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author | Marc Zyngier <maz@kernel.org> | 2023-04-21 11:43:38 +0300 |
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committer | Marc Zyngier <maz@kernel.org> | 2023-04-21 11:44:32 +0300 |
commit | 6dcf7316e05eccded11fc640813c8a8879f271a6 (patch) | |
tree | 57b3585f2c317e4e201ab12630062ab272025e4e /Documentation/virt/kvm | |
parent | 367eb095b841a1af8a4a1425021ac43159049dcd (diff) | |
parent | c5284f6d8ce2b9cf96643da441862434233a4ea3 (diff) | |
download | linux-6dcf7316e05eccded11fc640813c8a8879f271a6.tar.xz |
Merge branch kvm-arm64/smccc-filtering into kvmarm-master/next
* kvm-arm64/smccc-filtering:
: .
: SMCCC call filtering and forwarding to userspace, courtesy of
: Oliver Upton. From the cover letter:
:
: "The Arm SMCCC is rather prescriptive in regards to the allocation of
: SMCCC function ID ranges. Many of the hypercall ranges have an
: associated specification from Arm (FF-A, PSCI, SDEI, etc.) with some
: room for vendor-specific implementations.
:
: The ever-expanding SMCCC surface leaves a lot of work within KVM for
: providing new features. Furthermore, KVM implements its own
: vendor-specific ABI, with little room for other implementations (like
: Hyper-V, for example). Rather than cramming it all into the kernel we
: should provide a way for userspace to handle hypercalls."
: .
KVM: selftests: Fix spelling mistake "KVM_HYPERCAL_EXIT_SMC" -> "KVM_HYPERCALL_EXIT_SMC"
KVM: arm64: Test that SMC64 arch calls are reserved
KVM: arm64: Prevent userspace from handling SMC64 arch range
KVM: arm64: Expose SMC/HVC width to userspace
KVM: selftests: Add test for SMCCC filter
KVM: selftests: Add a helper for SMCCC calls with SMC instruction
KVM: arm64: Let errors from SMCCC emulation to reach userspace
KVM: arm64: Return NOT_SUPPORTED to guest for unknown PSCI version
KVM: arm64: Introduce support for userspace SMCCC filtering
KVM: arm64: Add support for KVM_EXIT_HYPERCALL
KVM: arm64: Use a maple tree to represent the SMCCC filter
KVM: arm64: Refactor hvc filtering to support different actions
KVM: arm64: Start handling SMCs from EL1
KVM: arm64: Rename SMC/HVC call handler to reflect reality
KVM: arm64: Add vm fd device attribute accessors
KVM: arm64: Add a helper to check if a VM has ran once
KVM: x86: Redefine 'longmode' as a flag for KVM_EXIT_HYPERCALL
Signed-off-by: Marc Zyngier <maz@kernel.org>
Diffstat (limited to 'Documentation/virt/kvm')
-rw-r--r-- | Documentation/virt/kvm/api.rst | 33 | ||||
-rw-r--r-- | Documentation/virt/kvm/devices/vm.rst | 79 |
2 files changed, 108 insertions, 4 deletions
diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst index 192adcb61add..42403dfe9496 100644 --- a/Documentation/virt/kvm/api.rst +++ b/Documentation/virt/kvm/api.rst @@ -6256,15 +6256,40 @@ to the byte array. __u64 nr; __u64 args[6]; __u64 ret; - __u32 longmode; - __u32 pad; + __u64 flags; } hypercall; -Unused. This was once used for 'hypercall to userspace'. To implement -such functionality, use KVM_EXIT_IO (x86) or KVM_EXIT_MMIO (all except s390). + +It is strongly recommended that userspace use ``KVM_EXIT_IO`` (x86) or +``KVM_EXIT_MMIO`` (all except s390) to implement functionality that +requires a guest to interact with host userpace. .. note:: KVM_EXIT_IO is significantly faster than KVM_EXIT_MMIO. +For arm64: +---------- + +SMCCC exits can be enabled depending on the configuration of the SMCCC +filter. See the Documentation/virt/kvm/devices/vm.rst +``KVM_ARM_SMCCC_FILTER`` for more details. + +``nr`` contains the function ID of the guest's SMCCC call. Userspace is +expected to use the ``KVM_GET_ONE_REG`` ioctl to retrieve the call +parameters from the vCPU's GPRs. + +Definition of ``flags``: + - ``KVM_HYPERCALL_EXIT_SMC``: Indicates that the guest used the SMC + conduit to initiate the SMCCC call. If this bit is 0 then the guest + used the HVC conduit for the SMCCC call. + + - ``KVM_HYPERCALL_EXIT_16BIT``: Indicates that the guest used a 16bit + instruction to initiate the SMCCC call. If this bit is 0 then the + guest used a 32bit instruction. An AArch64 guest always has this + bit set to 0. + +At the point of exit, PC points to the instruction immediately following +the trapping instruction. + :: /* KVM_EXIT_TPR_ACCESS */ diff --git a/Documentation/virt/kvm/devices/vm.rst b/Documentation/virt/kvm/devices/vm.rst index 147efec626e5..9d726e60ec47 100644 --- a/Documentation/virt/kvm/devices/vm.rst +++ b/Documentation/virt/kvm/devices/vm.rst @@ -321,3 +321,82 @@ Allows userspace to query the status of migration mode. if it is enabled :Returns: -EFAULT if the given address is not accessible from kernel space; 0 in case of success. + +6. GROUP: KVM_ARM_VM_SMCCC_CTRL +=============================== + +:Architectures: arm64 + +6.1. ATTRIBUTE: KVM_ARM_VM_SMCCC_FILTER (w/o) +--------------------------------------------- + +:Parameters: Pointer to a ``struct kvm_smccc_filter`` + +:Returns: + + ====== =========================================== + EEXIST Range intersects with a previously inserted + or reserved range + EBUSY A vCPU in the VM has already run + EINVAL Invalid filter configuration + ENOMEM Failed to allocate memory for the in-kernel + representation of the SMCCC filter + ====== =========================================== + +Requests the installation of an SMCCC call filter described as follows:: + + enum kvm_smccc_filter_action { + KVM_SMCCC_FILTER_HANDLE = 0, + KVM_SMCCC_FILTER_DENY, + KVM_SMCCC_FILTER_FWD_TO_USER, + }; + + struct kvm_smccc_filter { + __u32 base; + __u32 nr_functions; + __u8 action; + __u8 pad[15]; + }; + +The filter is defined as a set of non-overlapping ranges. Each +range defines an action to be applied to SMCCC calls within the range. +Userspace can insert multiple ranges into the filter by using +successive calls to this attribute. + +The default configuration of KVM is such that all implemented SMCCC +calls are allowed. Thus, the SMCCC filter can be defined sparsely +by userspace, only describing ranges that modify the default behavior. + +The range expressed by ``struct kvm_smccc_filter`` is +[``base``, ``base + nr_functions``). The range is not allowed to wrap, +i.e. userspace cannot rely on ``base + nr_functions`` overflowing. + +The SMCCC filter applies to both SMC and HVC calls initiated by the +guest. The SMCCC filter gates the in-kernel emulation of SMCCC calls +and as such takes effect before other interfaces that interact with +SMCCC calls (e.g. hypercall bitmap registers). + +Actions: + + - ``KVM_SMCCC_FILTER_HANDLE``: Allows the guest SMCCC call to be + handled in-kernel. It is strongly recommended that userspace *not* + explicitly describe the allowed SMCCC call ranges. + + - ``KVM_SMCCC_FILTER_DENY``: Rejects the guest SMCCC call in-kernel + and returns to the guest. + + - ``KVM_SMCCC_FILTER_FWD_TO_USER``: The guest SMCCC call is forwarded + to userspace with an exit reason of ``KVM_EXIT_HYPERCALL``. + +The ``pad`` field is reserved for future use and must be zero. KVM may +return ``-EINVAL`` if the field is nonzero. + +KVM reserves the 'Arm Architecture Calls' range of function IDs and +will reject attempts to define a filter for any portion of these ranges: + + =========== =============== + Start End (inclusive) + =========== =============== + 0x8000_0000 0x8000_FFFF + 0xC000_0000 0xC000_FFFF + =========== =============== |