arm64: KVM: vgic-v2: Enable GICV access from HYP if access from guest is unsafe

So far, we've been disabling KVM on systems where the GICV region couldn't
be safely given to a guest. Now that we're able to handle this access
safely by emulating it in HYP, we can enable this feature when we detect
an unsafe configuration.

Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>

diff --git a/virt/kvm/arm/vgic/vgic-v2.c b/virt/kvm/arm/vgic/vgic-v2.c
index b8da901..0a063af 100644 (file)
--- a/virt/kvm/arm/vgic/vgic-v2.c
+++ b/virt/kvm/arm/vgic/vgic-v2.c
@@ -278,12 +278,14 @@ int vgic_v2_map_resources(struct kvm *kvm)
                goto out;
        }
 
-       ret = kvm_phys_addr_ioremap(kvm, dist->vgic_cpu_base,
-                                   kvm_vgic_global_state.vcpu_base,
-                                   KVM_VGIC_V2_CPU_SIZE, true);
-       if (ret) {
-               kvm_err("Unable to remap VGIC CPU to VCPU\n");
-               goto out;
+       if (!static_branch_unlikely(&vgic_v2_cpuif_trap)) {
+               ret = kvm_phys_addr_ioremap(kvm, dist->vgic_cpu_base,
+                                           kvm_vgic_global_state.vcpu_base,
+                                           KVM_VGIC_V2_CPU_SIZE, true);
+               if (ret) {
+                       kvm_err("Unable to remap VGIC CPU to VCPU\n");
+                       goto out;
+               }
        }
 
        dist->ready = true;
@@ -312,45 +314,51 @@ int vgic_v2_probe(const struct gic_kvm_info *info)
                return -ENXIO;
        }
 
-       if (!PAGE_ALIGNED(info->vcpu.start)) {
-               kvm_err("GICV physical address 0x%llx not page aligned\n",
-                       (unsigned long long)info->vcpu.start);
-               return -ENXIO;
-       }
+       if (!PAGE_ALIGNED(info->vcpu.start) ||
+           !PAGE_ALIGNED(resource_size(&info->vcpu))) {
+               kvm_info("GICV region size/alignment is unsafe, using trapping (reduced performance)\n");
+               kvm_vgic_global_state.vcpu_base_va = ioremap(info->vcpu.start,
+                                                            resource_size(&info->vcpu));
+               if (!kvm_vgic_global_state.vcpu_base_va) {
+                       kvm_err("Cannot ioremap GICV\n");
+                       return -ENOMEM;
+               }
 
-       if (!PAGE_ALIGNED(resource_size(&info->vcpu))) {
-               kvm_err("GICV size 0x%llx not a multiple of page size 0x%lx\n",
-                       (unsigned long long)resource_size(&info->vcpu),
-                       PAGE_SIZE);
-               return -ENXIO;
+               ret = create_hyp_io_mappings(kvm_vgic_global_state.vcpu_base_va,
+                                            kvm_vgic_global_state.vcpu_base_va + resource_size(&info->vcpu),
+                                            info->vcpu.start);
+               if (ret) {
+                       kvm_err("Cannot map GICV into hyp\n");
+                       goto out;
+               }
+
+               static_branch_enable(&vgic_v2_cpuif_trap);
        }
 
        kvm_vgic_global_state.vctrl_base = ioremap(info->vctrl.start,
                                                   resource_size(&info->vctrl));
        if (!kvm_vgic_global_state.vctrl_base) {
                kvm_err("Cannot ioremap GICH\n");
-               return -ENOMEM;
+               ret = -ENOMEM;
+               goto out;
        }
 
        vtr = readl_relaxed(kvm_vgic_global_state.vctrl_base + GICH_VTR);
        kvm_vgic_global_state.nr_lr = (vtr & 0x3f) + 1;
 
-       ret = kvm_register_vgic_device(KVM_DEV_TYPE_ARM_VGIC_V2);
-       if (ret) {
-               kvm_err("Cannot register GICv2 KVM device\n");
-               iounmap(kvm_vgic_global_state.vctrl_base);
-               return ret;
-       }
-
        ret = create_hyp_io_mappings(kvm_vgic_global_state.vctrl_base,
                                     kvm_vgic_global_state.vctrl_base +
                                         resource_size(&info->vctrl),
                                     info->vctrl.start);
        if (ret) {
                kvm_err("Cannot map VCTRL into hyp\n");
-               kvm_unregister_device_ops(KVM_DEV_TYPE_ARM_VGIC_V2);
-               iounmap(kvm_vgic_global_state.vctrl_base);
-               return ret;
+               goto out;
+       }
+
+       ret = kvm_register_vgic_device(KVM_DEV_TYPE_ARM_VGIC_V2);
+       if (ret) {
+               kvm_err("Cannot register GICv2 KVM device\n");
+               goto out;
        }
 
        kvm_vgic_global_state.can_emulate_gicv2 = true;
@@ -361,4 +369,11 @@ int vgic_v2_probe(const struct gic_kvm_info *info)
        kvm_info("vgic-v2@%llx\n", info->vctrl.start);
 
        return 0;
+out:
+       if (kvm_vgic_global_state.vctrl_base)
+               iounmap(kvm_vgic_global_state.vctrl_base);
+       if (kvm_vgic_global_state.vcpu_base_va)
+               iounmap(kvm_vgic_global_state.vcpu_base_va);
+
+       return ret;
 }