[PATCH 58/89] KVM: arm64: Restrict protected VM capabilities

[Will Deacon]

From: Fuad Tabba <tabba at google.com>

Restrict protected VM capabilities based on the
fixed-configuration for protected VMs.

No functional change intended in current KVM-supported modes
(nVHE, VHE).

Signed-off-by: Fuad Tabba <tabba at google.com>
---
 arch/arm64/include/asm/kvm_pkvm.h | 27 ++++++++++++
 arch/arm64/kvm/arm.c              | 69 ++++++++++++++++++++++++++++++-
 2 files changed, 95 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/kvm_pkvm.h b/arch/arm64/include/asm/kvm_pkvm.h
index b92440cfb5b4..6f13f62558dd 100644
--- a/arch/arm64/include/asm/kvm_pkvm.h
+++ b/arch/arm64/include/asm/kvm_pkvm.h
@@ -208,6 +208,33 @@ void kvm_shadow_destroy(struct kvm *kvm);
 	ARM64_FEATURE_MASK(ID_AA64ISAR2_APA3) \
 	)
 
+/*
+ * Returns the maximum number of breakpoints supported for protected VMs.
+ */
+static inline int pkvm_get_max_brps(void)
+{
+	int num = FIELD_GET(ARM64_FEATURE_MASK(ID_AA64DFR0_BRPS),
+			    PVM_ID_AA64DFR0_ALLOW);
+
+	/*
+	 * If breakpoints are supported, the maximum number is 1 + the field.
+	 * Otherwise, return 0, which is not compliant with the architecture,
+	 * but is reserved and is used here to indicate no debug support.
+	 */
+	return num ? num + 1 : 0;
+}
+
+/*
+ * Returns the maximum number of watchpoints supported for protected VMs.
+ */
+static inline int pkvm_get_max_wrps(void)
+{
+	int num = FIELD_GET(ARM64_FEATURE_MASK(ID_AA64DFR0_WRPS),
+			    PVM_ID_AA64DFR0_ALLOW);
+
+	return num ? num + 1 : 0;
+}
+
 extern struct memblock_region kvm_nvhe_sym(hyp_memory)[];
 extern unsigned int kvm_nvhe_sym(hyp_memblock_nr);
 
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 7c57c14e173a..10e036bf06e3 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -194,9 +194,10 @@ void kvm_arch_destroy_vm(struct kvm *kvm)
 	kvm_unshare_hyp(kvm, kvm + 1);
 }
 
-int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
+static int kvm_check_extension(struct kvm *kvm, long ext)
 {
 	int r;
+
 	switch (ext) {
 	case KVM_CAP_IRQCHIP:
 		r = vgic_present;
@@ -294,6 +295,72 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 	return r;
 }
 
+/*
+ * Checks whether the extension specified in ext is supported in protected
+ * mode for the specified vm.
+ * The capabilities supported by kvm in general are passed in kvm_cap.
+ */
+static int pkvm_check_extension(struct kvm *kvm, long ext, int kvm_cap)
+{
+	int r;
+
+	switch (ext) {
+	case KVM_CAP_IRQCHIP:
+	case KVM_CAP_ARM_PSCI:
+	case KVM_CAP_ARM_PSCI_0_2:
+	case KVM_CAP_NR_VCPUS:
+	case KVM_CAP_MAX_VCPUS:
+	case KVM_CAP_MAX_VCPU_ID:
+	case KVM_CAP_MSI_DEVID:
+	case KVM_CAP_ARM_VM_IPA_SIZE:
+		r = kvm_cap;
+		break;
+	case KVM_CAP_GUEST_DEBUG_HW_BPS:
+		r = min(kvm_cap, pkvm_get_max_brps());
+		break;
+	case KVM_CAP_GUEST_DEBUG_HW_WPS:
+		r = min(kvm_cap, pkvm_get_max_wrps());
+		break;
+	case KVM_CAP_ARM_PMU_V3:
+		r = kvm_cap && FIELD_GET(ARM64_FEATURE_MASK(ID_AA64DFR0_PMUVER),
+					 PVM_ID_AA64DFR0_ALLOW);
+		break;
+	case KVM_CAP_ARM_SVE:
+		r = kvm_cap && FIELD_GET(ARM64_FEATURE_MASK(ID_AA64PFR0_SVE),
+					 PVM_ID_AA64PFR0_RESTRICT_UNSIGNED);
+		break;
+	case KVM_CAP_ARM_PTRAUTH_ADDRESS:
+		r = kvm_cap &&
+		    FIELD_GET(ARM64_FEATURE_MASK(ID_AA64ISAR1_API),
+			      PVM_ID_AA64ISAR1_ALLOW) &&
+		    FIELD_GET(ARM64_FEATURE_MASK(ID_AA64ISAR1_APA),
+			      PVM_ID_AA64ISAR1_ALLOW);
+		break;
+	case KVM_CAP_ARM_PTRAUTH_GENERIC:
+		r = kvm_cap &&
+		    FIELD_GET(ARM64_FEATURE_MASK(ID_AA64ISAR1_GPI),
+			      PVM_ID_AA64ISAR1_ALLOW) &&
+		    FIELD_GET(ARM64_FEATURE_MASK(ID_AA64ISAR1_GPA),
+			      PVM_ID_AA64ISAR1_ALLOW);
+		break;
+	default:
+		r = 0;
+		break;
+	}
+
+	return r;
+}
+
+int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
+{
+	int r = kvm_check_extension(kvm, ext);
+
+	if (kvm && kvm_vm_is_protected(kvm))
+		r = pkvm_check_extension(kvm, ext, r);
+
+	return r;
+}
+
 long kvm_arch_dev_ioctl(struct file *filp,
 			unsigned int ioctl, unsigned long arg)
 {
-- 
2.36.1.124.g0e6072fb45-goog