diff options
| author | Jing Zhang <jingzhangos@google.com> | 2023-10-03 23:03:58 +0000 |
|---|---|---|
| committer | Oliver Upton <oliver.upton@linux.dev> | 2023-10-04 17:10:15 +0000 |
| commit | 6656cda0f3b269cb87cfb5773d3369e6d96e83db (patch) | |
| tree | c45c1d25f6d533903f2e6c73d7b223c884095c8c /Documentation/virt | |
| parent | 3f9cd0ca848413fd368278310d2cdd6c2bef48b2 (diff) | |
KVM: arm64: Document KVM_ARM_GET_REG_WRITABLE_MASKS
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>
Diffstat (limited to 'Documentation/virt')
| -rw-r--r-- | Documentation/virt/kvm/api.rst | 48 |
1 files changed, 48 insertions, 0 deletions
diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst index 21a7578142a1..c4cb703e37d1 100644 --- a/Documentation/virt/kvm/api.rst +++ b/Documentation/virt/kvm/api.rst @@ -6070,6 +6070,54 @@ 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 ======================== |