = container_of(new->svms, struct kfd_process, svms);
+       unsigned int nbits, old_nbits, old_nbits2;
+       unsigned long *bits;
+       uint32_t gpuidx;
+
+       nbits = svm_range_mapped_nbits(new->npages, new->granularity);
+       old_nbits = svm_range_mapped_nbits(old->npages, old->granularity);
+       old_nbits2 = svm_range_mapped_nbits(last - start + 1, old->granularity);
+
+       pr_debug("old 0x%p [0x%lx 0x%lx] => [0x%llx 0x%llx] nbits %d => %d\n",
+                old, old->start, old->last, start, last, old_nbits, old_nbits2);
+       pr_debug("new 0x%p [0x%lx 0x%lx] nbits %d\n", new, new->start, new->last,
+                nbits);
+
+       for_each_set_bit(gpuidx, p->svms.bitmap_supported, p->n_pdds) {
+               bits = bitmap_alloc(old_nbits2, GFP_KERNEL);
+               if (!bits)
+                       return -ENOMEM;
+
+               if (start == old->start) {
+                       bitmap_shift_right(new->bitmap_mapped[gpuidx],
+                                          old->bitmap_mapped[gpuidx],
+                                          old_nbits2, old_nbits);
+                       bitmap_shift_right(bits, old->bitmap_mapped[gpuidx], 0,
+                                          old_nbits2);
+               } else {
+                       bitmap_copy(new->bitmap_mapped[gpuidx],
+                                   old->bitmap_mapped[gpuidx], nbits);
+                       bitmap_shift_right(bits, old->bitmap_mapped[gpuidx],
+                                          nbits, old_nbits);
+               }
+               bitmap_free(old->bitmap_mapped[gpuidx]);
+               old->bitmap_mapped[gpuidx] = bits;
+       }
+
+       return 0;
+}
+
  /**
   * svm_range_split_adjust - split range and adjust
   *
@@ -1012,6 +1069,10 @@ svm_range_split_adjust(struct svm_range *new, struct svm_range *old,
                         return r;
         }

+       r = svm_range_split_bitmap_mapped(new, old, start, last);
+       if (r)
+               return r;
+
         old->npages = last - start + 1;
         old->start = start;
         old->last = last;
@@ -1020,7 +1081,6 @@ svm_range_split_adjust(struct svm_range *new, struct svm_range *old,
         new->prefetch_loc = old->prefetch_loc;
         new->actual_loc = old->actual_loc;
         new->granularity = old->granularity;
-       new->mapped_to_gpu = old->mapped_to_gpu;
         bitmap_copy(new->bitmap_access, old->bitmap_access, MAX_GPU_INSTANCE);
         bitmap_copy(new->bitmap_aip, old->bitmap_aip, MAX_GPU_INSTANCE);

@@ -1310,6 +1370,84 @@ svm_range_unmap_from_gpu(struct amdgpu_device *adev, struct amdgpu_vm *vm,
                                       fence);
  }

+/**
+ * svm_range_partial_mapped_dev - check if prange mapped on the specific gpu
+ *
+ * @gpuidx: the gpu to check
+ * @prange: prange to check
+ * @start: the start address in pages
+ * @last: the last address in pages
+ *
+ * Return:
+ * true: if any partial range mapped on gpu based on granularity boundary
+ * false: if the entire range not mapped
+ */
+static bool
+svm_range_partial_mapped_dev(uint32_t gpuidx, struct svm_range *prange,
+                            unsigned long start, unsigned long last)
+{
+       unsigned long index, off;
+       bool mapped = false;
+
+       start = max(start, prange->start);
+       last = min(last, prange->last);
+       if (last < start)
+               goto out;
+
+       for (off = start; off <= last; off += (1UL << prange->granularity)) {
+               index = (off - prange->start) >> prange->granularity;
+               if (test_bit(index, prange->bitmap_mapped[gpuidx])) {
+                       mapped = true;
+                       break;
+               }
+       }
+out:
+       pr_debug("prange 0x%p [0x%lx 0x%lx] mapped %d on gpu %d\n", prange,
+                start, last, mapped, gpuidx);
+       return mapped;
+}
+
+static bool
+svm_range_partial_mapped(struct svm_range *prange, unsigned long start,
+                        unsigned long last)
+{
+       struct kfd_process *p = container_of(prange->svms, struct kfd_process, svms);
+       struct svm_range *pchild;
+       uint32_t gpuidx;
+
+       for_each_set_bit(gpuidx, p->svms.bitmap_supported, p->n_pdds) {
+               list_for_each_entry(pchild, &prange->child_list, child_list) {
+                       if (svm_range_partial_mapped_dev(gpuidx, pchild, start, last))
+                               return true;
+               }
+
+               if (svm_range_partial_mapped_dev(gpuidx, prange, start, last))
+                       return true;
+       }
+       return false;
+}
+
+static bool svm_range_is_mapped(struct svm_range *prange)
+{
+       return svm_range_partial_mapped(prange, prange->start, prange->last);
+}
+
I think svm_range_is_mapped actually means if there is any prange->granularity range inside prange is mapped to any gpu, not prange got mapped. The name is confusion.
+static void
+svm_range_update_mapped(uint32_t gpuidx, struct svm_range *prange,
+                       unsigned long start, unsigned long last, bool mapped)
+{
+       unsigned long index, nbits;
+
+       index = (start - prange->start) >> prange->granularity;
+       nbits = svm_range_mapped_nbits(last - start + 1, prange->granularity);
+       if (mapped)
+               bitmap_set(prange->bitmap_mapped[gpuidx], index, nbits);
+       else
+               bitmap_clear(prange->bitmap_mapped[gpuidx], index, nbits);
+       pr_debug("prange 0x%p [0x%lx 0x%lx] update mapped %d nbits %ld gpu %d\n",
+                prange, start, last, mapped, nbits, gpuidx);
+}
+
  static int
  svm_range_unmap_from_gpus(struct svm_range *prange, unsigned long start,
                           unsigned long last, uint32_t trigger)
@@ -1321,29 +1459,28 @@ svm_range_unmap_from_gpus(struct svm_range *prange, unsigned long start,
         uint32_t gpuidx;
         int r = 0;

-       if (!prange->mapped_to_gpu) {
-               pr_debug("prange 0x%p [0x%lx 0x%lx] not mapped to GPU\n",
-                        prange, prange->start, prange->last);
-               return 0;
-       }
-
-       if (prange->start == start && prange->last == last) {
-               pr_debug("unmap svms 0x%p prange 0x%p\n", prange->svms, prange);
-               prange->mapped_to_gpu = false;
-       }
-
         bitmap_or(bitmap, prange->bitmap_access, prange->bitmap_aip,
                   MAX_GPU_INSTANCE);
         p = container_of(prange->svms, struct kfd_process, svms);

         for_each_set_bit(gpuidx, bitmap, MAX_GPU_INSTANCE) {
-               pr_debug("unmap from gpu idx 0x%x\n", gpuidx);
                 pdd = kfd_process_device_from_gpuidx(p, gpuidx);
                 if (!pdd) {
                         pr_debug("failed to find device idx %d\n", gpuidx);
-                       return -EINVAL;
+                       continue;
+               }
+
+               if (!svm_range_partial_mapped_dev(gpuidx, prange, start, last)) {
+                       pr_debug("svms 0x%p prange 0x%p [0x%lx 0x%lx] not mapped on gpu %d\n",
+                                prange->svms, prange, start, last, gpuidx);
+                       continue;
                 }

+               svm_range_update_mapped(gpuidx, prange, start, last, false);
+
+               pr_debug("unmap svms 0x%p prange 0x%p [0x%lx 0x%lx] from gpu %d\n",
+                        prange->svms, prange, start, last, gpuidx);
+
                 kfd_smi_event_unmap_from_gpu(pdd->dev, p->lead_thread->pid,
                                              start, last, trigger);

@@ -1483,6 +1620,10 @@ svm_range_map_to_gpus(struct svm_range *prange, unsigned long offset,
                 if (r)
                         break;

+               if (!r)
+                       svm_range_update_mapped(gpuidx, prange, prange->start + offset,
+                                               prange->start + offset + npages - 1, true);

svm_range_update_mapped set the mapping bitmap with prange->granularity, but the gpu mapping is for [prange->start + offset,  prange->start + offset + npages - 1]. The mapping bitmap covered range maybe bigger then the range that got mapped.

In following gpu page fault handler you use svm_range_partial_mapped_dev(gpuidx, prange, addr, addr) to check if addr is mapped. Is there a room left that addr is not mapped, but the mapping bitmap covers it? That would cause the page fault at addr never got handled.

Regard

Xiaogang

+
                 if (fence) {
                         r = dma_fence_wait(fence, false);
                         dma_fence_put(fence);
@@ -1648,7 +1789,7 @@ static int svm_range_validate_and_map(struct mm_struct *mm,

         if (bitmap_empty(ctx->bitmap, MAX_GPU_INSTANCE)) {
                 bitmap_copy(ctx->bitmap, prange->bitmap_access, MAX_GPU_INSTANCE);
-               if (!prange->mapped_to_gpu ||
+               if (!svm_range_is_mapped(prange) ||
                     bitmap_empty(ctx->bitmap, MAX_GPU_INSTANCE)) {
                         r = 0;
                         goto free_ctx;
@@ -1729,9 +1870,6 @@ static int svm_range_validate_and_map(struct mm_struct *mm,
                         r = svm_range_map_to_gpus(prange, offset, npages, readonly,
                                                   ctx->bitmap, flush_tlb);

-               if (!r && next == end)
-                       prange->mapped_to_gpu = true;
-
                 svm_range_unlock(prange);

                 addr = next;
@@ -1900,10 +2038,10 @@ svm_range_evict(struct svm_range *prange, struct mm_struct *mm,
         if (!p->xnack_enabled ||
             (prange->flags & KFD_IOCTL_SVM_FLAG_GPU_ALWAYS_MAPPED)) {
                 int evicted_ranges;
-               bool mapped = prange->mapped_to_gpu;
+               bool mapped = svm_range_is_mapped(prange);

                 list_for_each_entry(pchild, &prange->child_list, child_list) {
-                       if (!pchild->mapped_to_gpu)
+                       if (!svm_range_is_mapped(pchild))
                                 continue;
                         mapped = true;
                         mutex_lock_nested(&pchild->lock, 1);
@@ -1966,7 +2104,9 @@ svm_range_evict(struct svm_range *prange, struct mm_struct *mm,

  static struct svm_range *svm_range_clone(struct svm_range *old)
  {
+       struct kfd_process *p = container_of(old->svms, struct kfd_process, svms);
         struct svm_range *new;
+       uint32_t gpuidx;

         new = svm_range_new(old->svms, old->start, old->last, false);
         if (!new)
@@ -1988,7 +2128,11 @@ static struct svm_range *svm_range_clone(struct svm_range *old)
         new->prefetch_loc = old->prefetch_loc;
         new->actual_loc = old->actual_loc;
         new->granularity = old->granularity;
-       new->mapped_to_gpu = old->mapped_to_gpu;
+       for_each_set_bit(gpuidx, p->svms.bitmap_supported, p->n_pdds) {
+               bitmap_copy(new->bitmap_mapped[gpuidx], old->bitmap_mapped[gpuidx],
+                           svm_range_mapped_nbits(new->last - new->start + 1,
+                                                  new->granularity));
+       };
         bitmap_copy(new->bitmap_access, old->bitmap_access, MAX_GPU_INSTANCE);
         bitmap_copy(new->bitmap_aip, old->bitmap_aip, MAX_GPU_INSTANCE);

@@ -2107,7 +2251,7 @@ svm_range_add(struct kfd_process *p, uint64_t start, uint64_t size,
                 next_start = min(node->last, last) + 1;

                 if (svm_range_is_same_attrs(p, prange, nattr, attrs) &&
-                   prange->mapped_to_gpu) {
+                   svm_range_is_mapped(prange)) {
                         /* nothing to do */
                 } else if (node->start < start || node->last > last) {
                         /* node intersects the update range and its attributes
@@ -3587,7 +3731,7 @@ svm_range_set_attr(struct kfd_process *p, struct mm_struct *mm,

                 if (migrated && (!p->xnack_enabled ||
                     (prange->flags & KFD_IOCTL_SVM_FLAG_GPU_ALWAYS_MAPPED)) &&
-                   prange->mapped_to_gpu) {
+                   svm_range_is_mapped(prange)) {
                         pr_debug("restore_work will update mappings of GPUs\n");
                         mutex_unlock(&prange->migrate_mutex);
                         continue;
@@ -3598,7 +3742,7 @@ svm_range_set_attr(struct kfd_process *p, struct mm_struct *mm,
                         continue;
                 }

-               flush_tlb = !migrated && update_mapping && prange->mapped_to_gpu;
+               flush_tlb = !migrated && update_mapping && svm_range_is_mapped(prange);

                 r = svm_range_validate_and_map(mm, prange, MAX_GPU_INSTANCE,
                                                true, flush_tlb);
diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_svm.h b/drivers/gpu/drm/amd/amdkfd/kfd_svm.h
index d2e94d8fb4be..10c92c5e23a7 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_svm.h
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_svm.h
@@ -132,7 +132,7 @@ struct svm_range {
         struct list_head                child_list;
         DECLARE_BITMAP(bitmap_access, MAX_GPU_INSTANCE);
         DECLARE_BITMAP(bitmap_aip, MAX_GPU_INSTANCE);
-       bool                            mapped_to_gpu;
+       unsigned long                   *bitmap_mapped[MAX_GPU_INSTANCE];
  };

  static inline void svm_range_lock(struct svm_range *prange)
@@ -163,6 +163,8 @@ static inline struct svm_range_bo *svm_range_bo_ref(struct svm_range_bo *svm_bo)
                 return NULL;
  }

+#define svm_range_mapped_nbits(size, granularity) DIV_ROUND_UP((size), 1UL << (granularity))
+
  int svm_range_list_init(struct kfd_process *p);
  void svm_range_list_fini(struct kfd_process *p);
  int svm_ioctl(struct kfd_process *p, enum kfd_ioctl_svm_op op, uint64_t start,
--
2.35.1




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