On Wed, Feb 17, 2016 at 04:40:46PM +0000, Marc Zyngier wrote:
> Next on our list of useless accesses is the maintenance interrupt
> status registers (ICH_MISR_EL2, ICH_EISR_EL2).
>
> It is pointless to save them if we haven't asked for a maintenance
> interrupt the first place, which can only happen for two reasons:
> - Underflow: ICH_HCR_UIE will be set,
> - EOI: ICH_LR_EOI will be set.
>
> These conditions can be checked on the in-memory copies of the regs.
> Should any of these two condition be valid, we must read GICH_MISR.
> We can then check for ICH_MISR_EOI, and only when set read
> ICH_EISR_EL2.
>
> This means that in most case, we don't have to save them at all.
>
> Signed-off-by: Marc Zyngier <marc.zyngier@xxxxxxx>
> ---
> arch/arm64/kvm/hyp/vgic-v3-sr.c | 34 ++++++++++++++++++++++++++++++++--
> 1 file changed, 32 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm64/kvm/hyp/vgic-v3-sr.c b/arch/arm64/kvm/hyp/vgic-v3-sr.c
> index b62c923..3463c0a 100644
> --- a/arch/arm64/kvm/hyp/vgic-v3-sr.c
> +++ b/arch/arm64/kvm/hyp/vgic-v3-sr.c
> @@ -133,6 +133,36 @@ static void __hyp_text __gic_v3_set_lr(u64 val, int lr)
> }
> }
>
> +static void __hyp_text save_maint_int_state(struct kvm_vcpu *vcpu, int nr_lr)
> +{
> + struct vgic_v3_cpu_if *cpu_if = &vcpu->arch.vgic_cpu.vgic_v3;
> + int i;
> + bool expect_mi;
> +
> + expect_mi = !!(cpu_if->vgic_hcr & ICH_HCR_UIE);
> +
> + for (i = 0; i < nr_lr; i++) {
> + if (!(vcpu->arch.vgic_cpu.live_lrs & (1UL << i)))
> + continue;
> +
> + expect_mi |= (!(cpu_if->vgic_lr[i] & ICH_LR_HW) &&
> + (cpu_if->vgic_lr[i] & ICH_LR_EOI));
> + }
> +
> + if (expect_mi) {
> + cpu_if->vgic_misr = read_gicreg(ICH_MISR_EL2);
> +
> + if (cpu_if->vgic_misr & ICH_MISR_EOI) {
> + cpu_if->vgic_eisr = read_gicreg(ICH_EISR_EL2);
> + } else {
> + cpu_if->vgic_eisr = 0;
> + }
nit: you can drop the curly braces here
> + } else {
> + cpu_if->vgic_misr = 0;
> + cpu_if->vgic_eisr = 0;
> + }
> +}
> +
> void __hyp_text __vgic_v3_save_state(struct kvm_vcpu *vcpu)
> {
> struct vgic_v3_cpu_if *cpu_if = &vcpu->arch.vgic_cpu.vgic_v3;
> @@ -150,8 +180,6 @@ void __hyp_text __vgic_v3_save_state(struct kvm_vcpu *vcpu)
> int i;
> u32 max_lr_idx, nr_pri_bits;
>
> - cpu_if->vgic_misr = read_gicreg(ICH_MISR_EL2);
> - cpu_if->vgic_eisr = read_gicreg(ICH_EISR_EL2);
> cpu_if->vgic_elrsr = read_gicreg(ICH_ELSR_EL2);
>
> write_gicreg(0, ICH_HCR_EL2);
> @@ -159,6 +187,8 @@ void __hyp_text __vgic_v3_save_state(struct kvm_vcpu *vcpu)
> max_lr_idx = vtr_to_max_lr_idx(val);
> nr_pri_bits = vtr_to_nr_pri_bits(val);
>
> + save_maint_int_state(vcpu, max_lr_idx + 1);
> +
> for (i = 0; i <= max_lr_idx; i++) {
> if (vcpu->arch.vgic_cpu.live_lrs & (1UL << i))
> cpu_if->vgic_lr[i] = __gic_v3_get_lr(i);
> --
> 2.1.4
>
Reviewed-by: Christoffer Dall <christoffer.dall@xxxxxxxxxx>
--
To unsubscribe from this list: send the line "unsubscribe kvm" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
