From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wei Liu Subject: Re: [Xen-devel] [PATCH v5 09/10] vring: Use the DMA API on Xen Date: Mon, 1 Feb 2016 21:24:57 +0000 Message-ID: <20160201212457.GA9915@citrix.com> References: <64e979cc139c5e6a9bbfae9f1bc5e6693d91bea9.1454034075.git.luto@kernel.org> <56AB4053.4070007@citrix.com> <20160131220601-mutt-send-email-mst@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <20160131220601-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" Cc: linux-s390 , Joerg Roedel , wei.liu2@citrix.com, KVM , Stefano Stabellini , Benjamin Herrenschmidt , Sebastian Ott , "linux-kernel@vger.kernel.org" , Linux Virtualization , Christian Borntraeger , Martin Schwidefsky , Christoph Hellwig , David Vrabel , Andy Lutomirski , xen-devel@lists.xenproject.org, sparclinux@vger.kernel.org, Paolo Bonzini , David Woodhouse , "David S. Miller" List-ID: On Sun, Jan 31, 2016 at 10:09:07PM +0200, Michael S. Tsirkin wrote: > On Fri, Jan 29, 2016 at 10:34:59AM +0000, David Vrabel wrote: > > On 29/01/16 02:31, Andy Lutomirski wrote: > > > Signed-off-by: Andy Lutomirski > > > --- > > > drivers/virtio/virtio_ring.c | 12 ++++++++++++ > > > 1 file changed, 12 insertions(+) > > > > > > diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c > > > index c169c6444637..305c05cc249a 100644 > > > --- a/drivers/virtio/virtio_ring.c > > > +++ b/drivers/virtio/virtio_ring.c > > > @@ -47,6 +47,18 @@ > > > > > > static bool vring_use_dma_api(void) > > > { > > > +#if defined(CONFIG_X86) && defined(CONFIG_XEN) > > > + /* > > > + * In theory, it's possible to have a buggy QEMU-supposed > > > + * emulated Q35 IOMMU and Xen enabled at the same time. On > > > + * such a configuration, virtio has never worked and will > > > + * not work without an even larger kludge. Instead, enable > > > + * the DMA API if we're a Xen guest, which at least allows > > > + * all of the sensible Xen configurations to work correctly. > > > + */ > > > + return static_cpu_has(X86_FEATURE_XENPV); > > > > You want: > > > > if (xen_domain()) > > return true; > > > > Without the #if so we use the DMA API for all types of Xen guest on all > > architectures. > > > > David > > I doubt HVM domains can have virtio devices. > Yes, they can. When virtio-pci is used virtio device is just yet another pci device emulated by QEMU. Wei. > -- > MST > > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.xen.org > http://lists.xen.org/xen-devel