Re: [PATCH 1/2] KVM: arm64: Just advertise SEIS as 0 when emulating ICC_CTLR_EL1

[Marc Zyngier <maz@kernel.org>]

On Tue, 22 Oct 2024 15:40:15 +0100,
Will Deacon <will@kernel.org> wrote:
> 
> ICC_CTLR_EL1 accesses from a guest are trapped and emulated on systems
> with broken SEIS support and without FEAT_GICv3_TDIR. On such systems,
> we mask SEIS support in 'kvm_vgic_global_state.ich_vtr_el2' and so the
> value of ICC_CTLR_EL1.SEIS visible to the guest is always zero.
>
> Simplify the ICC_CTLR_EL1 read emulation to return 0 for the SEIS field,
> rather than reading an always-zero value from the global state.
> 
> Cc: Marc Zyngier <maz@kernel.org>
> Cc: Oliver Upton <oliver.upton@linux.dev>
> Signed-off-by: Will Deacon <will@kernel.org>
> ---
>  arch/arm64/kvm/hyp/vgic-v3-sr.c | 3 ---
>  1 file changed, 3 deletions(-)
> 
> diff --git a/arch/arm64/kvm/hyp/vgic-v3-sr.c b/arch/arm64/kvm/hyp/vgic-v3-sr.c
> index 18d4677002b1..3f9741e51d41 100644
> --- a/arch/arm64/kvm/hyp/vgic-v3-sr.c
> +++ b/arch/arm64/kvm/hyp/vgic-v3-sr.c
> @@ -1012,9 +1012,6 @@ static void __vgic_v3_read_ctlr(struct kvm_vcpu *vcpu, u32 vmcr, int rt)
>  	val = ((vtr >> 29) & 7) << ICC_CTLR_EL1_PRI_BITS_SHIFT;
>  	/* IDbits */
>  	val |= ((vtr >> 23) & 7) << ICC_CTLR_EL1_ID_BITS_SHIFT;
> -	/* SEIS */
> -	if (kvm_vgic_global_state.ich_vtr_el2 & ICH_VTR_SEIS_MASK)
> -		val |= BIT(ICC_CTLR_EL1_SEIS_SHIFT);
>  	/* A3V */
>  	val |= ((vtr >> 21) & 1) << ICC_CTLR_EL1_A3V_SHIFT;
>  	/* EOImode */

Reviewed-by: Marc Zyngier <maz@kernel.org>

	M.

-- 
Without deviation from the norm, progress is not possible.