[PATCH v8 2/6] KVM: arm64: Save ID registers' sanitized value per guest

Jing Zhang jingzhangos at google.com
Wed May 3 10:16:14 PDT 2023


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.

Co-developed-by: Reiji Watanabe <reijiw at google.com>
Signed-off-by: Reiji Watanabe <reijiw at google.com>
Signed-off-by: Jing Zhang <jingzhangos at google.com>
---
 arch/arm64/include/asm/kvm_host.h | 20 ++++++++++++++
 arch/arm64/kvm/arm.c              |  1 +
 arch/arm64/kvm/id_regs.c          | 46 +++++++++++++++++++++++++------
 arch/arm64/kvm/sys_regs.c         | 11 +++++++-
 arch/arm64/kvm/sys_regs.h         |  3 +-
 5 files changed, 69 insertions(+), 12 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index bcd774d74f34..a7d4d9e093e3 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -177,6 +177,21 @@ struct kvm_smccc_features {
 	unsigned long vendor_hyp_bmap;
 };
 
+/*
+ * Emulated CPU ID registers per VM
+ * (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.
+ *
+ * These emulated idregs are VM-wide, but accessed from the context of a vCPU.
+ * Access to id regs are guarded by kvm_arch.config_lock.
+ */
+#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.idregs.regs[IDREG_IDX(id)]
+struct kvm_idregs {
+	u64 regs[KVM_ARM_ID_REG_NUM];
+};
+
 typedef unsigned int pkvm_handle_t;
 
 struct kvm_protected_vm {
@@ -243,6 +258,9 @@ struct kvm_arch {
 	/* Hypercall features firmware registers' descriptor */
 	struct kvm_smccc_features smccc_feat;
 
+	/* Emulated CPU ID registers */
+	struct kvm_idregs idregs;
+
 	/*
 	 * For an untrusted host VM, 'pkvm.handle' is used to lookup
 	 * the associated pKVM instance in the hypervisor.
@@ -1008,6 +1026,8 @@ 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_init_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 4b2e16e696a8..e34744c36406 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_init_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 96b4c43a5100..e769223bcee2 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 = IDREG(vcpu->kvm, 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,
@@ -458,3 +459,30 @@ int emulate_id_reg(struct kvm_vcpu *vcpu, struct sys_reg_params *params)
 
 	return 1;
 }
+
+/*
+ * 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_init_id_regs(struct kvm *kvm)
+{
+	u64 val;
+	u32 id;
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(id_reg_descs); i++) {
+		id = reg_to_encoding(&id_reg_descs[i]);
+
+		/*
+		 * Some hidden ID registers which are not in arm64_ftr_regs[]
+		 * would cause warnings from read_sanitised_ftr_reg().
+		 * Skip those ID registers to avoid the warnings.
+		 */
+		if (id_reg_descs[i].visibility == raz_visibility)
+			/* Hidden or reserved ID register */
+			continue;
+
+		val = read_sanitised_ftr_reg(id);
+		IDREG(kvm, id) = val;
+	}
+}
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 8dba10696dac..2e7b17d14b4f 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -364,7 +364,7 @@ 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))) {
@@ -2967,5 +2967,14 @@ int __init kvm_sys_reg_table_init(void)
 	for (i = 0; i < ARRAY_SIZE(invariant_sys_regs); i++)
 		invariant_sys_regs[i].reset(NULL, &invariant_sys_regs[i]);
 
+	/* Sanity check for ID registers */
+	for (i = 0; i < ARRAY_SIZE(id_reg_descs); i++) {
+		if (!is_id_reg(reg_to_encoding(&id_reg_descs[i]))) {
+			kvm_err("Non-ID register(index:%d, name: %s) found in idregs table!\n",
+				i, id_reg_descs[i].name);
+			return -EINVAL;
+		}
+	}
+
 	return 0;
 }
diff --git a/arch/arm64/kvm/sys_regs.h b/arch/arm64/kvm/sys_regs.h
index 7ce546a8be60..e88fd77309b2 100644
--- a/arch/arm64/kvm/sys_regs.h
+++ b/arch/arm64/kvm/sys_regs.h
@@ -237,6 +237,7 @@ bool write_to_read_only(struct kvm_vcpu *vcpu,
 			struct sys_reg_params *params, const struct sys_reg_desc *r);
 unsigned int raz_visibility(const struct kvm_vcpu *vcpu, const struct sys_reg_desc *r);
 int emulate_id_reg(struct kvm_vcpu *vcpu, struct sys_reg_params *params);
+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
@@ -251,6 +252,4 @@ int emulate_id_reg(struct kvm_vcpu *vcpu, struct sys_reg_params *params);
 	CRn(sys_reg_CRn(reg)), CRm(sys_reg_CRm(reg)),	\
 	Op2(sys_reg_Op2(reg))
 
-#define KVM_ARM_ID_REG_NUM	56
-
 #endif /* __ARM64_KVM_SYS_REGS_LOCAL_H__ */
-- 
2.40.1.495.gc816e09b53d-goog




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