[PATCH] KVM: arm64: nv: Fix MI line level calculation in vgic_v3_nested_update_mi()
Marc Zyngier
maz at kernel.org
Wed Jun 25 09:45:06 PDT 2025
On Wed, 25 Jun 2025 09:47:09 +0100,
Wei-Lin Chang <r09922117 at csie.ntu.edu.tw> wrote:
>
> The state of the vcpu's MI line should be asserted when its
> ICH_HCR_EL2.En is set and ICH_MISR_EL2 is non-zero. Using bitwise AND
> (&=) directly for this calculation will not give us the correct result
> when the LSB of the vcpu's ICH_MISR_EL2 isn't set. Correct this by first
> adjusting the return value of vgic_v3_get_misr() into 1 if it is
> non-zero.
>
> Signed-off-by: Wei-Lin Chang <r09922117 at csie.ntu.edu.tw>
> ---
> arch/arm64/kvm/vgic/vgic-v3-nested.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/arm64/kvm/vgic/vgic-v3-nested.c b/arch/arm64/kvm/vgic/vgic-v3-nested.c
> index 4f6954c30674..ebffad632fd2 100644
> --- a/arch/arm64/kvm/vgic/vgic-v3-nested.c
> +++ b/arch/arm64/kvm/vgic/vgic-v3-nested.c
> @@ -400,7 +400,7 @@ void vgic_v3_nested_update_mi(struct kvm_vcpu *vcpu)
>
> level = __vcpu_sys_reg(vcpu, ICH_HCR_EL2) & ICH_HCR_EL2_En;
> if (level)
> - level &= vgic_v3_get_misr(vcpu);
> + level &= !!vgic_v3_get_misr(vcpu);
> kvm_vgic_inject_irq(vcpu->kvm, vcpu,
> vcpu->kvm->arch.vgic.mi_intid, level, vcpu);
> }
Very well spotted, once more. Where were you when I posted all these
patches? ;-)
We could make it even clearer with this:
diff --git a/arch/arm64/kvm/vgic/vgic-v3-nested.c b/arch/arm64/kvm/vgic/vgic-v3-nested.c
index a50fb7e6841f7..679aafe77de2e 100644
--- a/arch/arm64/kvm/vgic/vgic-v3-nested.c
+++ b/arch/arm64/kvm/vgic/vgic-v3-nested.c
@@ -401,9 +401,7 @@ void vgic_v3_nested_update_mi(struct kvm_vcpu *vcpu)
{
bool level;
- level = __vcpu_sys_reg(vcpu, ICH_HCR_EL2) & ICH_HCR_EL2_En;
- if (level)
- level &= vgic_v3_get_misr(vcpu);
+ level = (__vcpu_sys_reg(vcpu, ICH_HCR_EL2) & ICH_HCR_EL2_En) && vgic_v3_get_misr(vcpu);
kvm_vgic_inject_irq(vcpu->kvm, vcpu,
vcpu->kvm->arch.vgic.mi_intid, level, vcpu);
}
If you're OK with it, I'll use this, keeping your authorship of
course.
Thanks,
M.
--
Without deviation from the norm, progress is not possible.
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