Re: (subset) [PATCH 1/3] KVM: arm64: vgic: Fix IIDR revision field extracted from wrong value

[David Woodhouse]

On Fri, 2026-04-24 at 13:24 +0100, David Woodhouse wrote:
> On Fri, 2026-04-24 at 12:07 +0100, Marc Zyngier wrote:
> > On Tue, 07 Apr 2026 21:27:02 +0100, David Woodhouse wrote:
> > > The uaccess write handlers for GICD_IIDR in both GICv2 and GICv3
> > > extract the revision field from 'reg' (the current IIDR value read back
> > > from the emulated distributor) instead of 'val' (the value userspace is
> > > trying to write). This means userspace can never actually change the
> > > implementation revision — the extracted value is always the current one.
> > > 
> > > Fix the FIELD_GET to use 'val' so that userspace can select a different
> > > revision for migration compatibility.
> > > 
> > > [...]
> > 
> > Applied to fixes, thanks!
> > 
> > [1/3] KVM: arm64: vgic: Fix IIDR revision field extracted from wrong value
> >       commit: a0e6ae45af17e8b27958830595799c702ffbab8d
> 
> There was a v2 of this series which also cleaned up the weird
> inconsistency of the IIDR value with the actual behaviour, and which
> fixed the fact that it's currently not possible to maintain guest
> compatibility when upgrading from a pre-d53c2c29ae0d kernel to a new
> one — despite the fact that that kind of compatibility is *precisely*
> what the revision field in the IIDR is designed for.
> 
> https://lore.kernel.org/all/20260408113256.2095505-1-dwmw2@xxxxxxxxxxxxx/

Is there a reason the rest of these fixes didn't make 7.1?

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