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Re: [Qemu-devel] [PATCH 01/15] s390x: fix virtio feature bitmap
From: |
Aurelien Jarno |
Subject: |
Re: [Qemu-devel] [PATCH 01/15] s390x: fix virtio feature bitmap |
Date: |
Sun, 10 Apr 2011 22:06:53 +0200 |
User-agent: |
Mutt/1.5.20 (2009-06-14) |
On Sun, Apr 10, 2011 at 09:26:26PM +0200, Alexander Graf wrote:
>
> On 10.04.2011, at 21:25, Aurelien Jarno wrote:
>
> > On Mon, Apr 04, 2011 at 04:32:10PM +0200, Alexander Graf wrote:
> >> The feature bitmap in the s390 virtio machine is little endian. To
> >> address for that, we need to bswap the values after reading them out.
> >>
> >> Signed-off-by: Alexander Graf <address@hidden>
> >> ---
> >> hw/s390-virtio-bus.c | 4 ++--
> >> 1 files changed, 2 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/hw/s390-virtio-bus.c b/hw/s390-virtio-bus.c
> >> index 58af164..60e0135 100644
> >> --- a/hw/s390-virtio-bus.c
> >> +++ b/hw/s390-virtio-bus.c
> >> @@ -223,7 +223,7 @@ void s390_virtio_device_sync(VirtIOS390Device *dev)
> >> cur_offs += num_vq * VIRTIO_VQCONFIG_LEN;
> >>
> >> /* Sync feature bitmap */
> >> - stl_phys(cur_offs, dev->host_features);
> >> + stl_phys(cur_offs, bswap32(dev->host_features));
> >
> > Is bswap32 correct here for both big and little endian guests? I don't
> > really understand the reason why a bswap is needed here, especially
> > given that AFAIK this code was already used when using KVM.
>
> This is target specific code. The s390-virtio-bus is s390 specific. And yes,
> the code was also broken with KVM. That's how I first found it actually.
>
So in short, s390-virtio-bus is specific to big endian machines, but is
using little endian? That looks a bit weired. I guess it's probably to
late to change the specification anyway...
--
Aurelien Jarno GPG: 1024D/F1BCDB73
address@hidden http://www.aurel32.net
[Qemu-devel] [PATCH 15/15] tcg: use ext op for deposit, Alexander Graf, 2011/04/04
- Re: [Qemu-devel] [PATCH 15/15] tcg: use ext op for deposit, Aurelien Jarno, 2011/04/05
- Re: [Qemu-devel] [PATCH 15/15] tcg: use ext op for deposit, Alexander Graf, 2011/04/05
- Re: [Qemu-devel] [PATCH 15/15] tcg: use ext op for deposit, Aurelien Jarno, 2011/04/10
- Re: [Qemu-devel] [PATCH 15/15] tcg: use ext op for deposit, Alexander Graf, 2011/04/10
- Re: [Qemu-devel] [PATCH 15/15] tcg: use ext op for deposit, Aurelien Jarno, 2011/04/10
- Re: [Qemu-devel] [PATCH 15/15] tcg: use ext op for deposit, Alexander Graf, 2011/04/10
- Re: [Qemu-devel] [PATCH 15/15] tcg: use ext op for deposit, Aurelien Jarno, 2011/04/10