75 lines
3.2 KiB
ReStructuredText
75 lines
3.2 KiB
ReStructuredText
.. SPDX-License-Identifier: GPL-2.0
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==============
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KVM MMIO guard
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==============
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KVM implements device emulation by handling translation faults to any
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IPA range that is not contained in a memory slot. Such a translation
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fault is in most cases passed on to userspace (or in rare cases to the
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host kernel) with the address, size and possibly data of the access
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for emulation.
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Should the guest exit with an address that is not one that corresponds
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to an emulatable device, userspace may take measures that are not the
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most graceful as far as the guest is concerned (such as terminating it
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or delivering a fatal exception).
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There is also an element of trust: by forwarding the request to
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userspace, the kernel assumes that the guest trusts userspace to do
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the right thing.
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The KVM MMIO guard offers a way to mitigate this last point: a guest
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can request that only certain regions of the IPA space are valid as
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MMIO. Only these regions will be handled as an MMIO, and any other
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will result in an exception being delivered to the guest.
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This relies on a set of hypercalls defined in the KVM-specific range,
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using the HVC64 calling convention.
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* ARM_SMCCC_KVM_FUNC_MMIO_GUARD_INFO
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============== ======== ================================
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Function ID: (uint32) 0xC6000002
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Arguments: none
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Return Values: (int64) NOT_SUPPORTED(-1) on error, or
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(uint64) Protection Granule (PG) size in
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bytes (r0)
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============== ======== ================================
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* ARM_SMCCC_KVM_FUNC_MMIO_GUARD_ENROLL
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============== ======== ==============================
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Function ID: (uint32) 0xC6000003
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Arguments: none
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Return Values: (int64) NOT_SUPPORTED(-1) on error, or
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RET_SUCCESS(0) (r0)
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============== ======== ==============================
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* ARM_SMCCC_KVM_FUNC_MMIO_GUARD_MAP
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============== ======== ====================================
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Function ID: (uint32) 0xC6000004
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Arguments: (uint64) The base of the PG-sized IPA range
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that is allowed to be accessed as
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MMIO. Must be aligned to the PG size
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(r1)
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(uint64) Index in the MAIR_EL1 register
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providing the memory attribute that
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is used by the guest (r2)
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Return Values: (int64) NOT_SUPPORTED(-1) on error, or
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RET_SUCCESS(0) (r0)
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============== ======== ====================================
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* ARM_SMCCC_KVM_FUNC_MMIO_GUARD_UNMAP
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============== ======== ======================================
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Function ID: (uint32) 0xC6000005
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Arguments: (uint64) PG-sized IPA range aligned to the PG
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size which has been previously mapped.
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Must be aligned to the PG size and
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have been previously mapped (r1)
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Return Values: (int64) NOT_SUPPORTED(-1) on error, or
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RET_SUCCESS(0) (r0)
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============== ======== ======================================
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