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Date: Mon, 1 Feb 2016 21:24:57 +0000 From: Wei Liu <wei.liu2@...rix.com> To: "Michael S. Tsirkin" <mst@...hat.com> CC: David Vrabel <david.vrabel@...rix.com>, linux-s390 <linux-s390@...r.kernel.org>, <sparclinux@...r.kernel.org>, Joerg Roedel <jroedel@...e.de>, KVM <kvm@...r.kernel.org>, Stefano Stabellini <stefano.stabellini@...citrix.com>, Benjamin Herrenschmidt <benh@...nel.crashing.org>, Sebastian Ott <sebott@...ux.vnet.ibm.com>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "Linux Virtualization" <virtualization@...ts.linux-foundation.org>, "Christian Borntraeger" <borntraeger@...ibm.com>, "David S. Miller" <davem@...emloft.net>, Andy Lutomirski <luto@...nel.org>, Paolo Bonzini <pbonzini@...hat.com>, Cornelia Huck <cornelia.huck@...ibm.com>, <xen-devel@...ts.xenproject.org>, David Woodhouse <dwmw2@...radead.org>, Christoph Hellwig <hch@....de>, Martin Schwidefsky <schwidefsky@...ibm.com>, <wei.liu2@...rix.com> Subject: Re: [Xen-devel] [PATCH v5 09/10] vring: Use the DMA API on Xen 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 <luto@...nel.org> > > > --- > > > 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@...ts.xen.org > http://lists.xen.org/xen-devel
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