Re: [PATCH v3 2/6] KVM: arm64: Save ID registers' sanitized value per guest

From: Reiji Watanabe <redacted>

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 <redacted>
Co-developed-by: Jing Zhang <redacted>
Signed-off-by: Jing Zhang <redacted>
---
 arch/arm64/include/asm/kvm_host.h | 12 +++++++++
 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, 50 insertions(+), 10 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index a1892a8f6032..5c1cec4efa37 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h

@@ -245,6 +245,16 @@ 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))
+#define IDREG(kvm, id)		kvm->arch.id_regs[IDREG_IDX(id)]

+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_with_encoding(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;