From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Kiszka Subject: Re: [PATCH v4 0/4] virtio: Clean up scatterlists and use the DMA API Date: Tue, 28 Jul 2015 15:11:40 +0200 Message-ID: <55B77F8C.7010804@siemens.com> References: <55B73A49.9050206@redhat.com> <1438078345.7562.133.camel@kernel.crashing.org> <55B7799C.3060908@redhat.com> <20150728160358-mutt-send-email-mst@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20150728160358-mutt-send-email-mst@redhat.com> 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 List-Archive: List-Post: To: "Michael S. Tsirkin" , Paolo Bonzini Cc: "linux-s390@vger.kernel.org" , xen-devel , Konrad Rzeszutek Wilk , Benjamin Herrenschmidt , Andy Lutomirski , Christian Borntraeger , "linux390@de.ibm.com" , Linux Virtualization List-ID: On 2015-07-28 15:06, Michael S. Tsirkin wrote: > On Tue, Jul 28, 2015 at 02:46:20PM +0200, Paolo Bonzini wrote: >> >> >> On 28/07/2015 12:12, Benjamin Herrenschmidt wrote: >>>>> That is an experimental feature (it's x-iommu), so it can change. >>>>> >>>>> The plan was: >>>>> >>>>> - for PPC, virtio never honors IOMMU >>>>> >>>>> - for non-PPC, either have virtio always honor IOMMU, or enforce that >>>>> virtio is not under IOMMU. >>>>> >>> I dislike having PPC special cased. >>> >>> In fact, today x86 guests also assume that virtio bypasses IOMMU I >>> believe. In fact *all* guests do. >> >> This doesn't matter much, since the only guests that implement an IOMMU >> in QEMU are (afaik) PPC and x86, and x86 does not yet promise any kind >> of stability. > > Hmm I think Jan (cc) said it was already used out there. Yes, no known issues with vt-d emulation for almost a year now. Error reporting could be improved, and interrupt remapping is still missing, but those are minor issues in this context. In my testing setups, I also have virtio devices in use, passed through to an L2 guest, but only in 1:1 mapping so that their broken IOMMU support causes no practical problems. Jan -- Siemens AG, Corporate Technology, CT RTC ITP SES-DE Corporate Competence Center Embedded Linux