current/SOURCES/drm-i915-reserve-enough-fence-slot-for-i915_vma_unbind_async.patch

From 476fdcdaaae7b06c780cdfc234c704107f16c529 Mon Sep 17 00:00:00 2001
From: Nirmoy Das <nirmoy.das@intel.com>
Date: Fri, 23 Dec 2022 10:20:11 +0100
Subject: drm/i915: Reserve enough fence slot for i915_vma_unbind_async
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From: Nirmoy Das <nirmoy.das@intel.com>

commit 476fdcdaaae7b06c780cdfc234c704107f16c529 upstream.

A nested dma_resv_reserve_fences(1) will not reserve slot from the
2nd call onwards and folowing dma_resv_add_fence() might hit the
"BUG_ON(fobj->num_fences >= fobj->max_fences)" check.

I915 hit above nested dma_resv case in ttm_bo_handle_move_mem() with
async unbind:

dma_resv_reserve_fences() from --> ttm_bo_handle_move_mem()
        dma_resv_reserve_fences() from --> i915_vma_unbind_async()
        dma_resv_add_fence() from --> i915_vma_unbind_async()
dma_resv_add_fence() from -->ttm_bo_move_accel_cleanup()

Resolve this by adding an extra fence in i915_vma_unbind_async().

Suggested-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Fixes: 2f6b90da9192 ("drm/i915: Use vma resources for async unbinding")
Cc: <stable@vger.kernel.org> # v5.18+
Signed-off-by: Nirmoy Das <nirmoy.das@intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221223092011.11657-1-nirmoy.das@intel.com
(cherry picked from commit 4f0755c2faf7388616109717facc5bbde6850e60)
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/gpu/drm/i915/i915_vma.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/gpu/drm/i915/i915_vma.c
+++ b/drivers/gpu/drm/i915/i915_vma.c
@@ -2114,7 +2114,7 @@ int i915_vma_unbind_async(struct i915_vm
        if (!obj->mm.rsgt)
                return -EBUSY;
 
-       err = dma_resv_reserve_fences(obj->base.resv, 1);
+       err = dma_resv_reserve_fences(obj->base.resv, 2);
        if (err)
                return -EBUSY;
 
1	From 476fdcdaaae7b06c780cdfc234c704107f16c529 Mon Sep 17 00:00:00 2001
2	From: Nirmoy Das <nirmoy.das@intel.com>
3	Date: Fri, 23 Dec 2022 10:20:11 +0100
4	Subject: drm/i915: Reserve enough fence slot for i915_vma_unbind_async
5	MIME-Version: 1.0
6	Content-Type: text/plain; charset=UTF-8
7	Content-Transfer-Encoding: 8bit
8
9	From: Nirmoy Das <nirmoy.das@intel.com>
10
11	commit 476fdcdaaae7b06c780cdfc234c704107f16c529 upstream.
12
13	A nested dma_resv_reserve_fences(1) will not reserve slot from the
14	2nd call onwards and folowing dma_resv_add_fence() might hit the
15	"BUG_ON(fobj->num_fences >= fobj->max_fences)" check.
16
17	I915 hit above nested dma_resv case in ttm_bo_handle_move_mem() with
18	async unbind:
19
20	dma_resv_reserve_fences() from --> ttm_bo_handle_move_mem()
21	dma_resv_reserve_fences() from --> i915_vma_unbind_async()
22	dma_resv_add_fence() from --> i915_vma_unbind_async()
23	dma_resv_add_fence() from -->ttm_bo_move_accel_cleanup()
24
25	Resolve this by adding an extra fence in i915_vma_unbind_async().
26
27	Suggested-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
28	Fixes: 2f6b90da9192 ("drm/i915: Use vma resources for async unbinding")
29	Cc: <stable@vger.kernel.org> # v5.18+
30	Signed-off-by: Nirmoy Das <nirmoy.das@intel.com>
31	Reviewed-by: Matthew Auld <matthew.auld@intel.com>
32	Signed-off-by: Matthew Auld <matthew.auld@intel.com>
33	Link: https://patchwork.freedesktop.org/patch/msgid/20221223092011.11657-1-nirmoy.das@intel.com
34	(cherry picked from commit 4f0755c2faf7388616109717facc5bbde6850e60)
35	Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
36	Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
37	---
38	drivers/gpu/drm/i915/i915_vma.c \| 2 +-
39	1 file changed, 1 insertion(+), 1 deletion(-)
40
41	--- a/drivers/gpu/drm/i915/i915_vma.c
42	+++ b/drivers/gpu/drm/i915/i915_vma.c
43	@@ -2114,7 +2114,7 @@ int i915_vma_unbind_async(struct i915_vm
44	if (!obj->mm.rsgt)
45	return -EBUSY;
46
47	- err = dma_resv_reserve_fences(obj->base.resv, 1);
48	+ err = dma_resv_reserve_fences(obj->base.resv, 2);
49	if (err)
50	return -EBUSY;
51