KVM: arm64: Enable GICv3 Group-1 sysreg trapping via command-line

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).

Tested-by: Alexander Graf <agraf@suse.de>
Acked-by: David Daney <david.daney@cavium.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Acked-by: Christoffer Dall <cdall@linaro.org>
Signed-off-by: Christoffer Dall <cdall@linaro.org>

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 15f79c2..42fe395 100644 (file)
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1829,6 +1829,10 @@
                        for all guests.
                        Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
 
+       kvm-arm.vgic_v3_group1_trap=
+                       [KVM,ARM] Trap guest accesses to GICv3 group-1
+                       system registers
+
        kvm-intel.ept=  [KVM,Intel] Disable extended page tables
                        (virtualized MMU) support on capable Intel chips.
                        Default is 1 (enabled)

diff --git a/virt/kvm/arm/vgic/vgic-v3.c b/virt/kvm/arm/vgic/vgic-v3.c
index 722bdeb..4b2b62b 100644 (file)
--- a/virt/kvm/arm/vgic/vgic-v3.c
+++ b/virt/kvm/arm/vgic/vgic-v3.c
@@ -435,6 +435,12 @@ out:
 
 DEFINE_STATIC_KEY_FALSE(vgic_v3_cpuif_trap);
 
+static int __init early_group1_trap_cfg(char *buf)
+{
+       return strtobool(buf, &group1_trap);
+}
+early_param("kvm-arm.vgic_v3_group1_trap", early_group1_trap_cfg);
+
 /**
  * vgic_v3_probe - probe for a GICv3 compatible interrupt controller in DT
  * @node:      pointer to the DT node
@@ -486,6 +492,11 @@ 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;