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| author | Oliver Upton <oliver.upton@linux.dev> | 2023-04-04 15:40:45 +0000 |
|---|---|---|
| committer | Marc Zyngier <maz@kernel.org> | 2023-04-05 12:07:41 +0100 |
| commit | d824dff1919bbd523d4d5c860437d043c0ad121d (patch) | |
| tree | 0ea664fd97f3afdb2edd9bb787b7d79161530535 /Documentation/virt | |
| parent | fb88707dd39bd1d5ec4a058776de9ee99bcc7b72 (diff) | |
| download | linux-d824dff1919bbd523d4d5c860437d043c0ad121d.tar.gz | |
KVM: arm64: Add support for KVM_EXIT_HYPERCALL
In anticipation of user hypercall filters, add the necessary plumbing to
get SMCCC calls out to userspace. Even though the exit structure has
space for KVM to pass register arguments, let's just avoid it altogether
and let userspace poke at the registers via KVM_GET_ONE_REG.
This deliberately stretches the definition of a 'hypercall' to cover
SMCs from EL1 in addition to the HVCs we know and love. KVM doesn't
support EL1 calls into secure services, but now we can paint that as a
userspace problem and be done with it.
Finally, we need a flag to let userspace know what conduit instruction
was used (i.e. SMC vs. HVC).
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20230404154050.2270077-9-oliver.upton@linux.dev
Diffstat (limited to 'Documentation/virt')
| -rw-r--r-- | Documentation/virt/kvm/api.rst | 18 |
1 files changed, 16 insertions, 2 deletions
diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst index 9b01e3d0e7577b..9497792c4ee566 100644 --- a/Documentation/virt/kvm/api.rst +++ b/Documentation/virt/kvm/api.rst @@ -6221,11 +6221,25 @@ to the byte array. __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: +---------- + +``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_EXIT_TPR_ACCESS */ |