| .. 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) 0xC6000002 |
| Arguments: none |
| 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) 0xC6000003 |
| 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) 0xC6000004 |
| 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) 0xC6000005 |
| 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) |
| ============== ======== ====================================== |
