Re: [KVM PATCH v8 3/3] KVM: add iosignalfd support

[Avi Kivity]

On 06/23/2009 01:48 PM, Michael S. Tsirkin wrote:
> On Tue, Jun 23, 2009 at 12:57:53PM +0300, Avi Kivity wrote:
>    
> > On 06/23/2009 11:56 AM, Michael S. Tsirkin wrote:
> >      
> > > On Thu, Jun 18, 2009 at 08:30:46PM -0400, Gregory Haskins wrote:
> > >
> > >        
> > > > +static int
> > > > +iosignalfd_group_in_range(struct kvm_io_device *this, gpa_t addr, int len,
> > > > +			  int is_write)
> > > > +{
> > > > +	struct _iosignalfd_group *p = to_group(this);
> > > > +
> > > > +	return ((addr>= p->addr&&   (addr<   p->addr + p->length)));
> > > > +}
> > > >
> > > >          
> > > I think I see a problem here. For virtio, we do not necessarily want all
> > > virtqueues for a device to live in kernel: there might be control
> > > virtqueues that we want to leave in userspace. Since this claims all
> > > writes to a specific address, the signal never makes it to userspace.
> > >
> > >        
> > Userspace could create an eventfd for this control queue and wait for it
> > to fire.
> >      
>
> What if guest writes an unexpected value there?
> The value it simply lost ... that's not very elegant.
>    

True, it's better to have a lossless interface.

--
error compiling committee.c: too many arguments to function

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