Re: [PATCH v5 2/7] KVM: guest_memfd: Rename invalidate() arch hook to reclaim() and isolate it

[Ackerley Tng]

Sean Christopherson <seanjc@xxxxxxxxxx> writes:

> Rename guest_memfd's invalidate() hook to reclaim() and isolate it via its
> own RECLAIM Kconfig, as the hook is called when a folio is freed, which is
> far too late and lacks sufficient information for KVM to actually
> invalidate its usage of the memory.  E.g. SNP uses the hook to convert
> memory back to SHARED so that it can be safely accessed by the host, there
> is no invalidation of guest mappings anywhere.  Isolating the hook will
> also allow pKVM on arm64 to opt-in to reclaim() without also having to
> differentiate between reclaim and conversions to shared for active VMs.
>
> Keep guest_memfd's trampoline, even though it would be trivial to wire up
> .free_folio() directly to an arch callback, to avoid bleeding guest_memfd
> internals into arch code (specifically, avoid referencing folios in arch
> code).
>
> Leave the kvm_x86_ops hook as-is for the moment, as the hook can be dropped
> entirely ("reclaim" on SNP is the same as convert-to-shared).
>
>
> [...snip...]
>

Reviewed-by: Ackerley Tng <ackerleytng@xxxxxxxxxx>