[PATCH 5/5] arm64: KVM: vgic-v2: Enable GICV access from HYP if access from guest is unsafe

Marc Zyngier
2016-08-19T12:38:15Z

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.

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
---
virt/kvm/arm/vgic/vgic-v2.c | 69 +++++++++++++++++++++++++++------------------
1 file changed, 42 insertions(+), 27 deletions(-)

diff --git a/virt/kvm/arm/vgic/vgic-v2.c b/virt/kvm/arm/vgic/vgic-v2.c
index b8da901..d1dcfc76 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/alignement is unsafe, using trapping\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;
}
--
2.1.4