Swapping SG BOs makes no sense, because TTM doesn't own the pages of
this type of BO.
Last I checked, userptr BOs (and other SG BOs) were protected from
swapout by the fact that they would not be added to the swap-LRU. But it
looks like Christian just removed the swap-LRU. I guess this broke that
protection:
commit 2cb51d22d70b18eaf339abf9758bf0b7608da65c
Author: Christian König <christian.koenig@xxxxxxx>
Date: Tue Oct 6 16:30:09 2020 +0200
drm/ttm: remove swap LRU v3
Instead evict round robin from each devices SYSTEM and TT domain.
v2: reorder num_pages access reported by Dan's script
v3: fix rebase fallout, num_pages should be 32bit
Signed-off-by: Christian König <christian.koenig@xxxxxxx>
Tested-by: Nirmoy Das <nirmoy.das@xxxxxxx>
Reviewed-by: Huang Rui <ray.huang@xxxxxxx>
Reviewed-by: Matthew Auld <matthew.auld@xxxxxxxxx>
Link: https://patchwork.freedesktop.org/patch/424009/
Regards,
Felix
On 2021-05-18 10:28 p.m., xinhui pan wrote:
cpu 1 cpu 2
kfd alloc BO A(userptr) alloc BO B(GTT)
->init -> validate -> init -> validate -> populate
init_user_pages -> swapout BO A //hit ttm pages limit
-> get_user_pages (fill up ttm->pages)
-> validate -> populate
-> swapin BO A // Now hit the BUG
We know that get_user_pages may race with swapout on same BO.
Threre are some issues I have met.
1) memory corruption.
This is because we do a swap before memory is setup. ttm_tt_swapout()
just create a swap_storage with its content being 0x0. So when we setup
memory after the swapout. The following swapin makes the memory
corrupted.
2) panic
When swapout happes with get_user_pages, they touch ttm->pages without
anylock. It causes memory corruption too. But I hit page fault mostly.
Signed-off-by: xinhui pan <xinhui.pan@xxxxxxx>
---
drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c | 16 +++++++++++++++-
1 file changed, 15 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
index 928e8d57cd08..42460e4480f8 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
@@ -835,6 +835,7 @@ static int init_user_pages(struct kgd_mem *mem, uint64_t user_addr)
struct amdkfd_process_info *process_info = mem->process_info;
struct amdgpu_bo *bo = mem->bo;
struct ttm_operation_ctx ctx = { true, false };
+ struct page **pages;
int ret = 0;
mutex_lock(&process_info->lock);
@@ -852,7 +853,13 @@ static int init_user_pages(struct kgd_mem *mem, uint64_t user_addr)
goto out;
}
- ret = amdgpu_ttm_tt_get_user_pages(bo, bo->tbo.ttm->pages);
+ pages = kvmalloc_array(bo->tbo.ttm->num_pages,
+ sizeof(struct page *),
+ GFP_KERNEL | __GFP_ZERO);
+ if (!pages)
+ goto unregister_out;
+
+ ret = amdgpu_ttm_tt_get_user_pages(bo, pages);
if (ret) {
pr_err("%s: Failed to get user pages: %d\n", __func__, ret);
goto unregister_out;
@@ -863,6 +870,12 @@ static int init_user_pages(struct kgd_mem *mem, uint64_t user_addr)
pr_err("%s: Failed to reserve BO\n", __func__);
goto release_out;
}
+
+ WARN_ON_ONCE(bo->tbo.ttm->page_flags & TTM_PAGE_FLAG_SWAPPED);
+
+ memcpy(bo->tbo.ttm->pages,
+ pages,
+ sizeof(struct page*) * bo->tbo.ttm->num_pages);
amdgpu_bo_placement_from_domain(bo, mem->domain);
ret = ttm_bo_validate(&bo->tbo, &bo->placement, &ctx);
if (ret)
@@ -872,6 +885,7 @@ static int init_user_pages(struct kgd_mem *mem, uint64_t user_addr)
release_out:
amdgpu_ttm_tt_get_user_pages_done(bo->tbo.ttm);
unregister_out:
+ kvfree(pages);
if (ret)
amdgpu_mn_unregister(bo);
out:
