[PATCH 3/4] KVM: arm64: add emulation for CTR_EL0 register

[Sebastian Ott]

CTR_EL0 is currently handled as an invariant register, thus
guests will be presented with the host value of that register.
Add emulation for CTR_EL0 based on a per VM value.

When CTR_EL0 is changed the reset function for CLIDR_EL1 is
called to make sure we present the guest with consistent
register values.

Signed-off-by: Sebastian Ott <sebott@xxxxxxxxxx>
---
 arch/arm64/kvm/sys_regs.c | 72 ++++++++++++++++++++++++++++++++++-----
 1 file changed, 64 insertions(+), 8 deletions(-)

diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 4d29b1a0842d..b0ba292259f9 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -1874,6 +1874,55 @@ static bool access_ctr(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
 	return true;
 }
 
+static u64 reset_ctr(struct kvm_vcpu *vcpu, const struct sys_reg_desc *rd)
+{
+	vcpu->kvm->arch.ctr_el0 = 0;
+	return kvm_get_ctr_el0(vcpu->kvm);
+}
+
+static int get_ctr(struct kvm_vcpu *vcpu, const struct sys_reg_desc *rd,
+		   u64 *val)
+{
+	*val = kvm_get_ctr_el0(vcpu->kvm);
+	return 0;
+}
+
+static const struct sys_reg_desc *get_sys_reg_desc(u32 encoding);
+
+static int set_ctr(struct kvm_vcpu *vcpu, const struct sys_reg_desc *rd,
+		   u64 val)
+{
+	u64 host_val = read_sanitised_ftr_reg(SYS_CTR_EL0);
+	u64 old_val = kvm_get_ctr_el0(vcpu->kvm);
+	const struct sys_reg_desc *clidr_el1;
+	int ret;
+
+	if (val == old_val)
+		return 0;
+
+	if (kvm_vm_has_ran_once(vcpu->kvm))
+		return -EBUSY;
+
+	mutex_lock(&vcpu->kvm->arch.config_lock);
+	ret = arm64_check_features(vcpu, rd, val);
+	if (ret) {
+		mutex_unlock(&vcpu->kvm->arch.config_lock);
+		return ret;
+	}
+	if (val != host_val)
+		vcpu->kvm->arch.ctr_el0 = val;
+	else
+		vcpu->kvm->arch.ctr_el0 = 0;
+
+	mutex_unlock(&vcpu->kvm->arch.config_lock);
+
+	clidr_el1 = get_sys_reg_desc(SYS_CLIDR_EL1);
+	if (clidr_el1)
+		clidr_el1->reset(vcpu, clidr_el1);
+
+	return 0;
+}
+
 static bool access_clidr(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
 			 const struct sys_reg_desc *r)
 {
@@ -2460,7 +2509,11 @@ static const struct sys_reg_desc sys_reg_descs[] = {
 	{ SYS_DESC(SYS_CCSIDR2_EL1), undef_access },
 	{ SYS_DESC(SYS_SMIDR_EL1), undef_access },
 	{ SYS_DESC(SYS_CSSELR_EL1), access_csselr, reset_unknown, CSSELR_EL1 },
-	{ SYS_DESC(SYS_CTR_EL0), access_ctr },
+	{ SYS_DESC(SYS_CTR_EL0), access_ctr, .reset = reset_ctr,
+	  .get_user = get_ctr, .set_user = set_ctr, .val = (CTR_EL0_DIC_MASK |
+							    CTR_EL0_IDC_MASK |
+							    CTR_EL0_DminLine_MASK |
+							    CTR_EL0_IminLine_MASK)},
 	{ SYS_DESC(SYS_SVCR), undef_access },
 
 	{ PMU_SYS_REG(PMCR_EL0), .access = access_pmcr, .reset = reset_pmcr,
@@ -3623,6 +3676,13 @@ static bool index_to_params(u64 id, struct sys_reg_params *params)
 	}
 }
 
+static const struct sys_reg_desc *get_sys_reg_desc(u32 encoding)
+{
+	struct sys_reg_params params = encoding_to_params(encoding);
+
+	return find_reg(&params, sys_reg_descs, ARRAY_SIZE(sys_reg_descs));
+}
+
 const struct sys_reg_desc *get_reg_by_id(u64 id,
 					 const struct sys_reg_desc table[],
 					 unsigned int num)
@@ -3676,18 +3736,11 @@ FUNCTION_INVARIANT(midr_el1)
 FUNCTION_INVARIANT(revidr_el1)
 FUNCTION_INVARIANT(aidr_el1)
 
-static u64 get_ctr_el0(struct kvm_vcpu *v, const struct sys_reg_desc *r)
-{
-	((struct sys_reg_desc *)r)->val = read_sanitised_ftr_reg(SYS_CTR_EL0);
-	return ((struct sys_reg_desc *)r)->val;
-}
-
 /* ->val is filled in by kvm_sys_reg_table_init() */
 static struct sys_reg_desc invariant_sys_regs[] __ro_after_init = {
 	{ SYS_DESC(SYS_MIDR_EL1), NULL, get_midr_el1 },
 	{ SYS_DESC(SYS_REVIDR_EL1), NULL, get_revidr_el1 },
 	{ SYS_DESC(SYS_AIDR_EL1), NULL, get_aidr_el1 },
-	{ SYS_DESC(SYS_CTR_EL0), NULL, get_ctr_el0 },
 };
 
 static int get_invariant_sys_reg(u64 id, u64 __user *uaddr)
@@ -4049,6 +4102,9 @@ void kvm_init_sysreg(struct kvm_vcpu *vcpu)
 			vcpu->arch.hcrx_el2 |= (HCRX_EL2_MSCEn | HCRX_EL2_MCE2);
 	}
 
+	if (vcpu->kvm->arch.ctr_el0)
+		vcpu->arch.hcr_el2 |= HCR_TID2;
+
 	if (test_bit(KVM_ARCH_FLAG_FGU_INITIALIZED, &kvm->arch.flags))
 		goto out;
 
-- 
2.42.0