diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index 17811002a8f7cdf54fb065e2b65a60472f2f6d3e..392b4ac81af92d890e218b0e004c6646644cb68c 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -3428,6 +3428,8 @@ return indicates the attribute is implemented.  It does not necessarily
 indicate that the attribute can be read or written in the device's
 current state.  "addr" is ignored.
 
+.. _KVM_ARM_VCPU_INIT:
+
 4.82 KVM_ARM_VCPU_INIT
 ----------------------
 
@@ -6128,6 +6130,56 @@ writes to the CNTVCT_EL0 and CNTPCT_EL0 registers using the SET_ONE_REG
 interface. No error will be returned, but the resulting offset will not be
 applied.
 
+.. _KVM_ARM_GET_REG_WRITABLE_MASKS:
+
+4.139 KVM_ARM_GET_REG_WRITABLE_MASKS
+-------------------------------------------
+
+:Capability: KVM_CAP_ARM_SUPPORTED_REG_MASK_RANGES
+:Architectures: arm64
+:Type: vm ioctl
+:Parameters: struct reg_mask_range (in/out)
+:Returns: 0 on success, < 0 on error
+
+
+::
+
+        #define KVM_ARM_FEATURE_ID_RANGE	0
+        #define KVM_ARM_FEATURE_ID_RANGE_SIZE	(3 * 8 * 8)
+
+        struct reg_mask_range {
+                __u64 addr;             /* Pointer to mask array */
+                __u32 range;            /* Requested range */
+                __u32 reserved[13];
+        };
+
+This ioctl copies the writable masks for a selected range of registers to
+userspace.
+
+The ``addr`` field is a pointer to the destination array where KVM copies
+the writable masks.
+
+The ``range`` field indicates the requested range of registers.
+``KVM_CHECK_EXTENSION`` for the ``KVM_CAP_ARM_SUPPORTED_REG_MASK_RANGES``
+capability returns the supported ranges, expressed as a set of flags. Each
+flag's bit index represents a possible value for the ``range`` field.
+All other values are reserved for future use and KVM may return an error.
+
+The ``reserved[13]`` array is reserved for future use and should be 0, or
+KVM may return an error.
+
+KVM_ARM_FEATURE_ID_RANGE (0)
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+The Feature ID range is defined as the AArch64 System register space with
+op0==3, op1=={0, 1, 3}, CRn==0, CRm=={0-7}, op2=={0-7}.
+
+The mask returned array pointed to by ``addr`` is indexed by the macro
+``ARM64_FEATURE_ID_RANGE_IDX(op0, op1, crn, crm, op2)``, allowing userspace
+to know what fields can be changed for the system register described by
+``op0, op1, crn, crm, op2``. KVM rejects ID register values that describe a
+superset of the features supported by the system.
+
 5. The kvm_run structure
 ========================
 
diff --git a/Documentation/virt/kvm/arm/index.rst b/Documentation/virt/kvm/arm/index.rst
index e84848432158084f789b0c18764afd1f3fb547ac..7f231c724e16756f63b2a38e9e2df6a60727d2ee 100644
--- a/Documentation/virt/kvm/arm/index.rst
+++ b/Documentation/virt/kvm/arm/index.rst
@@ -11,3 +11,4 @@ ARM
    hypercalls
    pvtime
    ptp_kvm
+   vcpu-features
diff --git a/Documentation/virt/kvm/arm/vcpu-features.rst b/Documentation/virt/kvm/arm/vcpu-features.rst
new file mode 100644
index 0000000000000000000000000000000000000000..f7cc6d8d8b74052616acbf0dab3b92ec13badf22
--- /dev/null
+++ b/Documentation/virt/kvm/arm/vcpu-features.rst
@@ -0,0 +1,48 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+===============================
+vCPU feature selection on arm64
+===============================
+
+KVM/arm64 provides two mechanisms that allow userspace to configure
+the CPU features presented to the guest.
+
+KVM_ARM_VCPU_INIT
+=================
+
+The ``KVM_ARM_VCPU_INIT`` ioctl accepts a bitmap of feature flags
+(``struct kvm_vcpu_init::features``). Features enabled by this interface are
+*opt-in* and may change/extend UAPI. See :ref:`KVM_ARM_VCPU_INIT` for complete
+documentation of the features controlled by the ioctl.
+
+Otherwise, all CPU features supported by KVM are described by the architected
+ID registers.
+
+The ID Registers
+================
+
+The Arm architecture specifies a range of *ID Registers* that describe the set
+of architectural features supported by the CPU implementation. KVM initializes
+the guest's ID registers to the maximum set of CPU features supported by the
+system. The ID register values may be VM-scoped in KVM, meaning that the
+values could be shared for all vCPUs in a VM.
+
+KVM allows userspace to *opt-out* of certain CPU features described by the ID
+registers by writing values to them via the ``KVM_SET_ONE_REG`` ioctl. The ID
+registers are mutable until the VM has started, i.e. userspace has called
+``KVM_RUN`` on at least one vCPU in the VM. Userspace can discover what fields
+are mutable in the ID registers using the ``KVM_ARM_GET_REG_WRITABLE_MASKS``.
+See the :ref:`ioctl documentation <KVM_ARM_GET_REG_WRITABLE_MASKS>` for more
+details.
+
+Userspace is allowed to *limit* or *mask* CPU features according to the rules
+outlined by the architecture in DDI0487J.a D19.1.3 'Principles of the ID
+scheme for fields in ID register'. KVM does not allow ID register values that
+exceed the capabilities of the system.
+
+.. warning::
+   It is **strongly recommended** that userspace modify the ID register values
+   before accessing the rest of the vCPU's CPU register state. KVM may use the
+   ID register values to control feature emulation. Interleaving ID register
+   modification with other system register accesses may lead to unpredictable
+   behavior.
diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
index d68307a50d13ec2c98e162e6809bd4dd670f1bec..683ebd5b7e962ccafcb7d8050e3b22322a933a76 100644
--- a/arch/arm64/include/asm/cpufeature.h
+++ b/arch/arm64/include/asm/cpufeature.h
@@ -651,6 +651,20 @@ static inline bool cpu_supports_mixed_endian_el0(void)
 	return id_aa64mmfr0_mixed_endian_el0(read_cpuid(ID_AA64MMFR0_EL1));
 }
 
+static inline bool supports_cnp(int scope)
+{
+	u64 mmfr2;
+	u8 cnp;
+
+	if (scope == SCOPE_LOCAL_CPU)
+		mmfr2 = read_sysreg_s(SYS_ID_AA64MMFR2_EL1);
+	else
+		mmfr2 = read_sanitised_ftr_reg(SYS_ID_AA64MMFR2_EL1);
+
+	cnp = cpuid_feature_extract_unsigned_field(mmfr2,
+							ID_AA64MMFR2_EL1_CnP_SHIFT);
+	return cnp == 1;
+}
 
 static inline bool supports_csv2p3(int scope)
 {
diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
index f0b10cb2c87dd1a9cd67cc3e641d6a6324a8e19c..79c4a62de5c46e3622d650fdadb611375296f25c 100644
--- a/arch/arm64/include/asm/kvm_emulate.h
+++ b/arch/arm64/include/asm/kvm_emulate.h
@@ -91,7 +91,8 @@ static inline void vcpu_reset_hcr(struct kvm_vcpu *vcpu)
 	}
 
 	if (cpus_have_final_cap(ARM64_HAS_EVT) &&
-	    !cpus_have_final_cap(ARM64_MISMATCHED_CACHE_TYPE))
+	    !cpus_have_final_cap(ARM64_MISMATCHED_CACHE_TYPE) &&
+	    kvm_read_vm_id_reg(vcpu->kvm, SYS_CTR_EL0) == read_sanitised_ftr_reg(SYS_CTR_EL0))
 		vcpu->arch.hcr_el2 |= HCR_TID4;
 	else
 		vcpu->arch.hcr_el2 |= HCR_TID2;
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index ac4e59256f8ed5c6294208bb6f80cfc2293b2db4..9ffdea9d59247fefbe19630c4b507ce608f210d2 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -298,6 +298,10 @@ struct kvm_arch {
 	};
 	bool is_virtcca_cvm;
 #endif
+
+#ifndef __GENKSYMS__
+	u64 ctr_el0;
+#endif
 };
 
 struct kvm_vcpu_fault_info {
@@ -1202,6 +1206,8 @@ int kvm_vm_ioctl_mte_copy_tags(struct kvm *kvm,
 			       struct kvm_arm_copy_mte_tags *copy_tags);
 int kvm_vm_ioctl_set_counter_offset(struct kvm *kvm,
 				    struct kvm_arm_counter_offset *offset);
+int kvm_vm_ioctl_get_reg_writable_masks(struct kvm *kvm,
+					struct reg_mask_range *range);
 
 /* Guest/host FPSIMD coordination helpers */
 int kvm_arch_vcpu_run_map_fp(struct kvm_vcpu *vcpu);
@@ -1283,6 +1289,24 @@ extern unsigned int twedel;
 void kvm_arm_vcpu_power_off(struct kvm_vcpu *vcpu);
 bool kvm_arm_vcpu_stopped(struct kvm_vcpu *vcpu);
 
+static inline u64 *__vm_id_reg(struct kvm_arch *ka, u32 reg)
+{
+	switch (reg) {
+	case sys_reg(3, 0, 0, 1, 0) ... sys_reg(3, 0, 0, 7, 7):
+		return &ka->id_regs[IDREG_IDX(reg)];
+	case SYS_CTR_EL0:
+		return &ka->ctr_el0;
+	default:
+		WARN_ON_ONCE(1);
+		return NULL;
+	}
+}
+
+#define kvm_read_vm_id_reg(kvm, reg)					\
+	({ u64 __val = *__vm_id_reg(&(kvm)->arch, reg); __val; })
+
+void kvm_set_vm_id_reg(struct kvm *kvm, u32 reg, u64 val);
+
 extern bool force_wfi_trap;
 extern bool kvm_ncsnp_support;
 extern bool kvm_dvmbm_support;
diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h
index 97941e582d83d0d0189d6a482a588290ac54df69..03b0278568187ea457aa08670d269593cefd48e2 100644
--- a/arch/arm64/include/uapi/asm/kvm.h
+++ b/arch/arm64/include/uapi/asm/kvm.h
@@ -509,6 +509,38 @@ struct kvm_smccc_filter {
 #define KVM_HYPERCALL_EXIT_SMC		(1U << 0)
 #define KVM_HYPERCALL_EXIT_16BIT	(1U << 1)
 
+/*
+ * Get feature ID registers userspace writable mask.
+ *
+ * From DDI0487J.a, D19.2.66 ("ID_AA64MMFR2_EL1, AArch64 Memory Model
+ * Feature Register 2"):
+ *
+ * "The Feature ID space is defined as the System register space in
+ * AArch64 with op0==3, op1=={0, 1, 3}, CRn==0, CRm=={0-7},
+ * op2=={0-7}."
+ *
+ * This covers all currently known R/O registers that indicate
+ * anything useful feature wise, including the ID registers.
+ *
+ * If we ever need to introduce a new range, it will be described as
+ * such in the range field.
+ */
+#define KVM_ARM_FEATURE_ID_RANGE_IDX(op0, op1, crn, crm, op2)		\
+	({								\
+		__u64 __op1 = (op1) & 3;				\
+		__op1 -= (__op1 == 3);					\
+		(__op1 << 6 | ((crm) & 7) << 3 | (op2));		\
+	})
+
+#define KVM_ARM_FEATURE_ID_RANGE	0
+#define KVM_ARM_FEATURE_ID_RANGE_SIZE	(3 * 8 * 8)
+
+struct reg_mask_range {
+	__u64 addr;		/* Pointer to mask array */
+	__u32 range;		/* Requested range */
+	__u32 reserved[13];
+};
+
 #endif
 
 #endif /* __ARM_KVM_H__ */
diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c
index 2e5e4052a182e5ff30fb639de87c715c57467ddf..5dc7c36e5820caa3fb3a1bcaaab5d60bae8a9128 100644
--- a/arch/arm64/kernel/cpu_errata.c
+++ b/arch/arm64/kernel/cpu_errata.c
@@ -60,6 +60,15 @@ is_kryo_midr(const struct arm64_cpu_capabilities *entry, int scope)
 	return model == entry->midr_range.model;
 }
 
+#ifdef CONFIG_HISILICON_ERRATUM_162100125
+static bool
+hisilicon_162100125_match(const struct arm64_cpu_capabilities *entry,
+			int scope)
+{
+	return is_affected_midr_range_list(entry, scope) && supports_cnp(scope);
+}
+#endif
+
 #ifdef CONFIG_HISILICON_ERRATUM_1980005
 static bool
 hisilicon_1980005_match(const struct arm64_cpu_capabilities *entry,
@@ -639,7 +648,9 @@ const struct arm64_cpu_capabilities arm64_errata[] = {
 	{
 		.desc = "Hisilicon erratum 162100125",
 		.capability = ARM64_WORKAROUND_HISILICON_ERRATUM_162100125,
-		ERRATA_MIDR_RANGE_LIST(hisilicon_erratum_162100125_cpus),
+		.matches = hisilicon_162100125_match,
+		.type = ARM64_CPUCAP_LOCAL_CPU_ERRATUM,
+		.midr_range_list = hisilicon_erratum_162100125_cpus,
 	},
 #endif
 #ifdef CONFIG_HISILICON_ERRATUM_1980005
diff --git a/arch/arm64/kernel/proton-pack.c b/arch/arm64/kernel/proton-pack.c
index 4bca7ad7b5e336e5ea3d25411629e509a5d5be29..6b62a9776850447e0b8e98cfe2b685f9189037ca 100644
--- a/arch/arm64/kernel/proton-pack.c
+++ b/arch/arm64/kernel/proton-pack.c
@@ -865,6 +865,7 @@ u8 spectre_bhb_loop_affected(int scope)
 		static const struct midr_range spectre_bhb_k24_list[] = {
 			MIDR_ALL_VERSIONS(MIDR_CORTEX_A76),
 			MIDR_ALL_VERSIONS(MIDR_CORTEX_A77),
+			MIDR_ALL_VERSIONS(MIDR_HISI_LINXICORE9100),
 			MIDR_ALL_VERSIONS(MIDR_NEOVERSE_N1),
 			{},
 		};
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index c0126a9203ae7641257fa5d3b8a443d8abd2f0c4..48cb623f8549f6274126c4f188595f7bd52dea1c 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -436,6 +436,9 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 		r = static_key_enabled(&virtcca_cvm_is_available);
 		break;
 #endif
+	case KVM_CAP_ARM_SUPPORTED_REG_MASK_RANGES:
+		r = BIT(0);
+		break;
 	default:
 		r = 0;
 	}
@@ -1897,6 +1900,13 @@ int kvm_arch_vm_ioctl(struct file *filp, unsigned int ioctl, unsigned long arg)
 		return 0;
 	}
 #endif
+	case KVM_ARM_GET_REG_WRITABLE_MASKS: {
+		struct reg_mask_range range;
+
+		if (copy_from_user(&range, argp, sizeof(range)))
+			return -EFAULT;
+		return kvm_vm_ioctl_get_reg_writable_masks(kvm, &range);
+	}
 	default:
 		return -EINVAL;
 	}
diff --git a/arch/arm64/kvm/pmu-emul.c b/arch/arm64/kvm/pmu-emul.c
index 6469a7c51df3fdc74f0cee74cc3d2ef4ea8b7fb8..ea715ab0d5a6befad2049a73ed09a7ce2d0aaf9c 100644
--- a/arch/arm64/kvm/pmu-emul.c
+++ b/arch/arm64/kvm/pmu-emul.c
@@ -55,7 +55,7 @@ static u32 __kvm_pmu_event_mask(unsigned int pmuver)
 
 static u32 kvm_pmu_event_mask(struct kvm *kvm)
 {
-	u64 dfr0 = IDREG(kvm, SYS_ID_AA64DFR0_EL1);
+	u64 dfr0 = kvm_read_vm_id_reg(kvm, SYS_ID_AA64DFR0_EL1);
 	u8 pmuver = SYS_FIELD_GET(ID_AA64DFR0_EL1, PMUVer, dfr0);
 
 	return __kvm_pmu_event_mask(pmuver);
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 0cfa8d93e2ee36ecb14b1db62db3b25a3c8db299..cb31964c95c4978c6093188c26d413c2e9deffdc 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -385,7 +385,7 @@ 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 = IDREG(vcpu->kvm, SYS_ID_AA64MMFR1_EL1);
 	u32 sr = reg_to_encoding(r);
 
 	if (!(val & (0xfUL << ID_AA64MMFR1_EL1_LO_SHIFT))) {
@@ -1247,8 +1247,14 @@ static s64 kvm_arm64_ftr_safe_value(u32 id, const struct arm64_ftr_bits *ftrp,
 	/* Some features have different safe value type in KVM than host features */
 	switch (id) {
 	case SYS_ID_AA64DFR0_EL1:
-		if (kvm_ftr.shift == ID_AA64DFR0_EL1_PMUVer_SHIFT)
+		switch (kvm_ftr.shift) {
+		case ID_AA64DFR0_EL1_PMUVer_SHIFT:
 			kvm_ftr.type = FTR_LOWER_SAFE;
+			break;
+		case ID_AA64DFR0_EL1_DebugVer_SHIFT:
+			kvm_ftr.type = FTR_LOWER_SAFE;
+			break;
+		}
 		break;
 	case SYS_ID_DFR0_EL1:
 		if (kvm_ftr.shift == ID_DFR0_EL1_PerfMon_SHIFT)
@@ -1357,6 +1363,12 @@ static u64 __kvm_read_sanitised_id_reg(const struct kvm_vcpu *vcpu,
 		val &= ~ARM64_FEATURE_MASK(ID_AA64PFR1_EL1_SME);
 		val &= ~ARM64_FEATURE_MASK(ID_AA64PFR1_EL1_NMI);
 		val |= FIELD_PREP(ARM64_FEATURE_MASK(ID_AA64PFR1_EL1_NMI), vcpu->kvm->arch.pfr1_nmi);
+		/*
+		 * MPAM is disabled by default as KVM also needs a set of PARTID to
+		 * program the MPAMVPMx_EL2 PARTID remapping registers with. Hide,
+		 * MPAM_frac as well from Guest to handle FEAT_MPAMv0p1.
+		 */
+		val &= ~ARM64_FEATURE_MASK(ID_AA64PFR1_EL1_MPAM_frac);
 		break;
 	case SYS_ID_AA64ISAR1_EL1:
 		if (!vcpu_has_ptrauth(vcpu))
@@ -1392,7 +1404,7 @@ static u64 kvm_read_sanitised_id_reg(struct kvm_vcpu *vcpu,
 
 static u64 read_id_reg(const struct kvm_vcpu *vcpu, const struct sys_reg_desc *r)
 {
-	return IDREG(vcpu->kvm, reg_to_encoding(r));
+	return kvm_read_vm_id_reg(vcpu->kvm, reg_to_encoding(r));
 }
 
 /*
@@ -1401,11 +1413,21 @@ static u64 read_id_reg(const struct kvm_vcpu *vcpu, const struct sys_reg_desc *r
  */
 static inline bool is_id_reg(u32 id)
 {
+	if (id == SYS_CTR_EL0)
+		return true;
+
 	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);
 }
 
+static inline bool is_aa32_id_reg(u32 id)
+{
+	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) <= 3);
+}
+
 static unsigned int id_visibility(const struct kvm_vcpu *vcpu,
 				  const struct sys_reg_desc *r)
 {
@@ -1499,17 +1521,31 @@ static u64 read_sanitised_id_aa64pfr0_el1(struct kvm_vcpu *vcpu,
 
 	val &= ~ID_AA64PFR0_EL1_AMU_MASK;
 
+	/*
+	 * MPAM is disabled by default as KVM also needs a set of PARTID to
+	 * program the MPAMVPMx_EL2 PARTID remapping registers with. But some
+	 * older kernels let the guest see the ID bit.
+	 */
+	val &= ~ID_AA64PFR0_EL1_MPAM_MASK;
+
 	return val;
 }
 
+#define ID_REG_LIMIT_FIELD_ENUM(val, reg, field, limit)			       \
+({									       \
+	u64 __f_val = FIELD_GET(reg##_##field##_MASK, val);		       \
+	(val) &= ~reg##_##field##_MASK;					       \
+	(val) |= FIELD_PREP(reg##_##field##_MASK,			       \
+			min(__f_val, (u64)reg##_##field##_##limit));	       \
+	(val);								       \
+})
+
 static u64 read_sanitised_id_aa64dfr0_el1(struct kvm_vcpu *vcpu,
 					  const struct sys_reg_desc *rd)
 {
 	u64 val = read_sanitised_ftr_reg(SYS_ID_AA64DFR0_EL1);
 
-	/* Limit debug to ARMv8.0 */
-	val &= ~ID_AA64DFR0_EL1_DebugVer_MASK;
-	val |= SYS_FIELD_PREP_ENUM(ID_AA64DFR0_EL1, DebugVer, IMP);
+	val = ID_REG_LIMIT_FIELD_ENUM(val, ID_AA64DFR0_EL1, DebugVer, V8P8);
 
 	/*
 	 * Only initialize the PMU version if the vCPU was configured with one.
@@ -1532,6 +1568,7 @@ static int set_id_aa64dfr0_el1(struct kvm_vcpu *vcpu,
 			       const struct sys_reg_desc *rd,
 			       u64 val)
 {
+	u8 debugver = SYS_FIELD_GET(ID_AA64DFR0_EL1, DebugVer, val);
 	u8 pmuver = SYS_FIELD_GET(ID_AA64DFR0_EL1, PMUVer, val);
 
 	/*
@@ -1551,9 +1588,39 @@ static int set_id_aa64dfr0_el1(struct kvm_vcpu *vcpu,
 	if (pmuver == ID_AA64DFR0_EL1_PMUVer_IMP_DEF)
 		val &= ~ID_AA64DFR0_EL1_PMUVer_MASK;
 
+	/*
+	 * ID_AA64DFR0_EL1.DebugVer is one of those awkward fields with a
+	 * nonzero minimum safe value.
+	 */
+	if (debugver < ID_AA64DFR0_EL1_DebugVer_IMP)
+		return -EINVAL;
+
 	return set_id_reg(vcpu, rd, val);
 }
 
+static int set_id_aa64pfr0_el1(struct kvm_vcpu *vcpu,
+			       const struct sys_reg_desc *rd, u64 user_val)
+{
+	u64 hw_val = read_sanitised_ftr_reg(SYS_ID_AA64PFR0_EL1);
+	u64 mpam_mask = ID_AA64PFR0_EL1_MPAM_MASK;
+
+	/*
+	 * Commit 011e5f5bf529f ("arm64/cpufeature: Add remaining feature bits
+	 * in ID_AA64PFR0 register") exposed the MPAM field of AA64PFR0_EL1 to
+	 * guests, but didn't add trap handling. KVM doesn't support MPAM and
+	 * always returns an UNDEF for these registers. The guest must see 0
+	 * for this field.
+	 *
+	 * But KVM must also accept values from user-space that were provided
+	 * by KVM. On CPUs that support MPAM, permit user-space to write
+	 * the santisied value to ID_AA64PFR0_EL1.MPAM, but ignore this field.
+	 */
+	if ((hw_val & mpam_mask) == (user_val & mpam_mask))
+		user_val &= ~ID_AA64PFR0_EL1_MPAM_MASK;
+
+	return set_id_reg(vcpu, rd, user_val);
+}
+
 static u64 read_sanitised_id_dfr0_el1(struct kvm_vcpu *vcpu,
 				      const struct sys_reg_desc *rd)
 {
@@ -1564,6 +1631,8 @@ static u64 read_sanitised_id_dfr0_el1(struct kvm_vcpu *vcpu,
 	if (kvm_vcpu_has_pmu(vcpu))
 		val |= SYS_FIELD_PREP(ID_DFR0_EL1, PerfMon, perfmon);
 
+	val = ID_REG_LIMIT_FIELD_ENUM(val, ID_DFR0_EL1, CopDbg, Debugv8p8);
+
 	return val;
 }
 
@@ -1572,6 +1641,7 @@ static int set_id_dfr0_el1(struct kvm_vcpu *vcpu,
 			   u64 val)
 {
 	u8 perfmon = SYS_FIELD_GET(ID_DFR0_EL1, PerfMon, val);
+	u8 copdbg = SYS_FIELD_GET(ID_DFR0_EL1, CopDbg, val);
 
 	if (perfmon == ID_DFR0_EL1_PerfMon_IMPDEF) {
 		val &= ~ID_DFR0_EL1_PerfMon_MASK;
@@ -1587,6 +1657,9 @@ static int set_id_dfr0_el1(struct kvm_vcpu *vcpu,
 	if (perfmon != 0 && perfmon < ID_DFR0_EL1_PerfMon_PMUv3)
 		return -EINVAL;
 
+	if (copdbg < ID_DFR0_EL1_CopDbg_Armv8)
+		return -EINVAL;
+
 	return set_id_reg(vcpu, rd, val);
 }
 
@@ -1594,6 +1667,8 @@ static int set_id_aa64pfr1_el1(struct kvm_vcpu *vcpu,
 			       const struct sys_reg_desc *rd,
 			       u64 val)
 {
+	u64 hw_val = read_sanitised_ftr_reg(SYS_ID_AA64PFR1_EL1);
+	u64 mpamfrac_mask = ID_AA64PFR1_EL1_MPAM_frac_MASK;
 	u8 nmi;
 
 	nmi = cpuid_feature_extract_unsigned_field(val, ID_AA64PFR1_EL1_NMI_SHIFT);
@@ -1601,15 +1676,23 @@ static int set_id_aa64pfr1_el1(struct kvm_vcpu *vcpu,
 	    (nmi && (!cpus_have_const_cap(ARM64_HAS_NMI) || static_branch_unlikely(&vgic_v3_cpuif_trap))))
 		return -EINVAL;
 
-	/* We can only differ with NMI, and anything else is an error */
-	val ^= read_id_reg(vcpu, rd);
-	val &= ~ARM64_FEATURE_MASK(ID_AA64PFR1_EL1_NMI);
-	if (val)
-		return -EINVAL;
-
 	vcpu->kvm->arch.pfr1_nmi = nmi;
 
-	return 0;
+	/*
+	 * KVM doesn't support MPAM but Commit 14e270fa5c4c ("arm64/cpufeature:
+	 * Add remaining feature bits in ID_AA64PFR1 register") exposed the
+	 * MPAM_frac field of AA64PFR1_EL1 to guests.Though we already hide
+	 * MPAM in ID_AA64PFR0_EL1, need to hide this MPAM_frac field as well
+	 * in order to take of systems with FEAT_MPAMv0p1 support.
+	 *
+	 * Similar to MPAM field in ID_AA64PFR0_EL1, on CPUs that support
+	 * FEAT_MPAMv0p1, permit user-space to write the santisied value to
+	 * ID_AA64PFR1_EL1.MPAM_frac, but ignore this field.
+	 */
+	if ((hw_val & mpamfrac_mask) == (val & mpamfrac_mask))
+		val &= ~ID_AA64PFR1_EL1_MPAM_frac_MASK;
+
+	return set_id_reg(vcpu, rd, val);
 }
 
 /*
@@ -1662,7 +1745,7 @@ static int set_id_reg(struct kvm_vcpu *vcpu, const struct sys_reg_desc *rd,
 
 	ret = arm64_check_features(vcpu, rd, val);
 	if (!ret)
-		IDREG(vcpu->kvm, id) = val;
+		kvm_set_vm_id_reg(vcpu->kvm, id, val);
 
 	mutex_unlock(&vcpu->kvm->arch.config_lock);
 
@@ -1678,6 +1761,18 @@ static int set_id_reg(struct kvm_vcpu *vcpu, const struct sys_reg_desc *rd,
 	return ret;
 }
 
+void kvm_set_vm_id_reg(struct kvm *kvm, u32 reg, u64 val)
+{
+	u64 *p = __vm_id_reg(&kvm->arch, reg);
+
+	lockdep_assert_held(&kvm->arch.config_lock);
+
+	if (KVM_BUG_ON(kvm_vm_has_ran_once(kvm) || !p, kvm))
+		return;
+
+	*p = val;
+}
+
 static int get_raz_reg(struct kvm_vcpu *vcpu, const struct sys_reg_desc *rd,
 		       u64 *val)
 {
@@ -1697,7 +1792,7 @@ static bool access_ctr(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
 	if (p->is_write)
 		return write_to_read_only(vcpu, p, r);
 
-	p->regval = read_sanitised_ftr_reg(SYS_CTR_EL0);
+	p->regval = kvm_read_vm_id_reg(vcpu->kvm, SYS_CTR_EL0);
 	return true;
 }
 
@@ -1875,11 +1970,14 @@ static unsigned int elx2_visibility(const struct kvm_vcpu *vcpu,
  * from userspace.
  */
 
-/* sys_reg_desc initialiser for known cpufeature ID registers */
-#define ID_SANITISED(name) {			\
+#define ID_DESC(name)				\
 	SYS_DESC(SYS_##name),			\
 	.access	= access_id_reg,		\
-	.get_user = get_id_reg,			\
+	.get_user = get_id_reg			\
+
+/* sys_reg_desc initialiser for known cpufeature ID registers */
+#define ID_SANITISED(name) {			\
+	ID_DESC(name),				\
 	.set_user = set_id_reg,			\
 	.visibility = id_visibility,		\
 	.reset = kvm_read_sanitised_id_reg,	\
@@ -1888,15 +1986,22 @@ static unsigned int elx2_visibility(const struct kvm_vcpu *vcpu,
 
 /* sys_reg_desc initialiser for known cpufeature ID registers */
 #define AA32_ID_SANITISED(name) {		\
-	SYS_DESC(SYS_##name),			\
-	.access	= access_id_reg,		\
-	.get_user = get_id_reg,			\
+	ID_DESC(name),				\
 	.set_user = set_id_reg,			\
 	.visibility = aa32_id_visibility,	\
 	.reset = kvm_read_sanitised_id_reg,	\
 	.val = 0,				\
 }
 
+/* sys_reg_desc initialiser for writable ID registers */
+#define ID_WRITABLE(name, mask) {		\
+	ID_DESC(name),				\
+	.set_user = set_id_reg,			\
+	.visibility = id_visibility,		\
+	.reset = kvm_read_sanitised_id_reg,	\
+	.val = mask,				\
+}
+
 /*
  * sys_reg_desc initialiser for architecturally unallocated cpufeature ID
  * register with encoding Op0=3, Op1=0, CRn=0, CRm=crm, Op2=op2
@@ -1918,9 +2023,7 @@ static unsigned int elx2_visibility(const struct kvm_vcpu *vcpu,
  * RAZ for the guest.
  */
 #define ID_HIDDEN(name) {			\
-	SYS_DESC(SYS_##name),			\
-	.access = access_id_reg,		\
-	.get_user = get_id_reg,			\
+	ID_DESC(name),				\
 	.set_user = set_id_reg,			\
 	.visibility = raz_visibility,		\
 	.reset = kvm_read_sanitised_id_reg,	\
@@ -2089,7 +2192,8 @@ static const struct sys_reg_desc sys_reg_descs[] = {
 	  .set_user = set_id_dfr0_el1,
 	  .visibility = aa32_id_visibility,
 	  .reset = read_sanitised_id_dfr0_el1,
-	  .val = ID_DFR0_EL1_PerfMon_MASK, },
+	  .val = ID_DFR0_EL1_PerfMon_MASK |
+		 ID_DFR0_EL1_CopDbg_MASK, },
 	ID_HIDDEN(ID_AFR0_EL1),
 	AA32_ID_SANITISED(ID_MMFR0_EL1),
 	AA32_ID_SANITISED(ID_MMFR1_EL1),
@@ -2121,15 +2225,21 @@ static const struct sys_reg_desc sys_reg_descs[] = {
 	{ SYS_DESC(SYS_ID_AA64PFR0_EL1),
 	  .access = access_id_reg,
 	  .get_user = get_id_reg,
-	  .set_user = set_id_reg,
+	  .set_user = set_id_aa64pfr0_el1,
 	  .reset = read_sanitised_id_aa64pfr0_el1,
-	  .val = ID_AA64PFR0_EL1_CSV2_MASK | ID_AA64PFR0_EL1_CSV3_MASK, },
+	  .val = ~(ID_AA64PFR0_EL1_AMU |
+		   ID_AA64PFR0_EL1_MPAM |
+		   ID_AA64PFR0_EL1_SVE |
+		   ID_AA64PFR0_EL1_RAS |
+		   ID_AA64PFR0_EL1_GIC |
+		   ID_AA64PFR0_EL1_AdvSIMD |
+		   ID_AA64PFR0_EL1_FP), },
 	{ SYS_DESC(SYS_ID_AA64PFR1_EL1), .access = access_id_reg,
 	  .get_user = get_id_reg, .set_user = set_id_aa64pfr1_el1,
 	  .reset = kvm_read_sanitised_id_reg, },
 	ID_UNALLOCATED(4,2),
 	ID_UNALLOCATED(4,3),
-	ID_SANITISED(ID_AA64ZFR0_EL1),
+	ID_WRITABLE(ID_AA64ZFR0_EL1, ~ID_AA64ZFR0_EL1_RES0),
 	ID_HIDDEN(ID_AA64SMFR0_EL1),
 	ID_UNALLOCATED(4,6),
 	ID_UNALLOCATED(4,7),
@@ -2140,7 +2250,22 @@ static const struct sys_reg_desc sys_reg_descs[] = {
 	  .get_user = get_id_reg,
 	  .set_user = set_id_aa64dfr0_el1,
 	  .reset = read_sanitised_id_aa64dfr0_el1,
-	  .val = ID_AA64DFR0_EL1_PMUVer_MASK, },
+	/*
+	 * Prior to FEAT_Debugv8.9, the architecture defines context-aware
+	 * breakpoints (CTX_CMPs) as the highest numbered breakpoints (BRPs).
+	 * KVM does not trap + emulate the breakpoint registers, and as such
+	 * cannot support a layout that misaligns with the underlying hardware.
+	 * While it may be possible to describe a subset that aligns with
+	 * hardware, just prevent changes to BRPs and CTX_CMPs altogether for
+	 * simplicity.
+	 *
+	 * See DDI0487K.a, section D2.8.3 Breakpoint types and linking
+	 * of breakpoints for more details.
+	 */
+	  .val = ID_AA64DFR0_EL1_DoubleLock_MASK |
+		 ID_AA64DFR0_EL1_WRPs_MASK |
+		 ID_AA64DFR0_EL1_PMUVer_MASK |
+		 ID_AA64DFR0_EL1_DebugVer_MASK, },
 	ID_SANITISED(ID_AA64DFR1_EL1),
 	ID_UNALLOCATED(5,2),
 	ID_UNALLOCATED(5,3),
@@ -2150,9 +2275,15 @@ static const struct sys_reg_desc sys_reg_descs[] = {
 	ID_UNALLOCATED(5,7),
 
 	/* CRm=6 */
-	ID_SANITISED(ID_AA64ISAR0_EL1),
-	ID_SANITISED(ID_AA64ISAR1_EL1),
-	ID_SANITISED(ID_AA64ISAR2_EL1),
+	ID_WRITABLE(ID_AA64ISAR0_EL1, ~ID_AA64ISAR0_EL1_RES0),
+	ID_WRITABLE(ID_AA64ISAR1_EL1, ~(ID_AA64ISAR1_EL1_GPI |
+					ID_AA64ISAR1_EL1_GPA |
+					ID_AA64ISAR1_EL1_API |
+					ID_AA64ISAR1_EL1_APA)),
+	ID_WRITABLE(ID_AA64ISAR2_EL1, ~(ID_AA64ISAR2_EL1_RES0 |
+					ID_AA64ISAR2_EL1_MOPS |
+					ID_AA64ISAR2_EL1_APA3 |
+					ID_AA64ISAR2_EL1_GPA3)),
 	ID_UNALLOCATED(6,3),
 	ID_UNALLOCATED(6,4),
 	ID_UNALLOCATED(6,5),
@@ -2160,9 +2291,21 @@ static const struct sys_reg_desc sys_reg_descs[] = {
 	ID_UNALLOCATED(6,7),
 
 	/* CRm=7 */
-	ID_SANITISED(ID_AA64MMFR0_EL1),
-	ID_SANITISED(ID_AA64MMFR1_EL1),
-	ID_SANITISED(ID_AA64MMFR2_EL1),
+	ID_WRITABLE(ID_AA64MMFR0_EL1, ~(ID_AA64MMFR0_EL1_RES0 |
+					ID_AA64MMFR0_EL1_TGRAN4_2 |
+					ID_AA64MMFR0_EL1_TGRAN64_2 |
+					ID_AA64MMFR0_EL1_TGRAN16_2)),
+	ID_WRITABLE(ID_AA64MMFR1_EL1, ~(ID_AA64MMFR1_EL1_RES0 |
+					ID_AA64MMFR1_EL1_TWED |
+					ID_AA64MMFR1_EL1_XNX |
+					ID_AA64MMFR1_EL1_VH |
+					ID_AA64MMFR1_EL1_VMIDBits)),
+	ID_WRITABLE(ID_AA64MMFR2_EL1, ~(ID_AA64MMFR2_EL1_RES0 |
+					ID_AA64MMFR2_EL1_EVT |
+					ID_AA64MMFR2_EL1_FWB |
+					ID_AA64MMFR2_EL1_IDS |
+					ID_AA64MMFR2_EL1_NV |
+					ID_AA64MMFR2_EL1_CCIDX)),
 	ID_SANITISED(ID_AA64MMFR3_EL1),
 	ID_UNALLOCATED(7,4),
 	ID_UNALLOCATED(7,5),
@@ -2276,11 +2419,15 @@ static const struct sys_reg_desc sys_reg_descs[] = {
 
 	{ SYS_DESC(SYS_CCSIDR_EL1), access_ccsidr },
 	{ SYS_DESC(SYS_CLIDR_EL1), access_clidr, reset_clidr, CLIDR_EL1,
-	  .set_user = set_clidr },
+	  .set_user = set_clidr, .val = ~CLIDR_EL1_RES0 },
 	{ SYS_DESC(SYS_CCSIDR2_EL1), undef_access },
 	{ SYS_DESC(SYS_SMIDR_EL1), undef_access },
 	{ SYS_DESC(SYS_CSSELR_EL1), access_csselr, reset_unknown, CSSELR_EL1 },
-	{ SYS_DESC(SYS_CTR_EL0), access_ctr },
+	ID_WRITABLE(CTR_EL0, CTR_EL0_DIC_MASK |
+					CTR_EL0_IDC_MASK |
+					CTR_EL0_DminLine_MASK |
+					CTR_EL0_L1Ip_MASK |
+					CTR_EL0_IminLine_MASK),
 	{ SYS_DESC(SYS_SVCR), undef_access },
 
 	{ PMU_SYS_REG(PMCR_EL0), .access = access_pmcr,
@@ -2555,14 +2702,15 @@ 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);
-		u32 el3 = !!cpuid_feature_extract_unsigned_field(pfr, ID_AA64PFR0_EL1_EL3_SHIFT);
-
-		p->regval = ((((dfr >> ID_AA64DFR0_EL1_WRPs_SHIFT) & 0xf) << 28) |
-			     (((dfr >> ID_AA64DFR0_EL1_BRPs_SHIFT) & 0xf) << 24) |
-			     (((dfr >> ID_AA64DFR0_EL1_CTX_CMPs_SHIFT) & 0xf) << 20)
-			     | (6 << 16) | (1 << 15) | (el3 << 14) | (el3 << 12));
+		u64 dfr = IDREG(vcpu->kvm, SYS_ID_AA64DFR0_EL1);
+		u64 pfr = IDREG(vcpu->kvm, SYS_ID_AA64PFR0_EL1);
+		u32 el3 = !!SYS_FIELD_GET(ID_AA64PFR0_EL1, EL3, pfr);
+
+		p->regval = ((SYS_FIELD_GET(ID_AA64DFR0_EL1, WRPs, dfr) << 28) |
+			     (SYS_FIELD_GET(ID_AA64DFR0_EL1, BRPs, dfr) << 24) |
+			     (SYS_FIELD_GET(ID_AA64DFR0_EL1, CTX_CMPs, dfr) << 20) |
+			     (SYS_FIELD_GET(ID_AA64DFR0_EL1, DebugVer, dfr) << 16) |
+			     (1 << 15) | (el3 << 14) | (el3 << 12));
 		return true;
 	}
 }
@@ -3394,8 +3542,8 @@ id_to_sys_reg_desc(struct kvm_vcpu *vcpu, u64 id,
  */
 
 #define FUNCTION_INVARIANT(reg)						\
-	static u64 get_##reg(struct kvm_vcpu *v,			\
-			      const struct sys_reg_desc *r)		\
+	static u64 reset_##reg(struct kvm_vcpu *v,			\
+			       const struct sys_reg_desc *r)		\
 	{								\
 		((struct sys_reg_desc *)r)->val = read_sysreg(reg);	\
 		return ((struct sys_reg_desc *)r)->val;			\
@@ -3405,18 +3553,11 @@ FUNCTION_INVARIANT(midr_el1)
 FUNCTION_INVARIANT(revidr_el1)
 FUNCTION_INVARIANT(aidr_el1)
 
-static u64 get_ctr_el0(struct kvm_vcpu *v, const struct sys_reg_desc *r)
-{
-	((struct sys_reg_desc *)r)->val = read_sanitised_ftr_reg(SYS_CTR_EL0);
-	return ((struct sys_reg_desc *)r)->val;
-}
-
 /* ->val is filled in by kvm_sys_reg_table_init() */
 static struct sys_reg_desc invariant_sys_regs[] __ro_after_init = {
-	{ SYS_DESC(SYS_MIDR_EL1), NULL, get_midr_el1 },
-	{ SYS_DESC(SYS_REVIDR_EL1), NULL, get_revidr_el1 },
-	{ SYS_DESC(SYS_AIDR_EL1), NULL, get_aidr_el1 },
-	{ SYS_DESC(SYS_CTR_EL0), NULL, get_ctr_el0 },
+	{ SYS_DESC(SYS_MIDR_EL1), NULL, reset_midr_el1 },
+	{ SYS_DESC(SYS_REVIDR_EL1), NULL, reset_revidr_el1 },
+	{ SYS_DESC(SYS_AIDR_EL1), NULL, reset_aidr_el1 },
 };
 
 static int get_invariant_sys_reg(u64 id, u64 __user *uaddr)
@@ -3698,6 +3839,56 @@ int kvm_arm_copy_sys_reg_indices(struct kvm_vcpu *vcpu, u64 __user *uindices)
 	return write_demux_regids(uindices);
 }
 
+#define KVM_ARM_FEATURE_ID_RANGE_INDEX(r)			\
+	KVM_ARM_FEATURE_ID_RANGE_IDX(sys_reg_Op0(r),		\
+		sys_reg_Op1(r),					\
+		sys_reg_CRn(r),					\
+		sys_reg_CRm(r),					\
+		sys_reg_Op2(r))
+
+static bool is_feature_id_reg(u32 encoding)
+{
+	return (sys_reg_Op0(encoding) == 3 &&
+		(sys_reg_Op1(encoding) < 2 || sys_reg_Op1(encoding) == 3) &&
+		sys_reg_CRn(encoding) == 0 &&
+		sys_reg_CRm(encoding) <= 7);
+}
+
+int kvm_vm_ioctl_get_reg_writable_masks(struct kvm *kvm, struct reg_mask_range *range)
+{
+	const void *zero_page = page_to_virt(ZERO_PAGE(0));
+	u64 __user *masks = (u64 __user *)range->addr;
+
+	/* Only feature id range is supported, reserved[13] must be zero. */
+	if (range->range ||
+	    memcmp(range->reserved, zero_page, sizeof(range->reserved)))
+		return -EINVAL;
+
+	/* Wipe the whole thing first */
+	if (clear_user(masks, KVM_ARM_FEATURE_ID_RANGE_SIZE * sizeof(__u64)))
+		return -EFAULT;
+
+	for (int i = 0; i < ARRAY_SIZE(sys_reg_descs); i++) {
+		const struct sys_reg_desc *reg = &sys_reg_descs[i];
+		u32 encoding = reg_to_encoding(reg);
+		u64 val;
+
+		if (!is_feature_id_reg(encoding) || !reg->set_user)
+			continue;
+
+		if (!reg->val ||
+		    (is_aa32_id_reg(encoding) && !kvm_supports_32bit_el0())) {
+			continue;
+		}
+		val = reg->val;
+
+		if (put_user(val, (masks + KVM_ARM_FEATURE_ID_RANGE_INDEX(encoding))))
+			return -EFAULT;
+	}
+
+	return 0;
+}
+
 int __init kvm_sys_reg_table_init(void)
 {
 	struct sys_reg_params params;
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index f97ab651ccbb7aa89d9127fcde026c4f375803f4..cab3566ea863a2110a0dfcda0f3d0ad29d0b7ffd 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1201,6 +1201,8 @@ struct kvm_ppc_resize_hpt {
 #define KVM_CAP_ARM_EAGER_SPLIT_CHUNK_SIZE 228
 #define KVM_CAP_ARM_SUPPORTED_BLOCK_SIZES 229
 
+#define KVM_CAP_ARM_SUPPORTED_REG_MASK_RANGES 231
+
 #define KVM_CAP_SEV_ES_GHCB 500
 #define KVM_CAP_HYGON_COCO_EXT 501
 /* support userspace to request firmware to build CSV3 guest's memory space */
@@ -1625,6 +1627,7 @@ struct kvm_s390_ucas_mapping {
 #define KVM_ARM_MTE_COPY_TAGS	  _IOR(KVMIO,  0xb4, struct kvm_arm_copy_mte_tags)
 /* Available with KVM_CAP_COUNTER_OFFSET */
 #define KVM_ARM_SET_COUNTER_OFFSET _IOW(KVMIO,  0xb5, struct kvm_arm_counter_offset)
+#define KVM_ARM_GET_REG_WRITABLE_MASKS _IOR(KVMIO,  0xb6, struct reg_mask_range)
 
 /* ioctl for SW vcpu init*/
 #define KVM_SW64_VCPU_INIT	  _IO(KVMIO,  0xba)