This reverts commit 7dc8f1143778 ("drm/i915/gem: Drop relocation
slowpath"). We need the slowpath relocation for taking ww-mutex
inside the page fault handler, and we will take this mutex when
pinning all objects.
Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Matthew Auld <matthew.auld@xxxxxxxxx>
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx>
---
.../gpu/drm/i915/gem/i915_gem_execbuffer.c | 239 +++++++++++++++++-
1 file changed, 235 insertions(+), 4 deletions(-)
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
index c643eec4dca0..b451aac69211 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
@@ -1480,7 +1480,9 @@ static int eb_relocate_vma(struct i915_execbuffer *eb, struct eb_vma *ev)
* we would try to acquire the struct mutex again. Obviously
* this is bad and so lockdep complains vehemently.
*/
- copied = __copy_from_user(r, urelocs, count * sizeof(r[0]));
+ pagefault_disable();
+ copied = __copy_from_user_inatomic(r, urelocs, count * sizeof(r[0]));
+ pagefault_enable();
if (unlikely(copied)) {
remain = -EFAULT;
goto out;
@@ -1530,6 +1532,236 @@ static int eb_relocate_vma(struct i915_execbuffer *eb, struct eb_vma *ev)
return remain;
}
+static int
+eb_relocate_vma_slow(struct i915_execbuffer *eb, struct eb_vma *ev)
+{
+ const struct drm_i915_gem_exec_object2 *entry = ev->exec;
+ struct drm_i915_gem_relocation_entry *relocs =
+ u64_to_ptr(typeof(*relocs), entry->relocs_ptr);
+ unsigned int i;
+ int err;
+
+ for (i = 0; i < entry->relocation_count; i++) {
+ u64 offset = eb_relocate_entry(eb, ev, &relocs[i]);
+
+ if ((s64)offset < 0) {
+ err = (int)offset;
+ goto err;
+ }
+ }
+ err = 0;
+err:
+ reloc_cache_reset(&eb->reloc_cache);
+ return err;
+}
+
+static int check_relocations(const struct drm_i915_gem_exec_object2 *entry)
+{
+ const char __user *addr, *end;
+ unsigned long size;
+ char __maybe_unused c;
+
+ size = entry->relocation_count;
+ if (size == 0)
+ return 0;
+
+ if (size > N_RELOC(ULONG_MAX))
+ return -EINVAL;
+
+ addr = u64_to_user_ptr(entry->relocs_ptr);
+ size *= sizeof(struct drm_i915_gem_relocation_entry);
+ if (!access_ok(addr, size))
+ return -EFAULT;
+
+ end = addr + size;
+ for (; addr < end; addr += PAGE_SIZE) {
+ int err = __get_user(c, addr);
+ if (err)
+ return err;
+ }
+ return __get_user(c, end - 1);
+}
+
+static int eb_copy_relocations(const struct i915_execbuffer *eb)
+{
+ struct drm_i915_gem_relocation_entry *relocs;
+ const unsigned int count = eb->buffer_count;
+ unsigned int i;
+ int err;
+
+ for (i = 0; i < count; i++) {
+ const unsigned int nreloc = eb->exec[i].relocation_count;
+ struct drm_i915_gem_relocation_entry __user *urelocs;
+ unsigned long size;
+ unsigned long copied;
+
+ if (nreloc == 0)
+ continue;
+
+ err = check_relocations(&eb->exec[i]);
+ if (err)
+ goto err;
+
+ urelocs = u64_to_user_ptr(eb->exec[i].relocs_ptr);
+ size = nreloc * sizeof(*relocs);
+
+ relocs = kvmalloc_array(size, 1, GFP_KERNEL);
+ if (!relocs) {
+ err = -ENOMEM;
+ goto err;
+ }
+
+ /* copy_from_user is limited to < 4GiB */
+ copied = 0;
+ do {
+ unsigned int len =
+ min_t(u64, BIT_ULL(31), size - copied);
+
+ if (__copy_from_user((char *)relocs + copied,
+ (char __user *)urelocs + copied,
+ len))
+ goto end;
+
+ copied += len;
+ } while (copied < size);
+
+ /*
+ * As we do not update the known relocation offsets after
+ * relocating (due to the complexities in lock handling),
+ * we need to mark them as invalid now so that we force the
+ * relocation processing next time. Just in case the target
+ * object is evicted and then rebound into its old
+ * presumed_offset before the next execbuffer - if that
+ * happened we would make the mistake of assuming that the
+ * relocations were valid.
+ */
+ if (!user_access_begin(urelocs, size))
+ goto end;
+
+ for (copied = 0; copied < nreloc; copied++)
+ unsafe_put_user(-1,
+ &urelocs[copied].presumed_offset,
+ end_user);
+ user_access_end();
+
+ eb->exec[i].relocs_ptr = (uintptr_t)relocs;
+ }
+
+ return 0;
+
+end_user:
+ user_access_end();
+end:
+ kvfree(relocs);
+ err = -EFAULT;
+err:
+ while (i--) {
+ relocs = u64_to_ptr(typeof(*relocs), eb->exec[i].relocs_ptr);
+ if (eb->exec[i].relocation_count)
+ kvfree(relocs);
+ }
+ return err;
+}
+
+static int eb_prefault_relocations(const struct i915_execbuffer *eb)
+{
+ const unsigned int count = eb->buffer_count;
+ unsigned int i;
+
+ for (i = 0; i < count; i++) {
+ int err;
+
+ err = check_relocations(&eb->exec[i]);
+ if (err)
+ return err;
+ }
+
+ return 0;
+}
+
+static noinline int eb_relocate_slow(struct i915_execbuffer *eb)
+{
+ bool have_copy = false;
+ struct eb_vma *ev;
+ int err = 0;
+
+repeat:
+ if (signal_pending(current)) {
+ err = -ERESTARTSYS;
+ goto out;
+ }
+
+ /*
+ * We take 3 passes through the slowpatch.
+ *
+ * 1 - we try to just prefault all the user relocation entries and
+ * then attempt to reuse the atomic pagefault disabled fast path again.
+ *
+ * 2 - we copy the user entries to a local buffer here outside of the
+ * local and allow ourselves to wait upon any rendering before
+ * relocations
+ *
+ * 3 - we already have a local copy of the relocation entries, but
+ * were interrupted (EAGAIN) whilst waiting for the objects, try again.
+ */
+ if (!err) {
+ err = eb_prefault_relocations(eb);
+ } else if (!have_copy) {
+ err = eb_copy_relocations(eb);
+ have_copy = err == 0;
+ } else {
+ cond_resched();
+ err = 0;
+ }
+ if (err)
+ goto out;
+
+ list_for_each_entry(ev, &eb->relocs, reloc_link) {
+ if (!have_copy) {
+ pagefault_disable();
+ err = eb_relocate_vma(eb, ev);
+ pagefault_enable();
+ if (err)
+ goto repeat;
+ } else {
+ err = eb_relocate_vma_slow(eb, ev);
+ if (err)
+ goto err;
+ }
+ }
+
+ /*
+ * Leave the user relocations as are, this is the painfully slow path,
+ * and we want to avoid the complication of dropping the lock whilst
+ * having buffers reserved in the aperture and so causing spurious
+ * ENOSPC for random operations.
+ */
+
+err:
+ if (err == -EAGAIN)
+ goto repeat;
+
+out:
+ if (have_copy) {
+ const unsigned int count = eb->buffer_count;
+ unsigned int i;
+
+ for (i = 0; i < count; i++) {
+ const struct drm_i915_gem_exec_object2 *entry =
+ &eb->exec[i];
+ struct drm_i915_gem_relocation_entry *relocs;
+
+ if (!entry->relocation_count)
+ continue;
+
+ relocs = u64_to_ptr(typeof(*relocs), entry->relocs_ptr);
+ kvfree(relocs);
+ }
+ }
+
+ return err;
+}
+
static int eb_relocate(struct i915_execbuffer *eb)
{
int err;
@@ -1549,9 +1781,8 @@ static int eb_relocate(struct i915_execbuffer *eb)
struct eb_vma *ev;
list_for_each_entry(ev, &eb->relocs, reloc_link) {
- err = eb_relocate_vma(eb, ev);
- if (err)
- return err;
+ if (eb_relocate_vma(eb, ev))
+ return eb_relocate_slow(eb);
}
}
--
2.25.1
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