From mboxrd@z Thu Jan 1 00:00:00 1970 From: Greg Kurz Subject: Re: [Qemu-devel] [PATCH RFC 05/11] virtio: introduce legacy virtio devices Date: Thu, 30 Oct 2014 23:29:50 +0100 Message-ID: <20141030232950.00ee96e4@bahia.local> References: <1412692807-12398-1-git-send-email-cornelia.huck@de.ibm.com> <1412692807-12398-6-git-send-email-cornelia.huck@de.ibm.com> <20141028164018.29d73d9f@bahia.local> <20141030190201.41e8940d.cornelia.huck@de.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: thuth@linux.vnet.ibm.com, qemu-devel@nongnu.org, kvm@vger.kernel.org, virtualization@lists.linux-foundation.org To: Cornelia Huck Return-path: In-Reply-To: <20141030190201.41e8940d.cornelia.huck@de.ibm.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-Id: kvm.vger.kernel.org On Thu, 30 Oct 2014 19:02:01 +0100 Cornelia Huck wrote: > On Tue, 28 Oct 2014 16:40:18 +0100 > Greg Kurz wrote: > > > On Tue, 7 Oct 2014 16:40:01 +0200 > > Cornelia Huck wrote: > > > > > Introduce a helper function to indicate whether a virtio device is > > > operating in legacy or virtio standard mode. > > > > > > It may be used to make decisions about the endianess of virtio accesses > > > and other virtio-1 specific changes, enabling us to support transitional > > > devices. > > > > > > Reviewed-by: Thomas Huth > > > Signed-off-by: Cornelia Huck > > > --- > > > hw/virtio/virtio.c | 6 +++++- > > > include/hw/virtio/virtio-access.h | 4 ++++ > > > include/hw/virtio/virtio.h | 13 +++++++++++-- > > > 3 files changed, 20 insertions(+), 3 deletions(-) > > > > > > diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c > > > index 7aaa953..e6ae3a0 100644 > > > --- a/hw/virtio/virtio.c > > > +++ b/hw/virtio/virtio.c > > > @@ -883,7 +883,11 @@ static bool virtio_device_endian_needed(void *opaque) > > > VirtIODevice *vdev = opaque; > > > > > > assert(vdev->device_endian != VIRTIO_DEVICE_ENDIAN_UNKNOWN); > > > - return vdev->device_endian != virtio_default_endian(); > > > + if (virtio_device_is_legacy(vdev)) { > > > + return vdev->device_endian != virtio_default_endian(); > > > + } > > > + /* Devices conforming to VIRTIO 1.0 or later are always LE. */ > > > + return vdev->device_endian != VIRTIO_DEVICE_ENDIAN_LITTLE; > > > } > > > > > > > Shouldn't we have some code doing the following somewhere ? > > > > if (!virtio_device_is_legacy(vdev)) { > > vdev->device_endian = VIRTIO_DEVICE_ENDIAN_LITTLE; > > } > > > > also, since virtio-1 is LE only, do we expect device_endian to > > be different from VIRTIO_DEVICE_ENDIAN_LITTLE ? > > device_endian should not depend on whether the device is legacy or not. > virtio_is_big_endian always returns false for virtio-1 devices, though. Sorry, I had missed the virtio_is_big_endian() change: it that makes device_endian a legacy virtio only matter. So why would we care to migrate the endian subsection when we have a virtio-1 device ? Shouldn't virtio_device_endian_needed() return false for virtio-1 ? -- Greg