Re: [PATCH v3] hw/audio/virtio-snd: Use device endianness instead of target one

[Michael S. Tsirkin]

On Mon, Apr 22, 2024 at 11:07:21PM +0200, Philippe Mathieu-Daudé wrote:
> On 22/4/24 23:02, Michael S. Tsirkin wrote:
> > On Mon, Apr 22, 2024 at 04:20:56PM +0200, Philippe Mathieu-Daudé wrote:
> > > Since VirtIO devices can change endianness at runtime,
> > > we need to use the device endianness, not the target
> > > one.
> > > 
> > > Cc: qemu-stable@nongnu.org
> > > Fixes: eb9ad377bb ("virtio-sound: handle control messages and streams")
> > > Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
> > 
> > 
> > 
> > This is all completely bogus. Virtio SND is from Virtio 1.0 only.
> > It is unconditionally little endian.
> 
> Oh, then the fix is as simple as:
> 
>  -    as->endianness = target_words_bigendian() ? 1 : 0;
>  +    as->endianness = 0; /* VIRTIO 1.0: always LE. */

Makes sense. Pls clarify in commit log whether the incorrect
value leads to any failures or this was found by code review.

> > If it's not it's a guest bug pls just fix it there.
> > 
> > 
> > > ---
> > > v2: Use virtio_is_big_endian()
> > > v3: Remove "hw/core/cpu.h
> > > ---
> > >   hw/audio/virtio-snd.c | 9 +++++----
> > >   1 file changed, 5 insertions(+), 4 deletions(-)
> > > 
> > > diff --git a/hw/audio/virtio-snd.c b/hw/audio/virtio-snd.c
> > > index c80b58bf5d..939cd78026 100644
> > > --- a/hw/audio/virtio-snd.c
> > > +++ b/hw/audio/virtio-snd.c
> > > @@ -24,7 +24,6 @@
> > >   #include "trace.h"
> > >   #include "qapi/error.h"
> > >   #include "hw/audio/virtio-snd.h"
> > > -#include "hw/core/cpu.h"
> > >   #define VIRTIO_SOUND_VM_VERSION 1
> > >   #define VIRTIO_SOUND_JACK_DEFAULT 0
> > > @@ -395,13 +394,15 @@ static uint32_t virtio_snd_get_qemu_freq(uint32_t 
> > > rate)
> > >    * Get QEMU Audiosystem compatible audsettings from virtio based pcm 
> > > stream
> > >    * params.
> > >    */
> > > -static void virtio_snd_get_qemu_audsettings(audsettings *as,
> > > +static void virtio_snd_get_qemu_audsettings(VirtIOSound *s, audsettings 
> > > *as,
> > >                                               virtio_snd_pcm_set_params 
> > > *params)
> > >   {
> > > +    VirtIODevice *vdev = VIRTIO_DEVICE(s);
> > > +
> > >       as->nchannels = MIN(AUDIO_MAX_CHANNELS, params->channels);
> > >       as->fmt = virtio_snd_get_qemu_format(params->format);
> > >       as->freq = virtio_snd_get_qemu_freq(params->rate);
> > > -    as->endianness = target_words_bigendian() ? 1 : 0;
> > > +    as->endianness = virtio_is_big_endian(vdev) ? 1 : 0;
> > >   }
> > >   /*
> > > @@ -464,7 +465,7 @@ static uint32_t virtio_snd_pcm_prepare(VirtIOSound 
> > > *s, uint32_t stream_id)
> > >           s->pcm->streams[stream_id] = stream;
> > >       }
> > > -    virtio_snd_get_qemu_audsettings(&as, params);
> > > +    virtio_snd_get_qemu_audsettings(s, &as, params);
> > >       stream->info.direction = stream_id < s->snd_conf.streams / 2 +
> > >           (s->snd_conf.streams & 1) ? VIRTIO_SND_D_OUTPUT : 
> > > VIRTIO_SND_D_INPUT;
> > >       stream->info.hdr.hda_fn_nid = VIRTIO_SOUND_HDA_FN_NID;
> > > -- 
> > > 2.41.0
> >