Re: [PATCH v3 kvm/queue 11/16] KVM: Add kvm_map_gfn_range

[Chao Peng]

On Fri, Dec 24, 2021 at 12:13:51PM +0800, Chao Peng wrote:
> On Thu, Dec 23, 2021 at 06:06:19PM +0000, Sean Christopherson wrote:
> > On Thu, Dec 23, 2021, Chao Peng wrote:
> > > This new function establishes the mapping in KVM page tables for a
> > > given gfn range. It can be used in the memory fallocate callback for
> > > memfd based memory to establish the mapping for KVM secondary MMU when
> > > the pages are allocated in the memory backend.
> > 
> > NAK, under no circumstance should KVM install SPTEs in response to 
> > allocating
> > memory in a file.   The correct thing to do is to invalidate the gfn range
> > associated with the newly mapped range, i.e. wipe out any shared SPTEs 
> > associated
> > with the memslot.
> 
> Right, thanks.

BTW, I think the current fallocate() callback is just useless as long as
we don't want to install KVM SPTEs in response to allocating memory in a
file. The invalidation of the shared SPTEs should be notified through 
mmu_notifier of the shared memory backend, not memfd_notifier of the
private memory backend.

Thanks,
Chao