[PATCH v3 15/15] KVM: arm64: Restrict protected VM capabilities

[Fuad Tabba <tabba@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@google.com>
---
 arch/arm64/include/asm/kvm_fixed_config.h | 10 ++++
 arch/arm64/kvm/arm.c                      | 63 ++++++++++++++++++++++-
 arch/arm64/kvm/pkvm.c                     | 30 +++++++++++
 3 files changed, 102 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/kvm_fixed_config.h b/arch/arm64/include/asm/kvm_fixed_config.h
index b39a5de2c4b9..14310b035bf7 100644
--- a/arch/arm64/include/asm/kvm_fixed_config.h
+++ b/arch/arm64/include/asm/kvm_fixed_config.h
@@ -175,4 +175,14 @@
  */
 #define PVM_ID_AA64ISAR1_ALLOW (~0ULL)
 
+/*
+ * Returns the maximum number of breakpoints supported for protected VMs.
+ */
+int kvm_arm_pkvm_get_max_brps(void);
+
+/*
+ * Returns the maximum number of watchpoints supported for protected VMs.
+ */
+int kvm_arm_pkvm_get_max_wrps(void);
+
 #endif /* __ARM64_KVM_FIXED_CONFIG_H__ */
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 3f28549aff0d..bc41e3b71fab 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -34,6 +34,7 @@
 #include <asm/virt.h>
 #include <asm/kvm_arm.h>
 #include <asm/kvm_asm.h>
+#include <asm/kvm_fixed_config.h>
 #include <asm/kvm_mmu.h>
 #include <asm/kvm_emulate.h>
 #include <asm/sections.h>
@@ -188,9 +189,10 @@ void kvm_arch_destroy_vm(struct kvm *kvm)
 	atomic_set(&kvm->online_vcpus, 0);
 }
 
-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;
@@ -281,6 +283,65 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 	return r;
 }
 
+static int pkvm_check_extension(struct kvm *kvm, long ext, int kvm_cap)
+{
+	int r;
+
+	switch (ext) {
+	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:
+		r = kvm_cap;
+		break;
+	case KVM_CAP_ARM_EL1_32BIT:
+		r = kvm_cap &&
+		    (FIELD_GET(FEATURE(ID_AA64PFR0_EL1), PVM_ID_AA64PFR0_ALLOW) >=
+		     ID_AA64PFR0_ELx_32BIT_64BIT);
+		break;
+	case KVM_CAP_GUEST_DEBUG_HW_BPS:
+		r = min(kvm_cap, kvm_arm_pkvm_get_max_brps());
+		break;
+	case KVM_CAP_GUEST_DEBUG_HW_WPS:
+		r = min(kvm_cap, kvm_arm_pkvm_get_max_wrps());
+		break;
+	case KVM_CAP_ARM_PMU_V3:
+		r = kvm_cap &&
+		    FIELD_GET(FEATURE(ID_AA64DFR0_PMUVER), PVM_ID_AA64DFR0_ALLOW);
+		break;
+	case KVM_CAP_ARM_SVE:
+		r = kvm_cap &&
+		    FIELD_GET(FEATURE(ID_AA64PFR0_SVE), PVM_ID_AA64PFR0_ALLOW);
+		break;
+	case KVM_CAP_ARM_PTRAUTH_ADDRESS:
+		r = kvm_cap &&
+		    FIELD_GET(FEATURE(ID_AA64ISAR1_API), PVM_ID_AA64ISAR1_ALLOW) &&
+		    FIELD_GET(FEATURE(ID_AA64ISAR1_APA), PVM_ID_AA64ISAR1_ALLOW);
+		break;
+	case KVM_CAP_ARM_PTRAUTH_GENERIC:
+		r = kvm_cap &&
+		    FIELD_GET(FEATURE(ID_AA64ISAR1_GPI), PVM_ID_AA64ISAR1_ALLOW) &&
+		    FIELD_GET(FEATURE(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 (unlikely(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)
 {
diff --git a/arch/arm64/kvm/pkvm.c b/arch/arm64/kvm/pkvm.c
index b8430b3d97af..d41553594d08 100644
--- a/arch/arm64/kvm/pkvm.c
+++ b/arch/arm64/kvm/pkvm.c
@@ -181,3 +181,33 @@ void kvm_init_protected_traps(struct kvm_vcpu *vcpu)
 	pvm_init_traps_aa64mmfr0(vcpu);
 	pvm_init_traps_aa64mmfr1(vcpu);
 }
+
+int kvm_arm_pkvm_get_max_brps(void)
+{
+	int num = FIELD_GET(FEATURE(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.
+	 */
+	if (num)
+		return 1 + num;
+	else
+		return 0;
+}
+
+int kvm_arm_pkvm_get_max_wrps(void)
+{
+	int num = FIELD_GET(FEATURE(ID_AA64DFR0_WRPS), 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.
+	 */
+	if (num)
+		return 1 + num;
+	else
+		return 0;
+}
-- 
2.32.0.402.g57bb445576-goog