From mboxrd@z Thu Jan 1 00:00:00 1970 From: Will Deacon Subject: Re: [PATCH 3/3] virtio: fix endianness check for vhost support Date: Wed, 2 Mar 2016 01:27:54 +0000 Message-ID: <20160302012753.GF14022@arm.com> References: <1456850978-14091-1-git-send-email-andre.przywara@arm.com> <1456850978-14091-4-git-send-email-andre.przywara@arm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: Pekka Enberg , Sasha Levin , kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org, linux-kernel@vger.kernel.org To: Andre Przywara Return-path: Content-Disposition: inline In-Reply-To: <1456850978-14091-4-git-send-email-andre.przywara@arm.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu List-Id: kvm.vger.kernel.org On Tue, Mar 01, 2016 at 04:49:38PM +0000, Andre Przywara wrote: > Currently we deny any VHOST_* functionality if the architecture > supports guests with different endianness than the host. Most of the > time even on those architectures the endianness of guest and host are > the same, though, so we are denying the glory of VHOST needlessly. > Switch from compile time determination to a run time scheme, which > takes the actual endianness of the guest into account. > For this we change the semantics of VIRTIO_ENDIAN_HOST to return the > actual endianness of the host (the endianness of kvmtool at compile > time, really). The actual check in vhost_net now compares this against > the guest endianness. > This enables vhost support on ARM and ARM64. > > Signed-off-by: Andre Przywara > --- > include/kvm/virtio.h | 9 +++++++-- > virtio/net.c | 2 +- > 2 files changed, 8 insertions(+), 3 deletions(-) > > diff --git a/include/kvm/virtio.h b/include/kvm/virtio.h > index 768ee96..66530fd 100644 > --- a/include/kvm/virtio.h > +++ b/include/kvm/virtio.h > @@ -17,10 +17,15 @@ > #define VIRTIO_PCI_O_CONFIG 0 > #define VIRTIO_PCI_O_MSIX 1 > > -#define VIRTIO_ENDIAN_HOST 0 > #define VIRTIO_ENDIAN_LE (1 << 0) > #define VIRTIO_ENDIAN_BE (1 << 1) > > +#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__ > +#define VIRTIO_ENDIAN_HOST VIRTIO_ENDIAN_LE > +#else > +#define VIRTIO_ENDIAN_HOST VIRTIO_ENDIAN_BE > +#endif pci.h already uses __BYTE_ORDER and __LITTLE_ENDIAN, so we should at least be consistent here. Will