[PATCH 1/4] KVM: arm64: add emulation for CTR_EL0 register

From: Sebastian Ott <sebott@redhat.com>
To: linux-arm-kernel@lists.infradead.org
Cc: Marc Zyngier <maz@kernel.org>, Oliver Upton <oliver.upton@linux.dev>
Subject: [PATCH 1/4] KVM: arm64: add emulation for CTR_EL0 register
Date: Mon, 18 Mar 2024 12:16:33 +0100	[thread overview]
Message-ID: <20240318111636.10613-2-sebott@redhat.com> (raw)
In-Reply-To: <20240318111636.10613-1-sebott@redhat.com>

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 and maintain a per vcpu value. The
only thing that is allowed to be changed compared to the host
value is to switch off the DIC bit which describes Icache
invalidation requirements.

Signed-off-by: Sebastian Ott <sebott@redhat.com>
---
 arch/arm64/kvm/sys_regs.c | 44 +++++++++++++++++++++++++++++++--------
 1 file changed, 35 insertions(+), 9 deletions(-)

diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 30253bd19917..b2019faa9d73 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -1871,10 +1871,42 @@ static bool access_ctr(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
 	if (p->is_write)
 		return write_to_read_only(vcpu, p, r);
 
-	p->regval = read_sanitised_ftr_reg(SYS_CTR_EL0);
+	p->regval = __vcpu_sys_reg(vcpu, r->reg);
 	return true;
 }
 
+static u64 reset_ctr(struct kvm_vcpu *vcpu, const struct sys_reg_desc *rd)
+{
+	u64 val = read_sanitised_ftr_reg(SYS_CTR_EL0);
+
+	__vcpu_sys_reg(vcpu, rd->reg) = val;
+	return __vcpu_sys_reg(vcpu, rd->reg);
+}
+
+static int get_ctr(struct kvm_vcpu *vcpu, const struct sys_reg_desc *rd,
+		   u64 *val)
+{
+	*val = __vcpu_sys_reg(vcpu, rd->reg);
+	return 0;
+}
+
+static int set_ctr(struct kvm_vcpu *vcpu, const struct sys_reg_desc *rd,
+		   u64 val)
+{
+	u64 ctr_el0 = read_sanitised_ftr_reg(SYS_CTR_EL0);
+
+	if (kvm_vm_has_ran_once(vcpu->kvm) &&
+	    val != __vcpu_sys_reg(vcpu, rd->reg))
+		return -EBUSY;
+
+	if (((ctr_el0 & ~CTR_EL0_DIC_MASK) != (val & ~CTR_EL0_DIC_MASK)) ||
+	    ((ctr_el0 & CTR_EL0_DIC_MASK) < (val & CTR_EL0_DIC_MASK)))
+		return -EINVAL;
+
+	__vcpu_sys_reg(vcpu, rd->reg) = val;
+	return 0;
+}
+
 static bool access_clidr(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
 			 const struct sys_reg_desc *r)
 {
@@ -2461,7 +2493,8 @@ 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},
 	{ SYS_DESC(SYS_SVCR), undef_access },
 
 	{ PMU_SYS_REG(PMCR_EL0), .access = access_pmcr, .reset = reset_pmcr,
@@ -3578,18 +3611,11 @@ 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)
-- 
2.42.0


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