Merge branch kvm-arm64/writable-id-regs into kvmarm/next

* kvm-arm64/writable-id-regs:
  : Writable ID registers, courtesy of Jing Zhang
  :
  : This series significantly expands the architectural feature set that
  : userspace can manipulate via the ID registers. A new ioctl is defined
  : that makes the mutable fields in the ID registers discoverable to
  : userspace.
  KVM: selftests: Avoid using forced target for generating arm64 headers
  tools headers arm64: Fix references to top srcdir in Makefile
  KVM: arm64: selftests: Test for setting ID register from usersapce
  tools headers arm64: Update sysreg.h with kernel sources
  KVM: selftests: Generate sysreg-defs.h and add to include path
  perf build: Generate arm64's sysreg-defs.h and add to include path
  tools: arm64: Add a Makefile for generating sysreg-defs.h
  KVM: arm64: Document vCPU feature selection UAPIs
  KVM: arm64: Allow userspace to change ID_AA64ZFR0_EL1
  KVM: arm64: Allow userspace to change ID_AA64PFR0_EL1
  KVM: arm64: Allow userspace to change ID_AA64MMFR{0-2}_EL1
  KVM: arm64: Allow userspace to change ID_AA64ISAR{0-2}_EL1
  KVM: arm64: Bump up the default KVM sanitised debug version to v8p8
  KVM: arm64: Reject attempts to set invalid debug arch version
  KVM: arm64: Advertise selected DebugVer in DBGDIDR.Version
  KVM: arm64: Use guest ID register values for the sake of emulation
  KVM: arm64: Document KVM_ARM_GET_REG_WRITABLE_MASKS
  KVM: arm64: Allow userspace to get the writable masks for feature ID registers

Signed-off-by: Oliver Upton <oliver.upton@linux.dev>

2 files changed, 34 insertions, 0 deletions

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 6a0b6f3b6f41..846a7706e925 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -1108,6 +1108,8 @@ 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);
diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h
index f7ddd73a8c0f..89d2fc872d9f 100644
--- a/arch/arm64/include/uapi/asm/kvm.h
+++ b/arch/arm64/include/uapi/asm/kvm.h
@@ -505,6 +505,38 @@ 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__ */