Re: [PATCH 05/28] KVM: arm64: Plumb HCRX_EL2.SRMASKEn in HCRX_EL2 sanitisation

[Marc Zyngier <maz@kernel.org>]

On Thu, 02 Jul 2026 17:28:15 +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] Missing RES0 constraints in system register feature map for `HCRX_EL2` allows nested guests to set reserved hardware bits.
> --
> 
> commit 5fb0fde52515a7e2e03636fdc18f15c38a091ddd
> Author: Marc Zyngier <maz@kernel.org>
> 
> KVM: arm64: Plumb HCRX_EL2.SRMASKEn in HCRX_EL2 sanitisation
> 
> This patch adds the HCRX_EL2.SRMASKEn bit to the HCRX_EL2 feature map to
> enable FEAT_SRMASK for a guest. It also updates the system register
> definitions to reflect the new bit field.
> 
> > diff --git a/arch/arm64/kvm/config.c b/arch/arm64/kvm/config.c
> > --- a/arch/arm64/kvm/config.c
> > +++ b/arch/arm64/kvm/config.c
> > @@ -904,6 +904,7 @@ static const DECLARE_FEAT_MAP_FGT(hdfgwtr2_desc, hdfgwtr2_masks,
> >  
> >  
> >  static const struct reg_bits_to_feat_map hcrx_feat_map[] = {
> > +	NEEDS_FEAT(HCRX_EL2_SRMASKEn, FEAT_SRMASK),
> 
> [Severity: High]
> This isn't a bug introduced by this patch, but a pre-existing issue in
> hcrx_feat_map: does the omission of FORCE_RES0(HCRX_EL2_RES0) and
> FORCE_RES1(HCRX_EL2_RES1) allow a nested guest to set architecturally reserved
> hardware bits?

No, because any bit that is not allocated will be treated as RES0, and
the kernel will warn about this. FORCE_RES0() is only an additional
way to detect these things.

Worth doing, but not a real issue.

	M.

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