From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:54426) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UhGw0-0002Bv-Fv for qemu-devel@nongnu.org; Tue, 28 May 2013 06:15:18 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1UhGvz-0004fc-3c for qemu-devel@nongnu.org; Tue, 28 May 2013 06:15:16 -0400 Received: from mx1.redhat.com ([209.132.183.28]:10823) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UhGvy-0004fR-RC for qemu-devel@nongnu.org; Tue, 28 May 2013 06:15:15 -0400 Message-ID: <51A483A3.3000703@redhat.com> Date: Tue, 28 May 2013 12:14:59 +0200 From: Paolo Bonzini MIME-Version: 1.0 References: <20130528101115.GA29353@redhat.com> In-Reply-To: <20130528101115.GA29353@redhat.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH RFC] virtio-pci: fix LE host/BE guest capacity for blk List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Michael S. Tsirkin" Cc: Peter Maydell , Anthony Liguori , agraf@suse.de, qemu-devel@nongnu.org, blauwirbel@gmail.com, KONRAD Frederic Il 28/05/2013 12:11, Michael S. Tsirkin ha scritto: > When a BE guest reads capacity from an LE host virtio-blk device or vice > versa, it will get the dwords of the qword field swapped. > As virtio-blk is the only one with such a quirk, > and as non-pci transports don't do byte-swaps at all, > solve this with a bit of device-specific hackery in > virtio-pci. > > Signed-off-by: Michael S. Tsirkin > --- > > I don't seem to be able to boot any big-endian > guests ATM, so this is only compile-tested - sending > this out for early feedback/flames. > Testing reports also wellcome! > > hw/virtio/virtio-pci.c | 9 +++++++++ > 1 file changed, 9 insertions(+) > > diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c > index 9668b2b..0e9ae4c 100644 > --- a/hw/virtio/virtio-pci.c > +++ b/hw/virtio/virtio-pci.c > @@ -411,6 +411,15 @@ static uint64_t virtio_pci_config_read(void *opaque, hwaddr addr, > } > break; > case 4: > + /* Most devices don't have 64 bit config fields. > + * Block is an exception: first 8 bytes include > + * a 64 bit capacity field. > + */ > + if (virtio_is_big_endian() != defined(HOST_WORDS_BIGENDIAN) && I thought think this is not valid C? Paolo > + proxy->vdev->dev_id == VIRTIO_ID_BLOCK && addr < 8) { > + /* Swap first two words */ > + addr ^= 0x4; > + } > val = virtio_config_readl(proxy->vdev, addr); > if (virtio_is_big_endian()) { > val = bswap32(val); >