Re: [Qemu-devel] [RFC PATCH v2 7/7] vfio/pci: Find and expose Intel IGD OpRegion

[Alex Williamson]

On Wed, 2016-02-03 at 10:29 +0100, Gerd Hoffmann wrote:
> On Di, 2016-02-02 at 13:09 -0700, Alex Williamson wrote:
> > This is provided via a device specific region, look for it on Intel
> > VGA class devices.  Our default mechanism to expose this to the BIOS
> > is via fw_cfg where it's expected that the BIOS will copy the data
> > into a reserved RAM area and update the ASL Storage register to
> > reference the GPA of that buffer.
> 
> >   We also support directly mapping
> > the OpRegion through to the host in response to the ASL Storage
> > register write, which makes the data "live" and potentially provides
> > write access should the underlying vfio region support writes.
> 
> This should better be splitted into a separate patch.

Ok.  Perhaps I'll drop it for now and make the kernel-level vfio code
expose the OpRegion as read-only as a start.  It's easy enough to dig
out of the mail archives and add back later if we want.

> > This
> > option is automatically enabled if we somehow don't support fw_cfg (is
> > this a good idea?).
> 
> I think this can't happen.  And even in case it can: we have bigger
> problems than the opregion then.

A few of the other fw_cfg_find() users seem to handle the error case,
which is why I ask.  Thanks,

Alex