Re: [Qemu-devel] [PATCH RFC v6 05/20] virtio: support more feature bits

[Thomas Huth]

 Hi,

On Thu, 29 Jan 2015 11:11:32 +1100
David Gibson <address@hidden> wrote:

> On Wed, Jan 28, 2015 at 04:59:45PM +0100, Cornelia Huck wrote:
> > On Thu, 22 Jan 2015 12:43:43 +1100
> > David Gibson <address@hidden> wrote:
> > 
> > > On Thu, Dec 11, 2014 at 02:25:07PM +0100, Cornelia Huck wrote:
> > > > With virtio-1, we support more than 32 feature bits. Let's extend both
> > > > host and guest features to 64, which should suffice for a while.
> > > > 
> > > > vhost and migration have been ignored for now.
> > > 
> > > [snip]
> > > 
> > > > diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
> > > > index f6c0379..08141c7 100644
> > > > --- a/include/hw/virtio/virtio.h
> > > > +++ b/include/hw/virtio/virtio.h
> > > > @@ -55,6 +55,12 @@
> > > >  /* A guest should never accept this.  It implies negotiation is 
> > > > broken. */
> > > >  #define VIRTIO_F_BAD_FEATURE           30
> > > >  
> > > > +/* v1.0 compliant. */
> > > > +#define VIRTIO_F_VERSION_1              32
> > > 
> > > This is already in the kernel header, isn't it?
> 
> > 
> > Yes. But nearly all files include this header but not the kernel
> > header.
> 
> Can't you change that?  Or this file include the kernel header?
 
AFAIK non-KVM code should never try to include one of the Linux headers
to avoid breaking on non-Linux platforms (for example <linux/types.h> is
not available on OS X, see http://patchwork.ozlabs.org/patch/424655/ ).
So it's a little bit ugly to define these things twice, but it seems
the only way to stay portable.

 Thomas

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