From: Jing Zhang <jingzhangos@google.com> mainline inclusion from mainline-v6.7-rc1 commit 6656cda0f3b269cb87cfb5773d3369e6d96e83db category: feature bugzilla: https://gitee.com/openeuler/kernel/issues/IBN3WI CVE: NA Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... ---------------------------------------------------------------------- Add some basic documentation on how to get feature ID register writable masks from userspace. Signed-off-by: Jing Zhang <jingzhangos@google.com> Reviewed-by: Cornelia Huck <cohuck@redhat.com> Reviewed-by: Marc Zyngier <maz@kernel.org> Link: https://lore.kernel.org/r/20231003230408.3405722-3-oliver.upton@linux.dev Signed-off-by: Oliver Upton <oliver.upton@linux.dev> --- Documentation/virt/kvm/api.rst | 48 ++++++++++++++++++++++++++++++++++ 1 file changed, 48 insertions(+) diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst index c40b6a09ffd8..a379d779cbee 100644 --- a/Documentation/virt/kvm/api.rst +++ b/Documentation/virt/kvm/api.rst @@ -6148,6 +6148,54 @@ 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. +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 ======================== -- 2.33.0