Re: [Qemu-devel] [PATCH v3 01/39] virtio-pci: get config on init

[Anthony Liguori]

On 08/08/2011 07:56 AM, Michael S. Tsirkin wrote:
> On Mon, Aug 08, 2011 at 07:45:19AM -0500, Anthony Liguori wrote:
> > On 08/08/2011 05:36 AM, Michael S. Tsirkin wrote:
> > > > Thinking more closely, I don't think this right.
> > > >
> > > > Updating on map ensured that the config was refreshed after each
> > > > time the bar was mapped.  In the very least, the config needs to be
> > > > refreshed during reset because the guest may write to the guest
> > > > space which should get cleared after reset.
> > > >
> > > > Regards,
> > > >
> > > > Anthony Liguori
> > >
> > > Not sure I understand. Which register, for example,
> > > do you have in mind?
> > > Could you clarify please?
> >
> > Actually, you never need to call config_get() AFAICT.  It's called
> > in every read/write access.
>
> Every read, yes. But every write? Are you sure?

Yeah, not on write, but I think this is a bug.  get_config() should be 
called before doing the memcpy() in order to have a proper RMW.

Regards,

Anthony Liguori

> >   So I think the code you changed is
> > extraneous now.
> >
> > Regards,
> >
> > Anthony Liguori