Hi David,
On 11/03/2024 16:20, David Matlack wrote:
On Sun, Mar 10, 2024 at 9:46 PM Oliver Upton <oliver.upton@xxxxxxxxx> wrote:
2. What is your best guess as to when KVM userfault patches will be available,
even if only in RFC form?
We're aiming for the end of April for RFC with KVM/ARM support.
Just to make sure everyone is read in on what this entails -- is this
the implementation that only worries about vCPUs touching non-present
memory, leaving the question of other UAPIs that consume guest memory
(e.g. GIC/ITS table save/restore) up for further discussion?
Yes. The initial version will only support returning to userspace on
invalid vCPU accesses with KVM_EXIT_MEMORY_FAULT. Non-vCPU accesses to
invalid pages (e.g. GIC/ITS table save/restore) will trigger an error
return from __gfn_to_hva_many() (which will cause the corresponding
ioctl to fail). It will be userspace's responsibility to clear the
invalid attribute before invoking those ioctls.
For x86 we may need an blocking kernel-to-userspace notification
mechanism for code paths in the emulator, but we'd like to investigate
and discuss if there are any other cleaner alternatives before going
too far down that route.
I wasn't able to locate any follow-ups on the LKML about this topic.
May I know if you are still working on or planning to work on this?
Thanks,
Nikita
