Re: [PATCH v2 02/10] KVM: arm/arm64: vgic-its: Always allow clearing GITS_CREADR/CWRITER

Christoffer Dall
2017-10-13T17:54:42Z

On Fri, Oct 13, 2017 at 01:54:34PM +0200, Auger Eric wrote:
> Hi Christoffer,
> On 13/10/2017 13:44, Christoffer Dall wrote:
> > On Fri, Oct 06, 2017 at 05:29:02PM +0200, Auger Eric wrote:
> >> Hi,
> >>
> >> On 06/10/2017 16:37, Andre Przywara wrote:
> >>> Hi,
> >>>
> >>> On 27/09/17 14:28, Eric Auger wrote:
> >>>> If the GITS_CBASER Size field is 0, which can correspond to a
> >>>> reset value, the userspace fails to set the GITS_CREADR/CWRITER
> >>>> offsets to 0. This failure is not justified.
> >>>>
> >>>> Let's allow this setting which can also correspond to a reset value.
> >>>
> >>> But the GITS_CBASER size field has a +1 encoding, so can never be 0, if
> >>> I understand the manual (and ITS_CMD_BUFFER_SIZE) correctly.
> >> Oh OK, you're. I missed that. I would have sworn I've seen that failure
> >> but I must have misinterpreted it.
> >>
> >
> > What is CWRITER is written to a brand new ITS before the CBASER is
> > written?
> >
> > I don't see us initializing the cbaser field anywhere?
> in vgic_its_create() its is allocated with kzalloc so its->cbaser is
> initialized at this moment.
>

Right, so it can be 0, and we still need your patch, contrary to Andre's
comment. Am I missing something?

Thanks,
-Christoffer