From mboxrd@z Thu Jan 1 00:00:00 1970 From: Greg Kurz Subject: Re: [Qemu-devel] [PATCH RFC v3 05/12] virtio: introduce legacy virtio devices Date: Wed, 26 Nov 2014 19:46:38 +0100 Message-ID: <20141126194638.2e110e78@bahia.local> References: <1417022923-1654-1-git-send-email-cornelia.huck@de.ibm.com> <1417022923-1654-6-git-send-email-cornelia.huck@de.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: virtualization@lists.linux-foundation.org, qemu-devel@nongnu.org, kvm@vger.kernel.org, rusty@rustcorp.com.au, thuth@linux.vnet.ibm.com, mst@redhat.com To: Cornelia Huck Return-path: Received: from e06smtp10.uk.ibm.com ([195.75.94.106]:47383 "EHLO e06smtp10.uk.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750850AbaKZSqv (ORCPT ); Wed, 26 Nov 2014 13:46:51 -0500 Received: from /spool/local by e06smtp10.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Wed, 26 Nov 2014 18:46:49 -0000 Received: from b06cxnps3074.portsmouth.uk.ibm.com (d06relay09.portsmouth.uk.ibm.com [9.149.109.194]) by d06dlp03.portsmouth.uk.ibm.com (Postfix) with ESMTP id 9B28B1B08040 for ; Wed, 26 Nov 2014 18:47:01 +0000 (GMT) Received: from d06av10.portsmouth.uk.ibm.com (d06av10.portsmouth.uk.ibm.com [9.149.37.251]) by b06cxnps3074.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id sAQIkkvO5046712 for ; Wed, 26 Nov 2014 18:46:46 GMT Received: from d06av10.portsmouth.uk.ibm.com (localhost [127.0.0.1]) by d06av10.portsmouth.uk.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id sAQIkjrN003130 for ; Wed, 26 Nov 2014 11:46:46 -0700 In-Reply-To: <1417022923-1654-6-git-send-email-cornelia.huck@de.ibm.com> Sender: kvm-owner@vger.kernel.org List-ID: On Wed, 26 Nov 2014 18:28:36 +0100 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 2eb5d3c..4149f45 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; > } > Sorry but I still don't understand why we need to stream the device_endian subsection if we have a virtio-1 device... this field is only used on legacy device paths. Can you share an example where it is needed ? > static const VMStateDescription vmstate_virtio_device_endian = { > diff --git a/include/hw/virtio/virtio-access.h b/include/hw/virtio/virtio-access.h > index 46456fd..c123ee0 100644 > --- a/include/hw/virtio/virtio-access.h > +++ b/include/hw/virtio/virtio-access.h > @@ -19,6 +19,10 @@ > > static inline bool virtio_access_is_big_endian(VirtIODevice *vdev) > { > + if (!virtio_device_is_legacy(vdev)) { > + /* Devices conforming to VIRTIO 1.0 or later are always LE. */ > + return false; > + } > #if defined(TARGET_IS_BIENDIAN) > return virtio_is_big_endian(vdev); > #elif defined(TARGET_WORDS_BIGENDIAN) > diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h > index b408166..40e567c 100644 > --- a/include/hw/virtio/virtio.h > +++ b/include/hw/virtio/virtio.h > @@ -275,9 +275,18 @@ void virtio_queue_set_host_notifier_fd_handler(VirtQueue *vq, bool assign, > void virtio_queue_notify_vq(VirtQueue *vq); > void virtio_irq(VirtQueue *vq); > > +static inline bool virtio_device_is_legacy(VirtIODevice *vdev) > +{ > + return !(vdev->guest_features[1] & (1 << (VIRTIO_F_VERSION_1 - 32))); > +} > + > static inline bool virtio_is_big_endian(VirtIODevice *vdev) > { > - assert(vdev->device_endian != VIRTIO_DEVICE_ENDIAN_UNKNOWN); > - return vdev->device_endian == VIRTIO_DEVICE_ENDIAN_BIG; > + if (virtio_device_is_legacy(vdev)) { > + assert(vdev->device_endian != VIRTIO_DEVICE_ENDIAN_UNKNOWN); > + return vdev->device_endian == VIRTIO_DEVICE_ENDIAN_BIG; > + } > + /* Devices conforming to VIRTIO 1.0 or later are always LE. */ > + return false; > } > #endif