[PATCH 5.15 079/167] drm/i915: Require the vm mutex for i915_vma_bind()

Greg Kroah-Hartman
2022-07-19T12:36:17Z

From: Thomas Hellström <thomas.hellstrom@linux.intel.com>

[ Upstream commit c2ea703dcafccf18d7d77d8b68fb08c2d9842b7a ]

Protect updates of struct i915_vma flags and async binding / unbinding
with the vm::mutex. This means that i915_vma_bind() needs to assert
vm::mutex held. In order to make that possible drop the caching of
kmap_atomic() maps around i915_vma_bind().

An alternative would be to use kmap_local() but since we block cpu
unplugging during sleeps inside kmap_local() sections this may have
unwanted side-effects. Particularly since we might wait for gpu while
holding the vm mutex.

This change may theoretically increase execbuf cpu-usage on snb, but
at least on non-highmem systems that increase should be very small.

Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211221200050.436316-5-thomas.hellstrom@linux.intel.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
.../gpu/drm/i915/gem/i915_gem_execbuffer.c | 50 ++++++++++++++++++-
drivers/gpu/drm/i915/i915_vma.c | 1 +
2 files changed, 50 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
index 1aa249908b64..0d480867fc0c 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
@@ -1060,6 +1060,47 @@ static inline struct i915_ggtt *cache_to_ggtt(struct reloc_cache *cache)
return &i915->ggtt;
}

+static void reloc_cache_unmap(struct reloc_cache *cache)
+{
+ void *vaddr;
+
+ if (!cache->vaddr)
+ return;
+
+ vaddr = unmask_page(cache->vaddr);
+ if (cache->vaddr & KMAP)
+ kunmap_atomic(vaddr);
+ else
+ io_mapping_unmap_atomic((void __iomem *)vaddr);
+}
+
+static void reloc_cache_remap(struct reloc_cache *cache,
+ struct drm_i915_gem_object *obj)
+{
+ void *vaddr;
+
+ if (!cache->vaddr)
+ return;
+
+ if (cache->vaddr & KMAP) {
+ struct page *page = i915_gem_object_get_page(obj, cache->page);
+
+ vaddr = kmap_atomic(page);
+ cache->vaddr = unmask_flags(cache->vaddr) |
+ (unsigned long)vaddr;
+ } else {
+ struct i915_ggtt *ggtt = cache_to_ggtt(cache);
+ unsigned long offset;
+
+ offset = cache->node.start;
+ if (!drm_mm_node_allocated(&cache->node))
+ offset += cache->page << PAGE_SHIFT;
+
+ cache->vaddr = (unsigned long)
+ io_mapping_map_atomic_wc(&ggtt->iomap, offset);
+ }
+}
+
static void reloc_cache_reset(struct reloc_cache *cache, struct i915_execbuffer *eb)
{
void *vaddr;
@@ -1324,10 +1365,17 @@ eb_relocate_entry(struct i915_execbuffer *eb,
* batchbuffers.
*/
if (reloc->write_domain == I915_GEM_DOMAIN_INSTRUCTION &&
- GRAPHICS_VER(eb->i915) == 6) {
+ GRAPHICS_VER(eb->i915) == 6 &&
+ !i915_vma_is_bound(target->vma, I915_VMA_GLOBAL_BIND)) {
+ struct i915_vma *vma = target->vma;
+
+ reloc_cache_unmap(&eb->reloc_cache);
+ mutex_lock(&vma->vm->mutex);
err = i915_vma_bind(target->vma,
target->vma->obj->cache_level,
PIN_GLOBAL, NULL);
+ mutex_unlock(&vma->vm->mutex);
+ reloc_cache_remap(&eb->reloc_cache, ev->vma->obj);
if (err)
return err;
}
diff --git a/drivers/gpu/drm/i915/i915_vma.c b/drivers/gpu/drm/i915/i915_vma.c
index dfd20060812b..3df304edabc7 100644
--- a/drivers/gpu/drm/i915/i915_vma.c
+++ b/drivers/gpu/drm/i915/i915_vma.c
@@ -376,6 +376,7 @@ int i915_vma_bind(struct i915_vma *vma,
u32 bind_flags;
u32 vma_flags;

+ lockdep_assert_held(&vma->vm->mutex);
GEM_BUG_ON(!drm_mm_node_allocated(&vma->node));
GEM_BUG_ON(vma->size > vma->node.size);

--
2.35.1