Patchwork [3.5.y.z,extended,stable] Patch "drm/i915: Invalidate the relocation presumed_offsets along" has been added to staging queue

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Submitter Herton Ronaldo Krzesinski
Date Jan. 30, 2013, 9:57 p.m.
Message ID <1359583027-16992-1-git-send-email-herton.krzesinski@canonical.com>
Download mbox | patch
Permalink /patch/217039/
State New
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Comments

Herton Ronaldo Krzesinski - Jan. 30, 2013, 9:57 p.m.
This is a note to let you know that I have just added a patch titled

    drm/i915: Invalidate the relocation presumed_offsets along

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.5.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Herton

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From 1562e9ee4e0a36ee6bb7ff6b10a9a58d0bf39660 Mon Sep 17 00:00:00 2001
From: Chris Wilson <chris@chris-wilson.co.uk>
Date: Tue, 15 Jan 2013 16:17:54 +0000
Subject: [PATCH] drm/i915: Invalidate the relocation presumed_offsets along
 the slow path

commit 262b6d363fcff16359c93bd58c297f961f6e6273 upstream.

In the slow path, we are forced to copy the relocations prior to
acquiring the struct mutex in order to handle pagefaults. We forgo
copying the new offsets back into the relocation entries in order to
prevent a recursive locking bug should we trigger a pagefault whilst
holding the mutex for the reservations of the execbuffer. Therefore, we
need to reset the presumed_offsets just in case the objects are rebound
back into their old locations after relocating for this exexbuffer - if
that were to happen we would assume the relocations were valid and leave
the actual pointers to the kernels dangling, instant hang.

Fixes regression from commit bcf50e2775bbc3101932d8e4ab8c7902aa4163b4
Author: Chris Wilson <chris@chris-wilson.co.uk>
Date:   Sun Nov 21 22:07:12 2010 +0000

    drm/i915: Handle pagefaults in execbuffer user relocations

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=55984
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniel Vetter <daniel.vetter@fwll.ch>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Herton Ronaldo Krzesinski <herton.krzesinski@canonical.com>
---
 drivers/gpu/drm/i915/i915_gem_execbuffer.c |   21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

--
1.7.9.5

Patch

diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
index 3debf95..fadd6d6 100644
--- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
@@ -749,6 +749,8 @@  i915_gem_execbuffer_relocate_slow(struct drm_device *dev,
 	total = 0;
 	for (i = 0; i < count; i++) {
 		struct drm_i915_gem_relocation_entry __user *user_relocs;
+		u64 invalid_offset = (u64)-1;
+		int j;

 		user_relocs = (void __user *)(uintptr_t)exec[i].relocs_ptr;

@@ -759,6 +761,25 @@  i915_gem_execbuffer_relocate_slow(struct drm_device *dev,
 			goto err;
 		}

+		/* 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.
+		 */
+		for (j = 0; j < exec[i].relocation_count; j++) {
+			if (copy_to_user(&user_relocs[j].presumed_offset,
+					 &invalid_offset,
+					 sizeof(invalid_offset))) {
+				ret = -EFAULT;
+				mutex_lock(&dev->struct_mutex);
+				goto err;
+			}
+		}
+
 		reloc_offset[i] = total;
 		total += exec[i].relocation_count;
 	}