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

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Message-ID: <14063C7AD467DE4B82DEDB5C278E8663FFFBD444@fmsmsx107.amr.corp.intel.com>
Date:   Wed, 25 Mar 2020 14:00:24 +0000
From:   "Ruhl, Michael J" <michael.j.ruhl@...el.com>
To:     Shane Francis <bigbeeshane@...il.com>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>
CC:     "airlied@...ux.ie" <airlied@...ux.ie>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "amd-gfx-request@...ts.freedesktop.org" 
        <amd-gfx-request@...ts.freedesktop.org>,
        "alexander.deucher@....com" <alexander.deucher@....com>,
        "christian.koenig@....com" <christian.koenig@....com>
Subject: RE: [PATCH v4 2/3] drm/amdgpu: fix scatter-gather mapping with user
 pages

>-----Original Message-----
>From: dri-devel <dri-devel-bounces@...ts.freedesktop.org> On Behalf Of
>Shane Francis
>Sent: Wednesday, March 25, 2020 5:08 AM
>To: dri-devel@...ts.freedesktop.org
>Cc: airlied@...ux.ie; linux-kernel@...r.kernel.org; bigbeeshane@...il.com;
>amd-gfx-request@...ts.freedesktop.org; alexander.deucher@....com;
>christian.koenig@....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

"may return less segments/entries" ?
                       ^^^
>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;

this looks correct to me.

Reviewed-by: Michael J. Ruhl <michael.j.ruhl@...el.com>

> 	/* convert SG to linear array of pages and dma addresses */
>--
>2.26.0
>
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>dri-devel mailing list
>dri-devel@...ts.freedesktop.org
>https://lists.freedesktop.org/mailman/listinfo/dri-devel

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