[Intel-gfx] [PATCH 33/61] drm/i915: Add ww locking around vm_access()

Maarten Lankhorst
2020-10-02T13:00:18Z

i915_gem_object_pin_map potentially needs a ww context, so ensure we
have one we can revoke.

Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
---
drivers/gpu/drm/i915/gem/i915_gem_mman.c | 24 ++++++++++++++++++++++--
1 file changed, 22 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_mman.c b/drivers/gpu/drm/i915/gem/i915_gem_mman.c
index ba8e9ef6943d..1361eabea966 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_mman.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_mman.c
@@ -421,7 +421,9 @@ vm_access(struct vm_area_struct *area, unsigned long addr,
{
struct i915_mmap_offset *mmo = area->vm_private_data;
struct drm_i915_gem_object *obj = mmo->obj;
+ struct i915_gem_ww_ctx ww;
void *vaddr;
+ int err = 0;

if (i915_gem_object_is_readonly(obj) && write)
return -EACCES;
@@ -430,10 +432,18 @@ vm_access(struct vm_area_struct *area, unsigned long addr,
if (addr >= obj->base.size)
return -EINVAL;

+ i915_gem_ww_ctx_init(&ww, true);
+retry:
+ err = i915_gem_object_lock(obj, &ww);
+ if (err)
+ goto out;
+
/* As this is primarily for debugging, let's focus on simplicity */
vaddr = i915_gem_object_pin_map(obj, I915_MAP_FORCE_WC);
- if (IS_ERR(vaddr))
- return PTR_ERR(vaddr);
+ if (IS_ERR(vaddr)) {
+ err = PTR_ERR(vaddr);
+ goto out;
+ }

if (write) {
memcpy(vaddr + addr, buf, len);
@@ -443,6 +453,16 @@ vm_access(struct vm_area_struct *area, unsigned long addr,
}

i915_gem_object_unpin_map(obj);
+out:
+ if (err == -EDEADLK) {
+ err = i915_gem_ww_ctx_backoff(&ww);
+ if (!err)
+ goto retry;
+ }
+ i915_gem_ww_ctx_fini(&ww);
+
+ if (err)
+ return err;

return len;