From mboxrd@z Thu Jan 1 00:00:00 1970 From: Joerg Roedel Subject: [PATCH 4/5] virtio: Introduce virtio_max_dma_size() Date: Thu, 31 Jan 2019 17:34:02 +0100 Message-ID: <20190131163403.11363-5-joro__40821.6452038445$1548966798$gmane$org@8bytes.org> References: <20190131163403.11363-1-joro@8bytes.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20190131163403.11363-1-joro@8bytes.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org To: "Michael S . Tsirkin" , Jason Wang , Konrad Rzeszutek Wilk , Christoph Hellwig Cc: Jens Axboe , Thomas.Lendacky@amd.com, jroedel@suse.de, brijesh.singh@amd.com, joro@8bytes.org, jon.grimm@amd.com, jfehlig@suse.com, linux-kernel@vger.kernel.org, linux-block@vger.kernel.org, iommu@lists.linux-foundation.org, virtualization@lists.linux-foundation.org List-Id: virtualization@lists.linuxfoundation.org From: Joerg Roedel This function returns the maximum segment size for a single dma transaction of a virtio device. The possible limit comes from the SWIOTLB implementation in the Linux kernel, that has an upper limit of (currently) 256kb of contiguous memory it can map. Other DMA-API implementations might also have limits. Use the new dma_max_mapping_size() function to determine the maximum mapping size when DMA-API is in use for virtio. Reviewed-by: Konrad Rzeszutek Wilk Reviewed-by: Christoph Hellwig Signed-off-by: Joerg Roedel --- drivers/virtio/virtio_ring.c | 11 +++++++++++ include/linux/virtio.h | 2 ++ 2 files changed, 13 insertions(+) diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c index cd7e755484e3..8a31c6862b2b 100644 --- a/drivers/virtio/virtio_ring.c +++ b/drivers/virtio/virtio_ring.c @@ -266,6 +266,17 @@ static bool vring_use_dma_api(struct virtio_device *vdev) return false; } +size_t virtio_max_dma_size(struct virtio_device *vdev) +{ + size_t max_segment_size = SIZE_MAX; + + if (vring_use_dma_api(vdev)) + max_segment_size = dma_max_mapping_size(&vdev->dev); + + return max_segment_size; +} +EXPORT_SYMBOL_GPL(virtio_max_dma_size); + static void *vring_alloc_queue(struct virtio_device *vdev, size_t size, dma_addr_t *dma_handle, gfp_t flag) { diff --git a/include/linux/virtio.h b/include/linux/virtio.h index fa1b5da2804e..673fe3ef3607 100644 --- a/include/linux/virtio.h +++ b/include/linux/virtio.h @@ -157,6 +157,8 @@ int virtio_device_freeze(struct virtio_device *dev); int virtio_device_restore(struct virtio_device *dev); #endif +size_t virtio_max_dma_size(struct virtio_device *vdev); + #define virtio_device_for_each_vq(vdev, vq) \ list_for_each_entry(vq, &vdev->vqs, list) -- 2.17.1