[PATCH v3 5/6] KVM: arm64: Make ID_AA64PFR1_EL1.RAS_frac writable

[Marc Zyngier <maz@kernel.org>]

Allow userspace to write to RAS_frac, under the condition that
the host supports RASv1p1 with RAS_frac==1. Other configurations
will result in RAS_frac being exposed as 0, and therefore implicitly
not writable.

To avoid the clutter, the ID_AA64PFR1_EL1 sanitisation is moved to
its own function.

Signed-off-by: Marc Zyngier <maz@kernel.org>
---
 arch/arm64/kvm/nested.c   |  3 ++-
 arch/arm64/kvm/sys_regs.c | 41 ++++++++++++++++++++++++++-------------
 2 files changed, 29 insertions(+), 15 deletions(-)

diff --git a/arch/arm64/kvm/nested.c b/arch/arm64/kvm/nested.c
index 153b3e11b115d..1b0aedacc3f59 100644
--- a/arch/arm64/kvm/nested.c
+++ b/arch/arm64/kvm/nested.c
@@ -1458,9 +1458,10 @@ u64 limit_nv_id_reg(struct kvm *kvm, u32 reg, u64 val)
 		break;
 
 	case SYS_ID_AA64PFR1_EL1:
-		/* Only support BTI, SSBS, CSV2_frac */
+		/* Only support BTI, SSBS, RAS_frac, CSV2_frac */
 		val &= (ID_AA64PFR1_EL1_BT	|
 			ID_AA64PFR1_EL1_SSBS	|
+			ID_AA64PFR1_EL1_RAS_frac|
 			ID_AA64PFR1_EL1_CSV2_frac);
 		break;
 
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 3306fef432cbb..e149786f8bde0 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -1584,6 +1584,7 @@ static u8 pmuver_to_perfmon(u8 pmuver)
 }
 
 static u64 sanitise_id_aa64pfr0_el1(const struct kvm_vcpu *vcpu, u64 val);
+static u64 sanitise_id_aa64pfr1_el1(const struct kvm_vcpu *vcpu, u64 val);
 static u64 sanitise_id_aa64dfr0_el1(const struct kvm_vcpu *vcpu, u64 val);
 
 /* Read a sanitised cpufeature ID register by sys_reg_desc */
@@ -1606,19 +1607,7 @@ static u64 __kvm_read_sanitised_id_reg(const struct kvm_vcpu *vcpu,
 		val = sanitise_id_aa64pfr0_el1(vcpu, val);
 		break;
 	case SYS_ID_AA64PFR1_EL1:
-		if (!kvm_has_mte(vcpu->kvm)) {
-			val &= ~ARM64_FEATURE_MASK(ID_AA64PFR1_EL1_MTE);
-			val &= ~ARM64_FEATURE_MASK(ID_AA64PFR1_EL1_MTE_frac);
-		}
-
-		val &= ~ARM64_FEATURE_MASK(ID_AA64PFR1_EL1_SME);
-		val &= ~ARM64_FEATURE_MASK(ID_AA64PFR1_EL1_RNDR_trap);
-		val &= ~ARM64_FEATURE_MASK(ID_AA64PFR1_EL1_NMI);
-		val &= ~ARM64_FEATURE_MASK(ID_AA64PFR1_EL1_GCS);
-		val &= ~ARM64_FEATURE_MASK(ID_AA64PFR1_EL1_THE);
-		val &= ~ARM64_FEATURE_MASK(ID_AA64PFR1_EL1_MTEX);
-		val &= ~ARM64_FEATURE_MASK(ID_AA64PFR1_EL1_PFAR);
-		val &= ~ARM64_FEATURE_MASK(ID_AA64PFR1_EL1_MPAM_frac);
+		val = sanitise_id_aa64pfr1_el1(vcpu, val);
 		break;
 	case SYS_ID_AA64PFR2_EL1:
 		val &= ID_AA64PFR2_EL1_FPMR |
@@ -1836,6 +1825,31 @@ static u64 sanitise_id_aa64pfr0_el1(const struct kvm_vcpu *vcpu, u64 val)
 	return val;
 }
 
+static u64 sanitise_id_aa64pfr1_el1(const struct kvm_vcpu *vcpu, u64 val)
+{
+	u64 pfr0 = read_sanitised_ftr_reg(SYS_ID_AA64PFR0_EL1);
+
+	if (!kvm_has_mte(vcpu->kvm)) {
+		val &= ~ARM64_FEATURE_MASK(ID_AA64PFR1_EL1_MTE);
+		val &= ~ARM64_FEATURE_MASK(ID_AA64PFR1_EL1_MTE_frac);
+	}
+
+	if (!(cpus_have_final_cap(ARM64_HAS_RASV1P1_EXTN) &&
+	      SYS_FIELD_GET(ID_AA64PFR0_EL1, RAS, pfr0) == ID_AA64PFR0_EL1_RAS_IMP))
+		val &= ~ARM64_FEATURE_MASK(ID_AA64PFR1_EL1_RAS_frac);
+
+	val &= ~ARM64_FEATURE_MASK(ID_AA64PFR1_EL1_SME);
+	val &= ~ARM64_FEATURE_MASK(ID_AA64PFR1_EL1_RNDR_trap);
+	val &= ~ARM64_FEATURE_MASK(ID_AA64PFR1_EL1_NMI);
+	val &= ~ARM64_FEATURE_MASK(ID_AA64PFR1_EL1_GCS);
+	val &= ~ARM64_FEATURE_MASK(ID_AA64PFR1_EL1_THE);
+	val &= ~ARM64_FEATURE_MASK(ID_AA64PFR1_EL1_MTEX);
+	val &= ~ARM64_FEATURE_MASK(ID_AA64PFR1_EL1_PFAR);
+	val &= ~ARM64_FEATURE_MASK(ID_AA64PFR1_EL1_MPAM_frac);
+
+	return val;
+}
+
 static u64 sanitise_id_aa64dfr0_el1(const struct kvm_vcpu *vcpu, u64 val)
 {
 	val = ID_REG_LIMIT_FIELD_ENUM(val, ID_AA64DFR0_EL1, DebugVer, V8P8);
@@ -2954,7 +2968,6 @@ static const struct sys_reg_desc sys_reg_descs[] = {
 				       ID_AA64PFR1_EL1_SME |
 				       ID_AA64PFR1_EL1_RES0 |
 				       ID_AA64PFR1_EL1_MPAM_frac |
-				       ID_AA64PFR1_EL1_RAS_frac |
 				       ID_AA64PFR1_EL1_MTE)),
 	ID_WRITABLE(ID_AA64PFR2_EL1,
 		    ID_AA64PFR2_EL1_FPMR |
-- 
2.39.2