[PATCH] drm/amdgpu: Let userptr BO ttm have TTM_PAGE_FLAG_SG set

[xinhui pan <xinhui.pan@xxxxxxx>]

We have met memory corruption due to unexcepted swapout/swapin.

swapout function create one swap storage which is filled with zero. And
set ttm->page_flags as TTM_PAGE_FLAG_SWAPPED. But because userptr BO ttm
has no backend page at that time, no real data is swapout to swap
storage.

swapin function is called during userptr BO populate as
TTM_PAGE_FLAG_SWAPPED is set. Now here is the problem, we swapin data to
ttm bakend memory from swap storage. That just causes the memory been
overwritten.

CPU 1						CPU 2
kfd alloc BO A(userptr)                         alloc BO B(GTT)
    ->init -> validate(create ttm)		-> init -> validate -> populate
    init_user_pages                               -> swapout BO A
        -> get_user_pages (fill up ttm->pages)
         -> validate -> populate
          -> swapin BO A // memory overwritten

To fix this issue, we can set TTM_PAGE_FLAG_SG when we create userptr BO
ttm. Then swapout function would not swap it.

Signed-off-by: xinhui pan <xinhui.pan@xxxxxxx>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c | 4 +---
 drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c          | 4 ++++
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
index 928e8d57cd08..9a6ea966ddb2 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
@@ -1410,7 +1410,7 @@ int amdgpu_amdkfd_gpuvm_alloc_memory_of_gpu(
 	} else if (flags & KFD_IOC_ALLOC_MEM_FLAGS_USERPTR) {
 		domain = AMDGPU_GEM_DOMAIN_GTT;
 		alloc_domain = AMDGPU_GEM_DOMAIN_CPU;
-		alloc_flags = 0;
+		alloc_flags = AMDGPU_AMDKFD_CREATE_USERPTR_BO;
 		if (!offset || !*offset)
 			return -EINVAL;
 		user_addr = untagged_addr(*offset);
@@ -1477,8 +1477,6 @@ int amdgpu_amdkfd_gpuvm_alloc_memory_of_gpu(
 	}
 	bo->kfd_bo = *mem;
 	(*mem)->bo = bo;
-	if (user_addr)
-		bo->flags |= AMDGPU_AMDKFD_CREATE_USERPTR_BO;
 
 	(*mem)->va = va;
 	(*mem)->domain = domain;
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
index c7f5cc503601..5b3f45637fb5 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
@@ -1119,6 +1119,10 @@ static struct ttm_tt *amdgpu_ttm_tt_create(struct ttm_buffer_object *bo,
 		kfree(gtt);
 		return NULL;
 	}
+
+	if (abo->flags & AMDGPU_AMDKFD_CREATE_USERPTR_BO)
+		gtt->ttm.page_flags |= TTM_PAGE_FLAG_SG;
+
 	return &gtt->ttm;
 }
 
-- 
2.25.1