Re: [PATCH 04/28] KVM: arm64: Drop __HCRX_EL2_* masks

[Marc Zyngier <maz@kernel.org>]

On Thu, 02 Jul 2026 19:34:49 +0100,
sashiko-bot@kernel.org wrote:
> 
> Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
> 
> Pre-existing issues:
> - [High] Unsanitized architectural RES0/RES1 bits in HCRX_EL2 allow nested guests to enable hidden hardware features and trigger CONSTRAINED UNPREDICTABLE behavior.
> --
> 
> commit c528765403e37bb993d380c50856d508033ad43a
> Author: Marc Zyngier <maz@kernel.org>
> 
> KVM: arm64: Drop __HCRX_EL2_* masks
> 
> This patch removes the legacy __HCRX_EL2_* masks and the manual RES1
> sanitization in get_reg_fixed_bits(). It intends to rely on existing
> auto-generated masks and boot-time checks to prevent unhandled bits from
> being exploited.
> 
> > diff --git a/arch/arm64/kvm/config.c b/arch/arm64/kvm/config.c
> > index 0622162b089e5..16d8148dc3f12 100644
> > --- a/arch/arm64/kvm/config.c
> > +++ b/arch/arm64/kvm/config.c
> [ ... ]
> > @@ -933,7 +933,7 @@ static const struct reg_bits_to_feat_map hcrx_feat_map[] = {
> >  };
> >  
> >  
> > -static const DECLARE_FEAT_MAP(hcrx_desc, __HCRX_EL2,
> > +static const DECLARE_FEAT_MAP(hcrx_desc, HCRX_EL2,
> >  			      hcrx_feat_map, FEAT_HCX);
> 
> [Severity: High]
> This is a pre-existing issue, but hcrx_feat_map lacks FORCE_RES0 and
> FORCE_RES1 declarations. Unlike other system register maps, this means
> compute_reg_resx_bits() will omit the architectural RES0/RES1 bits from
> the KVM masks.

No. Again.

	M.

-- 
Jazz isn't dead. It just smells funny.