Re: [Xen-devel] [PATCH V2] arch: arm: vgic-v3: fix GICD_ISACTIVER range

[Jürgen Groß <jgross@xxxxxxxx>]

On 27.11.19 01:01, Julien Grall wrote:
> Hi,
>
> On 26/11/2019 23:17, Stefano Stabellini wrote:
> > On Tue, 26 Nov 2019, Julien Grall wrote:
> > > Hi,
> > >
> > > On 26/11/2019 20:43, Stefano Stabellini wrote:
> > > > + Juergen
> > > >
> > > > I missed that you weren't in CC to the original patch, sorry.
> > > > I think this patch should go in, as otherwise Linux 5.4 could run into
> > > > problems. It is also a pretty straightforward 4 lines patch.
> > > 5.5 (or 5.6) is not going to run on Xen for other reasons (still in the
> > > vGIC)... So I would not view this as critical.
> > 5.5 is not out yet, in fact, the dev window has just opened. Isn't your
> > statement a bit premature?
> The GICv4.1 work [1] is going to prevent Linux booting on all current 
> versions of Xen. While I can't confirm this is going to be merged in 
> 5.5, I can tell you this will break.
> > In any case, even if potential future Linux releases could have other
> > additional issues, I don't think it should change our current view on
> > this specific issue which affects 5.4, just released.
> The patch is definitely not as straightforward as you may think. Please 
> refer to the discussion we had on the first version. I voiced concern 
> about this approach and gave point what could go wrong with happen.
> This patch may be better than the current state (i.e crashing), but this 
> wasn't tested enough to confirm this is the correct things to do and no 
> other bug will appear (I don't believe reading I*ACTIVER was ever tested 
> before).
> It is an annoying bug, but this is only affecting 5.4 which has just 
> been released. It feels to me this is a fairly risky choice to merge it 
> qutie late in the release without a good graps of the problem (see above).
> So I would definitly, prefer if this patch is getting through backport 
> once we get more testing.
> We can still document the bug in the release note and point people to 
> the patch.
> Anyway, this is Juergen choice here. But at least now he has the full 
> picture...
> Cheers,
>
> [1] https://lwn.net/Articles/800494/
Thanks, Julien, for sharing your opinion.

With that statement I'd like to defer this patch to 4.14.


Juergen

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