Re: [PATCH v2 12/25] KVM: arm64: Enable GICv3 Group-1 sysreg trapping via command-line

Christoffer Dall
2017-06-06T12:06:56Z

On Thu, Jun 01, 2017 at 11:21:04AM +0100, Marc Zyngier wrote:
> Now that we're able to safely handle Group-1 sysreg access, let's
> give the user the opportunity to enable it by passing a specific
> command-line option (vgic_v3.group1_trap).
>
> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
> ---
> virt/kvm/arm/hyp/vgic-v3-sr.c | 6 +++++-
> virt/kvm/arm/vgic/vgic-v3.c | 11 +++++++++++
> 2 files changed, 16 insertions(+), 1 deletion(-)
>
> diff --git a/virt/kvm/arm/hyp/vgic-v3-sr.c b/virt/kvm/arm/hyp/vgic-v3-sr.c
> index 8973bad35748..42ac9ee7650a 100644
> --- a/virt/kvm/arm/hyp/vgic-v3-sr.c
> +++ b/virt/kvm/arm/hyp/vgic-v3-sr.c
> @@ -334,7 +334,11 @@ void __hyp_text __vgic_v3_restore_state(struct kvm_vcpu *vcpu)
> for (i = 0; i < used_lrs; i++)
> __gic_v3_set_lr(cpu_if->vgic_lr[i], i);
> } else {
> - /* Always write ICH_HCR_EL2 to enable trapping */
> + /*
> + * If we don't have any interrupt to inject, but that
> + * trapping is enabled, write the ICH_HCR_EL2 config
> + * anyway.
> + */

nit: Whitespace and grammar issues, and maybe this hunk was supposed to
be in the last patch?

> if (static_branch_unlikely(&vgic_v3_cpuif_trap))
> write_gicreg(cpu_if->vgic_hcr, ICH_HCR_EL2);
> }
> diff --git a/virt/kvm/arm/vgic/vgic-v3.c b/virt/kvm/arm/vgic/vgic-v3.c
> index fbd678bc046d..a16769276efd 100644
> --- a/virt/kvm/arm/vgic/vgic-v3.c
> +++ b/virt/kvm/arm/vgic/vgic-v3.c
> @@ -416,6 +416,12 @@ int vgic_v3_map_resources(struct kvm *kvm)
>
> DEFINE_STATIC_KEY_FALSE(vgic_v3_cpuif_trap);
>
> +static int __init early_group1_trap_cfg(char *buf)
> +{
> + return strtobool(buf, &group1_trap);
> +}
> +early_param("vgic_v3.group1_trap", early_group1_trap_cfg);
> +

this shouldn't be named something with KVM (we're not going to trap
anything on the host somehow are we?)?

> /**
> * vgic_v3_probe - probe for a GICv3 compatible interrupt controller in DT
> * @node: pointer to the DT node
> @@ -467,6 +473,11 @@ int vgic_v3_probe(const struct gic_kvm_info *info)
> if (kvm_vgic_global_state.vcpu_base == 0)
> kvm_info("disabling GICv2 emulation\n");
>
> + if (group1_trap) {
> + kvm_info("GICv3 sysreg trapping enabled (reduced performance)\n");
> + static_branch_enable(&vgic_v3_cpuif_trap);
> + }
> +
> kvm_vgic_global_state.vctrl_base = NULL;
> kvm_vgic_global_state.type = VGIC_V3;
> kvm_vgic_global_state.max_gic_vcpus = VGIC_V3_MAX_CPUS;
> --
> 2.11.0
>

Thanks,
-Christoffer