[PATCH v7 02/38] KVM: arm64: Save ID registers' sanitized value per guest

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Introduce id_regs[] in kvm_arch as a storage of guest's ID registers,
and save ID registers' sanitized value in the array at KVM_CREATE_VM.
Use the saved ones when ID registers are read by the guest or
userspace (via KVM_GET_ONE_REG).

Signed-off-by: Reiji Watanabe <reijiw@xxxxxxxxxx>
---
 arch/arm64/include/asm/kvm_host.h | 11 +++++
 arch/arm64/kvm/arm.c              |  1 +
 arch/arm64/kvm/sys_regs.c         | 81 +++++++++++++++++++++++++------
 3 files changed, 78 insertions(+), 15 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 94a27a7520f4..fc836df84748 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -150,6 +150,15 @@ struct kvm_arch {
 
 	u8 pfr0_csv2;
 	u8 pfr0_csv3;
+
+	/*
+	 * Save ID registers for the guest in id_regs[].
+	 * (Op0, Op1, CRn, CRm, Op2) of the ID registers to be saved in it
+	 * is (3, 0, 0, crm, op2), where 1<=crm<8, 0<=op2<8.
+	 */
+#define KVM_ARM_ID_REG_MAX_NUM	56
+#define IDREG_IDX(id)		(((sys_reg_CRm(id) - 1) << 3) | sys_reg_Op2(id))
+	u64 id_regs[KVM_ARM_ID_REG_MAX_NUM];
 };
 
 struct kvm_vcpu_fault_info {
@@ -775,6 +784,8 @@ int kvm_arm_vcpu_arch_has_attr(struct kvm_vcpu *vcpu,
 long kvm_vm_ioctl_mte_copy_tags(struct kvm *kvm,
 				struct kvm_arm_copy_mte_tags *copy_tags);
 
+void set_default_id_regs(struct kvm *kvm);
+
 /* Guest/host FPSIMD coordination helpers */
 int kvm_arch_vcpu_run_map_fp(struct kvm_vcpu *vcpu);
 void kvm_arch_vcpu_load_fp(struct kvm_vcpu *vcpu);
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 523bc934fe2f..04312f7ee0da 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -156,6 +156,7 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
 	kvm->arch.max_vcpus = kvm_arm_default_max_vcpus();
 
 	set_default_spectre(kvm);
+	set_default_id_regs(kvm);
 
 	return ret;
 out_free_stage2_pgd:
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 7b45c040cc27..5b813a0b7b1c 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -33,6 +33,8 @@
 
 #include "trace.h"
 
+static u64 read_id_reg_with_encoding(const struct kvm_vcpu *vcpu, u32 id);
+
 /*
  * All of this file is extremely similar to the ARM coproc.c, but the
  * types are different. My gut feeling is that it should be pretty
@@ -277,7 +279,7 @@ 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 = read_id_reg_with_encoding(vcpu, SYS_ID_AA64MMFR1_EL1);
 	u32 sr = reg_to_encoding(r);
 
 	if (!(val & (0xfUL << ID_AA64MMFR1_LOR_SHIFT))) {
@@ -1102,17 +1104,20 @@ 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)
+/*
+ * Return true if the register's (Op0, Op1, CRn, CRm, Op2) is
+ * (3, 0, 0, crm, op2), where 1<=crm<8, 0<=op2<8.
+ */
+static bool is_id_reg(u32 id)
 {
-	u32 id = reg_to_encoding(r);
-	u64 val;
-
-	if (raz)
-		return 0;
+	return (sys_reg_Op0(id) == 3 && sys_reg_Op1(id) == 0 &&
+		sys_reg_CRn(id) == 0 && sys_reg_CRm(id) >= 1 &&
+		sys_reg_CRm(id) < 8);
+}
 
-	val = read_sanitised_ftr_reg(id);
+static u64 read_id_reg_with_encoding(const struct kvm_vcpu *vcpu, u32 id)
+{
+	u64 val = vcpu->kvm->arch.id_regs[IDREG_IDX(id)];
 
 	switch (id) {
 	case SYS_ID_AA64PFR0_EL1:
@@ -1167,6 +1172,14 @@ static u64 read_id_reg(const struct kvm_vcpu *vcpu,
 	return val;
 }
 
+static u64 read_id_reg(const struct kvm_vcpu *vcpu,
+		       struct sys_reg_desc const *r, bool raz)
+{
+	u32 id = reg_to_encoding(r);
+
+	return raz ? 0 : read_id_reg_with_encoding(vcpu, id);
+}
+
 static unsigned int id_visibility(const struct kvm_vcpu *vcpu,
 				  const struct sys_reg_desc *r)
 {
@@ -1267,9 +1280,8 @@ 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.
+ * For now, these registers are immutable for userspace, so for set_id_reg()
+ * 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,
@@ -1882,8 +1894,8 @@ 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 = read_id_reg_with_encoding(vcpu, SYS_ID_AA64DFR0_EL1);
+		u64 pfr = read_id_reg_with_encoding(vcpu, 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) |
@@ -2895,3 +2907,42 @@ void kvm_sys_reg_table_init(void)
 	/* Clear all higher bits. */
 	cache_levels &= (1 << (i*3))-1;
 }
+
+/*
+ * Set the guest's ID registers that are defined in sys_reg_descs[]
+ * with ID_SANITISED() to the host's sanitized value.
+ */
+void set_default_id_regs(struct kvm *kvm)
+{
+	int i;
+	u32 id;
+	const struct sys_reg_desc *rd;
+	u64 val;
+	struct sys_reg_params params = {
+		Op0(sys_reg_Op0(SYS_ID_PFR0_EL1)),
+		Op1(sys_reg_Op1(SYS_ID_PFR0_EL1)),
+		CRn(sys_reg_CRn(SYS_ID_PFR0_EL1)),
+		CRm(sys_reg_CRm(SYS_ID_PFR0_EL1)),
+		Op2(sys_reg_Op2(SYS_ID_PFR0_EL1)),
+	};
+
+	/*
+	 * Find the first entry of the ID register (ID_PFR0_EL1) from
+	 * sys_reg_descs table, and walk through only the ID register
+	 * entries in the table.
+	 */
+	rd = find_reg(&params, sys_reg_descs, ARRAY_SIZE(sys_reg_descs));
+	for (i = 0; i < KVM_ARM_ID_REG_MAX_NUM; i++, rd++) {
+		id = reg_to_encoding(rd);
+		if (WARN_ON_ONCE(!is_id_reg(id)))
+			/* Shouldn't happen */
+			continue;
+
+		if (rd->access != access_id_reg)
+			/* Hidden or reserved ID register */
+			continue;
+
+		val = read_sanitised_ftr_reg(id);
+		kvm->arch.id_regs[IDREG_IDX(id)] = val;
+	}
+}
-- 
2.36.0.rc0.470.gd361397f0d-goog

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