From mboxrd@z Thu Jan 1 00:00:00 1970 From: Joerg Roedel Subject: [PATCH 0/3] Fix virtio-blk issue with SWIOTLB Date: Thu, 10 Jan 2019 14:44:30 +0100 Message-ID: <20190110134433.15672-1-joro@8bytes.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: "Michael S . Tsirkin" , Jason Wang , Konrad Rzeszutek Wilk Cc: Jens Axboe , brijesh.singh-5C7GfCeVMHo@public.gmane.org, jon.grimm-5C7GfCeVMHo@public.gmane.org, jfehlig-IBi9RG/b67k@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-block-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, virtualization-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, hch-jcswGhMUV9g@public.gmane.org List-Id: iommu@lists.linux-foundation.org Hi, there is a problem with virtio-blk driven devices when virtio-ring uses SWIOTLB through the DMA-API. This happens for example in AMD-SEV enabled guests, where the guest RAM is mostly encrypted and all emulated DMA has to happen to/from the SWIOTLB aperture. The problem is a limitation of the SWIOTLB implementation, which does not support allocations larger than 256kb. When the virtio-blk driver tries to read/write a block larger than that, the allocation of the dma-handle fails and an IO error is reported. This patch-set adds a check to the virtio-code whether it might be using SWIOTLB bounce buffering and limits the maximum segment size in the virtio-blk driver in this case, so that it doesn't try to do larger reads/writes. Please review. Thanks, Joerg Joerg Roedel (3): swiotlb: Export maximum allocation size virtio: Introduce virtio_max_dma_size() virtio-blk: Consider virtio_max_dma_size() for maximum segment size drivers/block/virtio_blk.c | 10 ++++++---- drivers/virtio/virtio_ring.c | 11 +++++++++++ include/linux/swiotlb.h | 12 ++++++++++++ include/linux/virtio.h | 2 ++ 4 files changed, 31 insertions(+), 4 deletions(-) -- 2.17.1