[PATCH v4 2/6] KVM: arm64: Save ID registers' sanitized value per guest

[Jing Zhang]

From: Reiji Watanabe <reijiw at google.com>

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).

No functional change intended.

Signed-off-by: Reiji Watanabe <reijiw at google.com>
Co-developed-by: Jing Zhang <jingzhangos at google.com>
Signed-off-by: Jing Zhang <jingzhangos at google.com>
---
 arch/arm64/include/asm/kvm_host.h | 11 ++++++++
 arch/arm64/kvm/arm.c              |  1 +
 arch/arm64/kvm/id_regs.c          | 44 ++++++++++++++++++++++++-------
 arch/arm64/kvm/sys_regs.c         |  2 +-
 arch/arm64/kvm/sys_regs.h         |  1 +
 5 files changed, 49 insertions(+), 10 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index a1892a8f6032..fb6b50b1f111 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -245,6 +245,15 @@ struct kvm_arch {
 	 * the associated pKVM instance in the hypervisor.
 	 */
 	struct kvm_protected_vm pkvm;
+
+	/*
+	 * 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_NUM	56
+#define IDREG_IDX(id)		(((sys_reg_CRm(id) - 1) << 3) | sys_reg_Op2(id))
+	u64 id_regs[KVM_ARM_ID_REG_NUM];
 };
 
 struct kvm_vcpu_fault_info {
@@ -1005,6 +1014,8 @@ 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 kvm_arm_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 3bd732eaf087..4579c878ab30 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -153,6 +153,7 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
 
 	set_default_spectre(kvm);
 	kvm_arm_init_hypercalls(kvm);
+	kvm_arm_set_default_id_regs(kvm);
 
 	/*
 	 * Initialise the default PMUver before there is a chance to
diff --git a/arch/arm64/kvm/id_regs.c b/arch/arm64/kvm/id_regs.c
index 08b738852955..e393b5730557 100644
--- a/arch/arm64/kvm/id_regs.c
+++ b/arch/arm64/kvm/id_regs.c
@@ -52,16 +52,9 @@ static u8 pmuver_to_perfmon(u8 pmuver)
 	}
 }
 
-/* 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)
+u64 kvm_arm_read_id_reg(const struct kvm_vcpu *vcpu, u32 id)
 {
-	u32 id = reg_to_encoding(r);
-	u64 val;
-
-	if (sysreg_visible_as_raz(vcpu, r))
-		return 0;
-
-	val = read_sanitised_ftr_reg(id);
+	u64 val = vcpu->kvm->arch.id_regs[IDREG_IDX(id)];
 
 	switch (id) {
 	case SYS_ID_AA64PFR0_EL1:
@@ -126,6 +119,14 @@ static u64 read_id_reg(const struct kvm_vcpu *vcpu, struct sys_reg_desc const *r
 	return val;
 }
 
+static u64 read_id_reg(const struct kvm_vcpu *vcpu, struct sys_reg_desc const *r)
+{
+	if (sysreg_visible_as_raz(vcpu, r))
+		return 0;
+
+	return kvm_arm_read_id_reg(vcpu, reg_to_encoding(r));
+}
+
 /* cpufeature ID register access trap handlers */
 
 static bool access_id_reg(struct kvm_vcpu *vcpu,
@@ -504,3 +505,28 @@ int kvm_arm_walk_id_regs(struct kvm_vcpu *vcpu, u64 __user *uind)
 	}
 	return total;
 }
+
+/*
+ * Set the guest's ID registers that are defined in id_reg_descs[]
+ * with ID_SANITISED() to the host's sanitized value.
+ */
+void kvm_arm_set_default_id_regs(struct kvm *kvm)
+{
+	int i;
+	u32 id;
+	u64 val;
+
+	for (i = 0; i < ARRAY_SIZE(id_reg_descs); i++) {
+		id = reg_to_encoding(&id_reg_descs[i]);
+		if (WARN_ON_ONCE(!is_id_reg(id)))
+			/* Shouldn't happen */
+			continue;
+
+		if (id_reg_descs[i].visibility == raz_visibility)
+			/* Hidden or reserved ID register */
+			continue;
+
+		val = read_sanitised_ftr_reg(id);
+		kvm->arch.id_regs[IDREG_IDX(id)] = val;
+	}
+}
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 22b60474fcab..3243c924527e 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -354,7 +354,7 @@ 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 = kvm_arm_read_id_reg(vcpu, SYS_ID_AA64MMFR1_EL1);
 	u32 sr = reg_to_encoding(r);
 
 	if (!(val & (0xfUL << ID_AA64MMFR1_EL1_LO_SHIFT))) {
diff --git a/arch/arm64/kvm/sys_regs.h b/arch/arm64/kvm/sys_regs.h
index ad41305348f7..ee136ba28fa5 100644
--- a/arch/arm64/kvm/sys_regs.h
+++ b/arch/arm64/kvm/sys_regs.h
@@ -261,6 +261,7 @@ int kvm_arm_get_id_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg);
 int kvm_arm_set_id_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg);
 bool kvm_arm_check_idreg_table(void);
 int kvm_arm_walk_id_regs(struct kvm_vcpu *vcpu, u64 __user *uind);
+u64 kvm_arm_read_id_reg(const struct kvm_vcpu *vcpu, u32 id);
 
 #define AA32(_x)	.aarch32_map = AA32_##_x
 #define Op0(_x) 	.Op0 = _x
-- 
2.40.0.rc1.284.g88254d51c5-goog