drm/ttm: Restore ttm prefaulting

BugLink: https://bugs.launchpad.net/bugs/1850456
commit 941f2f72dbbe0cf8c2d6e0b180a8021a0ec477fa upstream.

Commit 4daa4fba3a38 ("gpu: drm: ttm: Adding new return type vm_fault_t")
broke TTM prefaulting. Since vmf_insert_mixed() typically always returns
VM_FAULT_NOPAGE, prefaulting stops after the second PTE.

Restore (almost) the original behaviour. Unfortunately we can no longer
with the new vm_fault_t return type determine whether a prefaulting
PTE insertion hit an already populated PTE, and terminate the insertion
loop. Instead we continue with the pre-determined number of prefaults.

Fixes: 4daa4fba3a38 ("gpu: drm: ttm: Adding new return type vm_fault_t")
Cc: Souptick Joarder <jrdr.linux@gmail.com>
Cc: Christian König <christian.koenig@amd.com>
Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Cc: stable@vger.kernel.org # v4.19+
Signed-off-by: Christian König <christian.koenig@amd.com>
Link: https://patchwork.freedesktop.org/patch/330387/
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Connor Kuehl <connor.kuehl@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

diff --git a/drivers/gpu/drm/ttm/ttm_bo_vm.c b/drivers/gpu/drm/ttm/ttm_bo_vm.c
index 6dacff49c1cc5a4944dc856365602f7b60b8de64..a77cd0344d228ee4dc0bea6a3be85ebf8dbcae18 100644 (file)
--- a/drivers/gpu/drm/ttm/ttm_bo_vm.c
+++ b/drivers/gpu/drm/ttm/ttm_bo_vm.c
@@ -278,15 +278,13 @@ static vm_fault_t ttm_bo_vm_fault(struct vm_fault *vmf)
                else
                        ret = vmf_insert_pfn(&cvma, address, pfn);
 
-               /*
-                * Somebody beat us to this PTE or prefaulting to
-                * an already populated PTE, or prefaulting error.
-                */
-
-               if (unlikely((ret == VM_FAULT_NOPAGE && i > 0)))
-                       break;
-               else if (unlikely(ret & VM_FAULT_ERROR))
-                       goto out_io_unlock;
+               /* Never error on prefaulted PTEs */
+               if (unlikely((ret & VM_FAULT_ERROR))) {
+                       if (i == 0)
+                               goto out_io_unlock;
+                       else
+                               break;
+               }
 
                address += PAGE_SIZE;
                if (unlikely(++page_offset >= page_last))