linux-kernel - [PATCH review for 4.9 27/50] drm/amdgpu: refuse to reserve io mem for split VRAM buffers

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Message-ID: <20170925011225.10029-27-alexander.levin@verizon.com>
Date:   Mon, 25 Sep 2017 01:12:51 +0000
From:   "Levin, Alexander (Sasha Levin)" <alexander.levin@...izon.com>
To:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Cc:     Nicolai Hähnle <nicolai.haehnle@....com>,
        Alex Deucher <alexander.deucher@....com>,
        "Levin, Alexander (Sasha Levin)" <alexander.levin@...izon.com>
Subject: [PATCH review for 4.9 27/50] drm/amdgpu: refuse to reserve io mem for
 split VRAM buffers

From: Nicolai Hähnle <nicolai.haehnle@....com>

[ Upstream commit 4694335dad7357e9b3d7822ab13049014d74d8b0 ]

When the fast blit path fails while attempting to move a buffer from RAM
to VRAM, we fall back to a CPU-based memcpy that cannot handle split VRAM
buffers. Instead of crashing, simply fail the buffer move.

Ideally, we would teach TTM about split buffers so that the fallback still
works in this case, but that is quite involved. So for now, apply the
simplest possible fix.

Fixes: 40361bb1704b ("drm/amdgpu: add VRAM manager v2")
Signed-off-by: Nicolai Hähnle <nicolai.haehnle@....com>
Reviewed-by: Christian König <christian.koenig@....com>
Signed-off-by: Alex Deucher <alexander.deucher@....com>
Signed-off-by: Sasha Levin <alexander.levin@...izon.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
index 264899df9bfc..05ff98b43c50 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
@@ -491,6 +491,9 @@ static int amdgpu_ttm_io_mem_reserve(struct ttm_bo_device *bdev, struct ttm_mem_
 	case TTM_PL_TT:
 		break;
 	case TTM_PL_VRAM:
+		if (mem->start == AMDGPU_BO_INVALID_OFFSET)
+			return -EINVAL;
+
 		mem->bus.offset = mem->start << PAGE_SHIFT;
 		/* check if it's visible */
 		if ((mem->bus.offset + mem->bus.size) > adev->mc.visible_vram_size)
-- 
2.11.0