[RFC PATCH v2 02/28] KVM: arm64: Save ID registers' sanitized value per vCPU

[Reiji Watanabe]

Extend sys_regs[] of kvm_cpu_context for ID registers and save ID
registers' sanitized value in the array for the vCPU at the first
vCPU reset. Use the saved ones when ID registers are read by
userspace (via KVM_GET_ONE_REG) or the guest.

Signed-off-by: Reiji Watanabe <reijiw at google.com>
---
 arch/arm64/include/asm/kvm_host.h | 10 ++++++++++
 arch/arm64/kvm/sys_regs.c         | 24 ++++++++++++++++--------
 2 files changed, 26 insertions(+), 8 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 9b5e7a3b6011..0cd351099adf 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -145,6 +145,14 @@ struct kvm_vcpu_fault_info {
 	u64 disr_el1;		/* Deferred [SError] Status Register */
 };
 
+/*
+ * (Op0, Op1, CRn, CRm, Op2) of ID registers is (3, 0, 0, crm, op2),
+ * where 0<=crm<8, 0<=op2<8.
+ */
+#define KVM_ARM_ID_REG_MAX_NUM 64
+#define IDREG_IDX(id)		((sys_reg_CRm(id) << 3) | sys_reg_Op2(id))
+#define IDREG_SYS_IDX(id)	(ID_REG_BASE + IDREG_IDX(id))
+
 enum vcpu_sysreg {
 	__INVALID_SYSREG__,   /* 0 is reserved as an invalid value */
 	MPIDR_EL1,	/* MultiProcessor Affinity Register */
@@ -209,6 +217,8 @@ enum vcpu_sysreg {
 	CNTP_CVAL_EL0,
 	CNTP_CTL_EL0,
 
+	ID_REG_BASE,
+	ID_REG_END = ID_REG_BASE + KVM_ARM_ID_REG_MAX_NUM - 1,
 	/* Memory Tagging Extension registers */
 	RGSR_EL1,	/* Random Allocation Tag Seed Register */
 	GCR_EL1,	/* Tag Control Register */
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 1d46e185f31e..2443440720b4 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -273,7 +273,7 @@ static bool trap_loregion(struct kvm_vcpu *vcpu,
 			  struct sys_reg_params *p,
 			  const struct sys_reg_desc *r)
 {
-	u64 val = read_sanitised_ftr_reg(SYS_ID_AA64MMFR1_EL1);
+	u64 val = __vcpu_sys_reg(vcpu, IDREG_SYS_IDX(SYS_ID_AA64MMFR1_EL1));
 	u32 sr = reg_to_encoding(r);
 
 	if (!(val & (0xfUL << ID_AA64MMFR1_LOR_SHIFT))) {
@@ -1059,12 +1059,11 @@ static bool access_arch_timer(struct kvm_vcpu *vcpu,
 	return true;
 }
 
-/* Read a sanitised cpufeature ID register by sys_reg_desc */
 static u64 read_id_reg(const struct kvm_vcpu *vcpu,
 		struct sys_reg_desc const *r, bool raz)
 {
 	u32 id = reg_to_encoding(r);
-	u64 val = raz ? 0 : read_sanitised_ftr_reg(id);
+	u64 val = raz ? 0 : __vcpu_sys_reg(vcpu, IDREG_SYS_IDX(id));
 
 	switch (id) {
 	case SYS_ID_AA64PFR0_EL1:
@@ -1174,6 +1173,16 @@ static unsigned int sve_visibility(const struct kvm_vcpu *vcpu,
 	return REG_HIDDEN;
 }
 
+static void reset_id_reg(struct kvm_vcpu *vcpu, const struct sys_reg_desc *rd)
+{
+	u32 id = reg_to_encoding(rd);
+
+	if (vcpu_has_reset_once(vcpu))
+		return;
+
+	__vcpu_sys_reg(vcpu, IDREG_SYS_IDX(id)) = read_sanitised_ftr_reg(id);
+}
+
 static int set_id_aa64pfr0_el1(struct kvm_vcpu *vcpu,
 			       const struct sys_reg_desc *rd,
 			       const struct kvm_one_reg *reg, void __user *uaddr)
@@ -1219,9 +1228,7 @@ static int set_id_aa64pfr0_el1(struct kvm_vcpu *vcpu,
 /*
  * cpufeature ID register user accessors
  *
- * For now, these registers are immutable for userspace, so no values
- * are stored, and for set_id_reg() we don't allow the effective value
- * to be changed.
+ * We don't allow the effective value to be changed.
  */
 static int __get_id_reg(const struct kvm_vcpu *vcpu,
 			const struct sys_reg_desc *rd, void __user *uaddr,
@@ -1375,6 +1382,7 @@ static unsigned int mte_visibility(const struct kvm_vcpu *vcpu,
 #define ID_SANITISED(name) {			\
 	SYS_DESC(SYS_##name),			\
 	.access	= access_id_reg,		\
+	.reset	= reset_id_reg,			\
 	.get_user = get_id_reg,			\
 	.set_user = set_id_reg,			\
 	.visibility = id_visibility,		\
@@ -1830,8 +1838,8 @@ static bool trap_dbgdidr(struct kvm_vcpu *vcpu,
 	if (p->is_write) {
 		return ignore_write(vcpu, p);
 	} else {
-		u64 dfr = read_sanitised_ftr_reg(SYS_ID_AA64DFR0_EL1);
-		u64 pfr = read_sanitised_ftr_reg(SYS_ID_AA64PFR0_EL1);
+		u64 dfr = __vcpu_sys_reg(vcpu, IDREG_SYS_IDX(SYS_ID_AA64DFR0_EL1));
+		u64 pfr = __vcpu_sys_reg(vcpu, IDREG_SYS_IDX(SYS_ID_AA64PFR0_EL1));
 		u32 el3 = !!cpuid_feature_extract_unsigned_field(pfr, ID_AA64PFR0_EL3_SHIFT);
 
 		p->regval = ((((dfr >> ID_AA64DFR0_WRPS_SHIFT) & 0xf) << 28) |
-- 
2.33.1.1089.g2158813163f-goog