From: Steven Price <steven.price@arm.com>
To: Catalin Marinas <catalin.marinas@arm.com>,
Marc Zyngier <maz@kernel.org>, Will Deacon <will@kernel.org>
Cc: Steven Price <steven.price@arm.com>,
James Morse <james.morse@arm.com>,
Julien Thierry <julien.thierry.kdev@gmail.com>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
kvmarm@lists.cs.columbia.edu,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, Dave Martin <Dave.Martin@arm.com>,
Mark Rutland <mark.rutland@arm.com>,
Thomas Gleixner <tglx@linutronix.de>,
qemu-devel@nongnu.org, Juan Quintela <quintela@redhat.com>,
"Dr. David Alan Gilbert" <dgilbert@redhat.com>,
Richard Henderson <richard.henderson@linaro.org>,
Peter Maydell <peter.maydell@linaro.org>,
Andrew Jones <drjones@redhat.com>
Subject: [PATCH v17 6/6] KVM: arm64: Document MTE capability and ioctl
Date: Mon, 21 Jun 2021 12:17:16 +0100 [thread overview]
Message-ID: <20210621111716.37157-7-steven.price@arm.com> (raw)
In-Reply-To: <20210621111716.37157-1-steven.price@arm.com>
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.
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Steven Price <steven.price@arm.com>
---
Documentation/virt/kvm/api.rst | 61 ++++++++++++++++++++++++++++++++++
1 file changed, 61 insertions(+)
diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index 7fcb2fd38f42..97661a97943f 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -5034,6 +5034,43 @@ see KVM_XEN_VCPU_SET_ATTR above.
The KVM_XEN_VCPU_ATTR_TYPE_RUNSTATE_ADJUST type may not be used
with the KVM_XEN_VCPU_GET_ATTR ioctl.
+4.130 KVM_ARM_MTE_COPY_TAGS
+---------------------------
+
+:Capability: KVM_CAP_ARM_MTE
+:Architectures: arm64
+:Type: vm ioctl
+:Parameters: struct kvm_arm_copy_mte_tags
+:Returns: number of bytes copied, < 0 on error (-EINVAL for incorrect
+ arguments, -EFAULT if memory cannot be accessed).
+
+::
+
+ struct kvm_arm_copy_mte_tags {
+ __u64 guest_ipa;
+ __u64 length;
+ void __user *addr;
+ __u64 flags;
+ __u64 reserved[2];
+ };
+
+Copies Memory Tagging Extension (MTE) tags to/from guest tag memory. The
+``guest_ipa`` and ``length`` fields must be ``PAGE_SIZE`` aligned. The ``addr``
+field must point to a buffer which the tags will be copied to or from.
+
+``flags`` specifies the direction of copy, either ``KVM_ARM_TAGS_TO_GUEST`` or
+``KVM_ARM_TAGS_FROM_GUEST``.
+
+The size of the buffer to store the tags is ``(length / 16)`` bytes
+(granules in MTE are 16 bytes long). Each byte contains a single tag
+value. This matches the format of ``PTRACE_PEEKMTETAGS`` and
+``PTRACE_POKEMTETAGS``.
+
+If an error occurs before any data is copied then a negative error code is
+returned. If some tags have been copied before an error occurs then the number
+of bytes successfully copied is returned. If the call completes successfully
+then ``length`` is returned.
+
5. The kvm_run structure
========================
@@ -6362,6 +6399,30 @@ default.
See Documentation/x86/sgx/2.Kernel-internals.rst for more details.
+7.26 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 creating any VCPUs to allow the guest access. Note that MTE is only
+available to a guest running in AArch64 mode and enabling this capability will
+cause attempts to create AArch32 VCPUs to fail.
+
+When enabled the guest is able to access tags associated with any memory given
+to the guest. KVM will ensure 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 this capability is enabled all memory in memslots must be mapped as
+not-shareable (no MAP_SHARED), attempts to create a memslot with a
+MAP_SHARED mmap will result in an -EINVAL return.
+
+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.
======================
--
2.20.1
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next prev parent reply other threads:[~2021-06-21 11:21 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-21 11:17 [PATCH v17 0/6] MTE support for KVM guest Steven Price
2021-06-21 11:17 ` [PATCH v17 1/6] arm64: mte: Sync tags for pages where PTE is untagged Steven Price
2021-06-21 11:17 ` [PATCH v17 2/6] KVM: arm64: Introduce MTE VM feature Steven Price
2021-06-21 17:00 ` Fuad Tabba
2021-06-22 11:29 ` Marc Zyngier
2021-06-21 11:17 ` [PATCH v17 3/6] KVM: arm64: Save/restore MTE registers Steven Price
2021-06-22 9:46 ` Fuad Tabba
2021-06-21 11:17 ` [PATCH v17 4/6] KVM: arm64: Expose KVM_ARM_CAP_MTE Steven Price
2021-06-22 8:07 ` Fuad Tabba
2021-06-22 8:48 ` Marc Zyngier
2021-06-21 11:17 ` [PATCH v17 5/6] KVM: arm64: ioctl to fetch/store tags in a guest Steven Price
2021-06-22 8:56 ` Fuad Tabba
2021-06-22 10:25 ` Marc Zyngier
2021-06-22 10:56 ` Fuad Tabba
2021-06-23 14:07 ` Steven Price
2021-06-24 13:35 ` Marc Zyngier
2021-06-24 13:42 ` Steven Price
2021-06-21 11:17 ` Steven Price [this message]
2021-06-22 9:42 ` [PATCH v17 6/6] KVM: arm64: Document MTE capability and ioctl Fuad Tabba
2021-06-22 10:35 ` Marc Zyngier
2021-06-22 10:41 ` Fuad Tabba
2021-06-22 14:21 ` [PATCH v17 0/6] MTE support for KVM guest Marc Zyngier
2021-06-23 14:09 ` Steven Price
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