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- .. SPDX-License-Identifier: GPL-2.0
- ==============
- KVM MMIO guard
- ==============
- KVM implements device emulation by handling translation faults to any
- IPA range that is not contained in a memory slot. Such a translation
- fault is in most cases passed on to userspace (or in rare cases to the
- host kernel) with the address, size and possibly data of the access
- for emulation.
- Should the guest exit with an address that is not one that corresponds
- to an emulatable device, userspace may take measures that are not the
- most graceful as far as the guest is concerned (such as terminating it
- or delivering a fatal exception).
- There is also an element of trust: by forwarding the request to
- userspace, the kernel assumes that the guest trusts userspace to do
- the right thing.
- The KVM MMIO guard offers a way to mitigate this last point: a guest
- can request that only certain regions of the IPA space are valid as
- MMIO. Only these regions will be handled as an MMIO, and any other
- will result in an exception being delivered to the guest.
- This relies on a set of hypercalls defined in the KVM-specific range,
- using the HVC64 calling convention.
- * ARM_SMCCC_KVM_FUNC_MMIO_GUARD_INFO
- ============== ======== ================================
- Function ID: (uint32) 0xC6000005
- Arguments: r1-r3 Reserved / Must be zero
- Return Values: (int64) NOT_SUPPORTED(-1) on error, or
- (uint64) Protection Granule (PG) size in
- bytes (r0)
- ============== ======== ================================
- * ARM_SMCCC_KVM_FUNC_MMIO_GUARD_ENROLL
- ============== ======== ==============================
- Function ID: (uint32) 0xC6000006
- Arguments: none
- Return Values: (int64) NOT_SUPPORTED(-1) on error, or
- RET_SUCCESS(0) (r0)
- ============== ======== ==============================
- * ARM_SMCCC_KVM_FUNC_MMIO_GUARD_MAP
- ============== ======== ====================================
- Function ID: (uint32) 0xC6000007
- Arguments: (uint64) The base of the PG-sized IPA range
- that is allowed to be accessed as
- MMIO. Must be aligned to the PG size
- (r1)
- (uint64) Index in the MAIR_EL1 register
- providing the memory attribute that
- is used by the guest (r2)
- Return Values: (int64) NOT_SUPPORTED(-1) on error, or
- RET_SUCCESS(0) (r0)
- ============== ======== ====================================
- * ARM_SMCCC_KVM_FUNC_MMIO_GUARD_UNMAP
- ============== ======== ======================================
- Function ID: (uint32) 0xC6000008
- Arguments: (uint64) PG-sized IPA range aligned to the PG
- size which has been previously mapped.
- Must be aligned to the PG size and
- have been previously mapped (r1)
- Return Values: (int64) NOT_SUPPORTED(-1) on error, or
- RET_SUCCESS(0) (r0)
- ============== ======== ======================================
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