linux-kernel - [PATCH v2] drm/virtio: use virtio_max_dma

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Message-Id: <20190809141419.3353-1-kraxel@redhat.com>
Date:   Fri,  9 Aug 2019 16:14:19 +0200
From:   Gerd Hoffmann <kraxel@...hat.com>
To:     dri-devel@...ts.freedesktop.org
Cc:     László Érsek <lersek@...hat.com>,
        Gerd Hoffmann <kraxel@...hat.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        virtualization@...ts.linux-foundation.org (open list:VIRTIO GPU DRIVER),
        linux-kernel@...r.kernel.org (open list)
Subject: [PATCH v2] drm/virtio: use virtio_max_dma_size

We must make sure our scatterlist segments are not too big, otherwise
we might see swiotlb failures (happens with sev, also reproducable with
swiotlb=force).

Suggested-by: Laszlo Ersek <lersek@...hat.com>
Signed-off-by: Gerd Hoffmann <kraxel@...hat.com>
---
 drivers/gpu/drm/virtio/virtgpu_object.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/virtio/virtgpu_object.c b/drivers/gpu/drm/virtio/virtgpu_object.c
index b2da31310d24..6e44568813dd 100644
--- a/drivers/gpu/drm/virtio/virtgpu_object.c
+++ b/drivers/gpu/drm/virtio/virtgpu_object.c
@@ -204,6 +204,7 @@ int virtio_gpu_object_get_sg_table(struct virtio_gpu_device *qdev,
 		.interruptible = false,
 		.no_wait_gpu = false
 	};
+	unsigned max_segment;
 
 	/* wtf swapping */
 	if (bo->pages)
@@ -215,8 +216,13 @@ int virtio_gpu_object_get_sg_table(struct virtio_gpu_device *qdev,
 	if (!bo->pages)
 		goto out;
 
-	ret = sg_alloc_table_from_pages(bo->pages, pages, nr_pages, 0,
-					nr_pages << PAGE_SHIFT, GFP_KERNEL);
+	max_segment = virtio_max_dma_size(qdev->vdev);
+	max_segment &= ~(size_t)(PAGE_SIZE - 1);
+	if (max_segment > SCATTERLIST_MAX_SEGMENT)
+		max_segment = SCATTERLIST_MAX_SEGMENT;
+	ret = __sg_alloc_table_from_pages(bo->pages, pages, nr_pages, 0,
+					  nr_pages << PAGE_SHIFT,
+					  max_segment, GFP_KERNEL);
 	if (ret)
 		goto out;
 	return 0;
-- 
2.18.1