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>

1 files changed, 42 insertions, 27 deletions

diff --git a/virt/kvm/arm/vgic/vgic-v2.c b/virt/kvm/arm/vgic/vgic-v2.c
index b8da9011889d..0a063af40565 100644
--- 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;
 }