linux-kernel - Re: [PATCH v5 22/23] KVM: arm64: GICv4.1: Allow non-trapping WFI when using HW SGIs

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Date:   Fri, 20 Mar 2020 09:12:48 +0100
From:   Auger Eric <eric.auger@...hat.com>
To:     Marc Zyngier <maz@...nel.org>,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Jason Cooper <jason@...edaemon.net>,
        Robert Richter <rrichter@...vell.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Zenghui Yu <yuzenghui@...wei.com>,
        James Morse <james.morse@....com>,
        Julien Thierry <julien.thierry.kdev@...il.com>,
        Suzuki K Poulose <suzuki.poulose@....com>
Subject: Re: [PATCH v5 22/23] KVM: arm64: GICv4.1: Allow non-trapping WFI when
 using HW SGIs

Hi Marc,

On 3/4/20 9:33 PM, Marc Zyngier wrote:
> Just like for VLPIs, it is beneficial to avoid trapping on WFI when the
> vcpu is using the GICv4.1 SGIs.
> 
> Add such a check to vcpu_clear_wfx_traps().
> 
> Signed-off-by: Marc Zyngier <maz@...nel.org>
Reviewed-by: Eric Auger <eric.auger@...hat.com>

Thanks

Eric
> ---
>  arch/arm64/include/asm/kvm_emulate.h | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
> index f658dda12364..a30b4eec7cb4 100644
> --- a/arch/arm64/include/asm/kvm_emulate.h
> +++ b/arch/arm64/include/asm/kvm_emulate.h
> @@ -89,7 +89,8 @@ static inline unsigned long *vcpu_hcr(struct kvm_vcpu *vcpu)
>  static inline void vcpu_clear_wfx_traps(struct kvm_vcpu *vcpu)
>  {
>  	vcpu->arch.hcr_el2 &= ~HCR_TWE;
> -	if (atomic_read(&vcpu->arch.vgic_cpu.vgic_v3.its_vpe.vlpi_count))
> +	if (atomic_read(&vcpu->arch.vgic_cpu.vgic_v3.its_vpe.vlpi_count) ||
> +	    vcpu->kvm->arch.vgic.nassgireq)
>  		vcpu->arch.hcr_el2 &= ~HCR_TWI;
>  	else
>  		vcpu->arch.hcr_el2 |= HCR_TWI;
>