Re: [4.17] RE: [PATCH v2] xen/arm: p2m: fix pa_range_info for 52-bit pa range

[Julien Grall <julien@xxxxxxx>]

On 21/10/2022 02:42, Henry Wang wrote:
> Hi Julien and Xenia,
Hi Henry,


> > -----Original Message-----
> > From: Julien Grall <julien@xxxxxxx>
> > <Volodymyr_Babchuk@xxxxxxxx>; Henry Wang <Henry.Wang@xxxxxxx>
> > Subject: Re: [PATCH v2] xen/arm: p2m: fix pa_range_info for 52-bit pa range
> >
> > (+ Henry)
> >
> > Hi Xenia,
> >
> > On 19/10/2022 15:49, Xenia Ragiadakou wrote:
> > > Currently, the fields 'root_order' and 'sl0' of the pa_range_info for
> > > the 52-bit pa range have the values 3 and 3, respectively.
> > > This configuration does not match any of the valid root table configurations
> > > for 4KB granule and t0sz 12, described in ARM DDI 0487I.a D8.2.7.
> > >
> > > More specifically, according to ARM DDI 0487I.a D8.2.7, in order to support
> > > the 52-bit pa size with 4KB granule, the p2m root table needs to be
> > configured
> > > either as a single table at level -1 or as 16 concatenated tables at level 0.
> > > Since, currently there is not support for level -1, set the 'root_order' an
> > Typo: s/not/no/ (I can fix it while committing)
> >
> > > 'sl0' fields of the 52-bit pa_range_info according to the second approach.
> > >
> > > Note that the values of those fields are not used so far. This patch updates
> > > their values only for the sake of correctness.
> > >
> > > Fixes: 407b13a71e32 ("xen/arm: p2m don't fall over on FEAT_LPA enabled
> > hw")
> > > Signed-off-by: Xenia Ragiadakou <burzalodowa@xxxxxxxxx>
> > Reviewed-by: Julien Grall <jgrall@xxxxxxxxxx>
> >
> > Regarding 4.17, I am a bit split whether this should be included. On one
> > hand, it would be good to have the value correct (not that I expect
> > anymore to try using 52-bit on 4.17...). On the other hand, this is not
> > used so there is no bug (this could also be an argument to add it
> > because it is nearly risk free).
> >
> > If we don't include it, I will definitely add in my list of potential
> > backports.
> >
> > Henry, any thoughts?
> I am actually monitoring this patch for the same question that if
> we need this patch for 4.17.
>
> I see no reason to exclude this patch since (1) we want to make sure
> our code is correct (2) I am pretty sure we are not using 52 bit PA so
> as indicated by commit message this patch is just for correctness and
> no potential harm to include this patch in the release (probably even
> backporting this patch till the 52 bit PA was introduced?).
>
> So if you wouldn't mind committing this patch, you can of course have
> my:
Thanks for the feedback. I am happy to commit it. So...

> Release-acked-by: Henry Wang <Henry.Wang@xxxxxxx>
I have now done it with your tag added.

Cheers,

--
Julien Grall