[RFC PATCH v4 05/26] KVM: arm64: Make ID_AA64PFR1_EL1 writable

[Reiji Watanabe]

This patch adds id_reg_info for ID_AA64PFR1_EL1 to make it writable
by userspace.

Return an error if userspace tries to set MTE field of the register
to a value that conflicts with KVM_CAP_ARM_MTE configuration for
the guest.
Skip fractional feature fields validation at present and they will
be handled by the following patches.

Signed-off-by: Reiji Watanabe <reijiw at google.com>
---
 arch/arm64/include/asm/sysreg.h |  1 +
 arch/arm64/kvm/sys_regs.c       | 42 +++++++++++++++++++++++++++++----
 2 files changed, 39 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
index e26027817171..f55513002281 100644
--- a/arch/arm64/include/asm/sysreg.h
+++ b/arch/arm64/include/asm/sysreg.h
@@ -801,6 +801,7 @@
 #define ID_AA64PFR0_GIC3		0x1
 
 /* id_aa64pfr1 */
+#define ID_AA64PFR1_CSV2FRAC_SHIFT	32
 #define ID_AA64PFR1_MPAMFRAC_SHIFT	16
 #define ID_AA64PFR1_RASFRAC_SHIFT	12
 #define ID_AA64PFR1_MTE_SHIFT		8
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 1eb5c5fb614f..ae9ca341a2e4 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -359,6 +359,21 @@ static int validate_id_aa64pfr0_el1(struct kvm_vcpu *vcpu,
 	return 0;
 }
 
+static int validate_id_aa64pfr1_el1(struct kvm_vcpu *vcpu,
+				    const struct id_reg_info *id_reg, u64 val)
+{
+	bool kvm_mte = kvm_has_mte(vcpu->kvm);
+	unsigned int mte;
+
+	mte = cpuid_feature_extract_unsigned_field(val, ID_AA64PFR1_MTE_SHIFT);
+
+	/* Check if there is a conflict with a request via KVM_ARM_VCPU_INIT. */
+	if (kvm_mte ^ (mte > 0))
+		return -EPERM;
+
+	return 0;
+}
+
 static void init_id_aa64pfr0_el1_info(struct id_reg_info *id_reg)
 {
 	u64 limit = id_reg->vcpu_limit_val;
@@ -390,12 +405,24 @@ static void init_id_aa64pfr0_el1_info(struct id_reg_info *id_reg)
 	id_reg->vcpu_limit_val = limit;
 }
 
+static void init_id_aa64pfr1_el1_info(struct id_reg_info *id_reg)
+{
+	if (!system_supports_mte())
+		id_reg->vcpu_limit_val &= ~ARM64_FEATURE_MASK(ID_AA64PFR1_MTE);
+}
+
 static u64 vcpu_mask_id_aa64pfr0_el1(const struct kvm_vcpu *vcpu,
 					 const struct id_reg_info *idr)
 {
 	return vcpu_has_sve(vcpu) ? 0 : ARM64_FEATURE_MASK(ID_AA64PFR0_SVE);
 }
 
+static u64 vcpu_mask_id_aa64pfr1_el1(const struct kvm_vcpu *vcpu,
+					 const struct id_reg_info *idr)
+{
+	return kvm_has_mte(vcpu->kvm) ? 0 : (ARM64_FEATURE_MASK(ID_AA64PFR1_MTE));
+}
+
 static struct id_reg_info id_aa64pfr0_el1_info = {
 	.sys_reg = SYS_ID_AA64PFR0_EL1,
 	.ignore_mask = ARM64_FEATURE_MASK(ID_AA64PFR0_GIC),
@@ -404,6 +431,16 @@ static struct id_reg_info id_aa64pfr0_el1_info = {
 	.vcpu_mask = vcpu_mask_id_aa64pfr0_el1,
 };
 
+static struct id_reg_info id_aa64pfr1_el1_info = {
+	.sys_reg = SYS_ID_AA64PFR1_EL1,
+	.ignore_mask = ARM64_FEATURE_MASK(ID_AA64PFR1_RASFRAC) |
+		       ARM64_FEATURE_MASK(ID_AA64PFR1_MPAMFRAC) |
+		       ARM64_FEATURE_MASK(ID_AA64PFR1_CSV2FRAC),
+	.init = init_id_aa64pfr1_el1_info,
+	.validate = validate_id_aa64pfr1_el1,
+	.vcpu_mask = vcpu_mask_id_aa64pfr1_el1,
+};
+
 /*
  * An ID register that needs special handling to control the value for the
  * guest must have its own id_reg_info in id_reg_info_table.
@@ -414,6 +451,7 @@ static struct id_reg_info id_aa64pfr0_el1_info = {
 #define	GET_ID_REG_INFO(id)	(id_reg_info_table[IDREG_IDX(id)])
 static struct id_reg_info *id_reg_info_table[KVM_ARM_ID_REG_MAX_NUM] = {
 	[IDREG_IDX(SYS_ID_AA64PFR0_EL1)] = &id_aa64pfr0_el1_info,
+	[IDREG_IDX(SYS_ID_AA64PFR1_EL1)] = &id_aa64pfr1_el1_info,
 };
 
 static int validate_id_reg(struct kvm_vcpu *vcpu, u32 id, u64 val)
@@ -1331,10 +1369,6 @@ static u64 __read_id_reg(const struct kvm_vcpu *vcpu, u32 id)
 		val &= ~(id_reg->vcpu_mask(vcpu, id_reg));
 
 	switch (id) {
-	case SYS_ID_AA64PFR1_EL1:
-		if (!kvm_has_mte(vcpu->kvm))
-			val &= ~ARM64_FEATURE_MASK(ID_AA64PFR1_MTE);
-		break;
 	case SYS_ID_AA64ISAR1_EL1:
 		if (!vcpu_has_ptrauth(vcpu))
 			val &= ~(ARM64_FEATURE_MASK(ID_AA64ISAR1_APA) |
-- 
2.34.1.448.ga2b2bfdf31-goog