From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Subject: Re: [PATCH 0/3] Fix virtio-blk issue with SWIOTLB Date: Mon, 14 Jan 2019 10:50:02 +0100 Message-ID: <20190114095002.GA29874@lst.de> References: <20190110134433.15672-1-joro@8bytes.org> <5ae1341e-62ec-0478-552b-259eabf9fb17@redhat.com> <20190111091502.GC5825@8bytes.org> <38bcbd46-674c-348a-cbd6-66bd431e986a@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Return-path: Content-Disposition: inline In-Reply-To: <38bcbd46-674c-348a-cbd6-66bd431e986a@redhat.com> Sender: linux-kernel-owner@vger.kernel.org To: Jason Wang Cc: Joerg Roedel , "Michael S . Tsirkin" , Konrad Rzeszutek Wilk , Jens Axboe , virtualization@lists.linux-foundation.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org, jfehlig@suse.com, jon.grimm@amd.com, brijesh.singh@amd.com, hch@lst.de List-Id: iommu@lists.linux-foundation.org On Mon, Jan 14, 2019 at 05:41:56PM +0800, Jason Wang wrote: > > On 2019/1/11 下午5:15, Joerg Roedel wrote: >> On Fri, Jan 11, 2019 at 11:29:31AM +0800, Jason Wang wrote: >>> Just wonder if my understanding is correct IOMMU_PLATFORM must be set for >>> all virtio devices under AMD-SEV guests? >> Yes, that is correct. Emulated DMA can only happen on the SWIOTLB >> aperture, because that memory is not encrypted. The guest bounces the >> data then to its encrypted memory. >> >> Regards, >> >> Joerg > > > Thanks, have you tested vhost-net in this case. I suspect it may not work Which brings me back to my pet pevee that we need to take actions that virtio uses the proper dma mapping API by default with quirks for legacy cases. The magic bypass it uses is just causing problems over problems.