[PATCH AUTOSEL 6.18] drm/amdgpu: Handle GPU page faults correctly on non-4K page systems

[Sasha Levin]

From: Donet Tom <donettom@xxxxxxxxxxxxx>

[ Upstream commit 4e9597f22a3cb8600c72fc266eaac57981d834c8 ]

During a GPU page fault, the driver restores the SVM range and then maps it
into the GPU page tables. The current implementation passes a GPU-page-size
(4K-based) PFN to svm_range_restore_pages() to restore the range.

SVM ranges are tracked using system-page-size PFNs. On systems where the
system page size is larger than 4K, using GPU-page-size PFNs to restore the
range causes two problems:

Range lookup fails:
Because the restore function receives PFNs in GPU (4K) units, the SVM
range lookup does not find the existing range. This will result in a
duplicate SVM range being created.

VMA lookup failure:
The restore function also tries to locate the VMA for the faulting address.
It converts the GPU-page-size PFN into an address using the system page
size, which results in an incorrect address on non-4K page-size systems.
As a result, the VMA lookup fails with the message: "address 0xxxx VMA is
removed".

This patch passes the system-page-size PFN to svm_range_restore_pages() so
that the SVM range is restored correctly on non-4K page systems.

Acked-by: Christian König <christian.koenig@xxxxxxx>
Signed-off-by: Donet Tom <donettom@xxxxxxxxxxxxx>
Signed-off-by: Alex Deucher <alexander.deucher@xxxxxxx>
(cherry picked from commit 074fe395fb13247b057f60004c7ebcca9f38ef46)
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---

LLM Generated explanations, may be completely bogus:

Error: Failed to generate final synthesis

 drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
index f2e00f408156c..69080e3734891 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
@@ -2960,14 +2960,14 @@ bool amdgpu_vm_handle_fault(struct amdgpu_device *adev, u32 pasid,
 	if (!root)
 		return false;
 
-	addr /= AMDGPU_GPU_PAGE_SIZE;
-
 	if (is_compute_context && !svm_range_restore_pages(adev, pasid, vmid,
-	    node_id, addr, ts, write_fault)) {
+	    node_id, addr >> PAGE_SHIFT, ts, write_fault)) {
 		amdgpu_bo_unref(&root);
 		return true;
 	}
 
+	addr /= AMDGPU_GPU_PAGE_SIZE;
+
 	r = amdgpu_bo_reserve(root, true);
 	if (r)
 		goto error_unref;
-- 
2.53.0