7eed5740ff
Firstly, the hypercall IDs have been renumbered but that was not reflected in the documentation. Secondly, the argument registers r1-r3 are checked to be zero when calling ARM_SMCCC_KVM_FUNC_MMIO_GUARD_INFO. Signed-off-by: Keir Fraser <keirf@google.com> Bug: 265943840 Change-Id: I9684d1e71af7d8627d079cfd89d437cfc28be09f
75 lines
3.3 KiB
ReStructuredText
75 lines
3.3 KiB
ReStructuredText
.. 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)
|
|
============== ======== ======================================
|