linux-kernel - [PATCH v4 2/3] drm/amdgpu: fix scatter-gather mapping with user pages

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Message-Id: <20200325090741.21957-3-bigbeeshane@gmail.com>
Date:   Wed, 25 Mar 2020 09:07:40 +0000
From:   Shane Francis <bigbeeshane@...il.com>
To:     dri-devel@...ts.freedesktop.org
Cc:     amd-gfx-request@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, bigbeeshane@...il.com,
        alexander.deucher@....com, christian.koenig@....com,
        mripard@...nel.org, airlied@...ux.ie, David1.Zhou@....com
Subject: [PATCH v4 2/3] drm/amdgpu: fix scatter-gather mapping with user pages

Calls to dma_map_sg may return segments / entries than requested
if they fall on page bounderies. The old implementation did not
support this use case.

Signed-off-by: Shane Francis <bigbeeshane@...il.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
index dee446278417..c6e9885c071f 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
@@ -974,7 +974,7 @@ static int amdgpu_ttm_tt_pin_userptr(struct ttm_tt *ttm)
 	/* Map SG to device */
 	r = -ENOMEM;
 	nents = dma_map_sg(adev->dev, ttm->sg->sgl, ttm->sg->nents, direction);
-	if (nents != ttm->sg->nents)
+	if (nents == 0)
 		goto release_sg;
 
 	/* convert SG to linear array of pages and dma addresses */
-- 
2.26.0