On 9/22/2023 4:37 PM, Philip Yang wrote:
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Otherwise kfd flush tlb does nothing if vm update fence callback doesn't
update vm->tlb_seq. H/W will generate retry fault again.
This works now because retry fault keep coming, recover will update page
table again after AMDGPU_SVM_RANGE_RETRY_FAULT_PENDING timeout and flush
tlb.
I think what this patch does is waiting vm->last_update fence at gpu page fault retry handler. I do not know what bug it tries to fix. h/w will keep generating retry fault as long as vm page table is not setup correctly, no matter kfd driver waits the fence or not. vm page table eventually will be setup.
This issue was there, I notice it when implementing the
granularity bitmap_mapped flag for mGPUs, to skip the retry fault
if prange mapped on the GPU. The retry fault keep coming after
updating GPU page table, because restore_pages ->
svm_range_validate_and_map doesn't wait for vm update fence before
kfd_flush_tlb.
It is working now because we handle the same retry fault again
after timeout AMDGPU_SVM_RANGE_RETRY_FAULT_PENDING, and
kfd_flush_tlb does flush on the second time.
The issue only exist if using sdma update GPU page table, as no fence if cpu update GPU page table.
There are several todo items to optimize this further:
A. After updating GPU page table, we only wait for fence and
flush tlb if updating existing mapping, or vm params.table_freed
(this needs amdgpu vm interface change).
B. Use sync to wait mGPUs update fences.
C. Use multiple workers to handle restore_pages.
There is a consequence I saw: if we wait vm page table update fence it will delay gpu page fault handler exit. Then more h/w interrupt vectors will be sent to sw ring, potentially cause the ring overflow.
retry CAM filter, or sw filter drop the duplicate retry fault, to prevent sw ring overflow.
Regards,
Philip
Regards
Xiaogang
Remove wait parameter in svm_range_validate_and_map because it is
always called with true.
Signed-off-by: Philip Yang <philip.y...@amd.com>
---
drivers/gpu/drm/amd/amdkfd/kfd_svm.c | 15 +++++++--------
1 file changed, 7 insertions(+), 8 deletions(-)
diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
index 70aa882636ab..61f4de1633a8 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
@@ -1447,7 +1447,7 @@ svm_range_map_to_gpu(struct kfd_process_device *pdd, struct svm_range *prange,
static int
svm_range_map_to_gpus(struct svm_range *prange, unsigned long offset,
unsigned long npages, bool readonly,
- unsigned long *bitmap, bool wait, bool flush_tlb)
+ unsigned long *bitmap, bool flush_tlb)
{
struct kfd_process_device *pdd;
struct amdgpu_device *bo_adev = NULL;
@@ -1480,8 +1480,7 @@ svm_range_map_to_gpus(struct svm_range *prange, unsigned long offset,
r = svm_range_map_to_gpu(pdd, prange, offset, npages, readonly,
prange->dma_addr[gpuidx],
- bo_adev, wait ? &fence : NULL,
- flush_tlb);
+ bo_adev, &fence, flush_tlb);
if (r)
break;
@@ -1605,7 +1604,7 @@ static void *kfd_svm_page_owner(struct kfd_process *p, int32_t gpuidx)
*/
static int svm_range_validate_and_map(struct mm_struct *mm,
struct svm_range *prange, int32_t gpuidx,
- bool intr, bool wait, bool flush_tlb)
+ bool intr, bool flush_tlb)
{
struct svm_validate_context *ctx;
unsigned long start, end, addr;
@@ -1729,7 +1728,7 @@ static int svm_range_validate_and_map(struct mm_struct *mm,
if (!r)
r = svm_range_map_to_gpus(prange, offset, npages, readonly,
- ctx->bitmap, wait, flush_tlb);
+ ctx->bitmap, flush_tlb);
if (!r && next == end)
prange->mapped_to_gpu = true;
@@ -1823,7 +1822,7 @@ static void svm_range_restore_work(struct work_struct *work)
mutex_lock(&prange->migrate_mutex);
r = svm_range_validate_and_map(mm, prange, MAX_GPU_INSTANCE,
- false, true, false);
+ false, false);
if (r)
pr_debug("failed %d to map 0x%lx to gpus\n", r,
prange->start);
@@ -3064,7 +3063,7 @@ svm_range_restore_pages(struct amdgpu_device *adev, unsigned int pasid,
}
}
- r = svm_range_validate_and_map(mm, prange, gpuidx, false, false, false);
+ r = svm_range_validate_and_map(mm, prange, gpuidx, false, false);
if (r)
pr_debug("failed %d to map svms 0x%p [0x%lx 0x%lx] to gpus\n",
r, svms, prange->start, prange->last);
@@ -3603,7 +3602,7 @@ svm_range_set_attr(struct kfd_process *p, struct mm_struct *mm,
flush_tlb = !migrated && update_mapping && prange->mapped_to_gpu;
r = svm_range_validate_and_map(mm, prange, MAX_GPU_INSTANCE,
- true, true, flush_tlb);
+ true, flush_tlb);
if (r)
pr_debug("failed %d to map svm range\n", r);
--
2.35.1
