[PATCH v9 6/6] KVM: arm64: Document MTE capability and ioctl
From: Steven Price <steven.price@arm.com>
Date: 2021-03-01 14:27:14
Also in:
kvmarm, lkml, qemu-devel
Subsystem:
documentation, kernel virtual machine (kvm), the rest · Maintainers:
Jonathan Corbet, Paolo Bonzini, Linus Torvalds
A new capability (KVM_CAP_ARM_MTE) identifies that the kernel supports granting a guest access to the tags, and provides a mechanism for the VMM to enable it. A new ioctl (KVM_ARM_MTE_COPY_TAGS) provides a simple way for a VMM to access the tags of a guest without having to maintain a PROT_MTE mapping in userspace. The above capability gates access to the ioctl. Signed-off-by: Steven Price <steven.price@arm.com> --- Documentation/virt/kvm/api.rst | 37 ++++++++++++++++++++++++++++++++++ 1 file changed, 37 insertions(+)
diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index aed52b0fc16e..1406ea138127 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst@@ -4939,6 +4939,23 @@ KVM_XEN_VCPU_ATTR_TYPE_VCPU_TIME_INFO Allows Xen vCPU attributes to be read. For the structure and types, see KVM_XEN_VCPU_SET_ATTR above. +4.131 KVM_ARM_MTE_COPY_TAGS +--------------------------- + +:Capability: KVM_CAP_ARM_MTE +:Architectures: arm64 +:Type: vm ioctl +:Parameters: struct kvm_arm_copy_mte_tags +:Returns: 0 on success, < 0 on error + +Copies Memory Tagging Extension (MTE) tags to/from guest tag memory. The +starting address and length of guest memory must be ``PAGE_SIZE`` aligned. + +The size of the buffer to store the tags is ``(length / MTE_GRANULE_SIZE)`` +bytes (i.e. 1/16th of the corresponding size). Each byte contains a single tag +value. This matches the format of ``PTRACE_PEEKMTETAGS`` and +``PTRACE_POKEMTETAGS``. + 5. The kvm_run structure ========================
@@ -6227,6 +6244,25 @@ KVM_RUN_BUS_LOCK flag is used to distinguish between them. This capability can be used to check / enable 2nd DAWR feature provided by POWER10 processor. +7.23 KVM_CAP_ARM_MTE +-------------------- + +:Architectures: arm64 +:Parameters: none + +This capability indicates that KVM (and the hardware) supports exposing the +Memory Tagging Extensions (MTE) to the guest. It must also be enabled by the +VMM before the guest will be granted access. + +When enabled the guest is able to access tags associated with any memory given +to the guest. KVM will ensure that the pages are flagged ``PG_mte_tagged`` so +that the tags are maintained during swap or hibernation of the host, however +the VMM needs to manually save/restore the tags as appropriate if the VM is +migrated. + +When enabled the VMM may make use of the ``KVM_ARM_MTE_COPY_TAGS`` ioctl to +perform a bulk copy of tags to/from the guest + 8. Other capabilities. ======================
@@ -6716,3 +6752,4 @@ KVM_XEN_HVM_SET_ATTR, KVM_XEN_HVM_GET_ATTR, KVM_XEN_VCPU_SET_ATTR and KVM_XEN_VCPU_GET_ATTR ioctls, as well as the delivery of exception vectors for event channel upcalls when the evtchn_upcall_pending field of a vcpu's vcpu_info is set. +
--
2.20.1
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