linux-kernel - Re: [RFC PATCH 26/39] KVM: guest_memfd: Track faultability within a struct kvm_gmem

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Message-ID: <ZxFhTtEs2Mz7Dj-O@x1n>
Date: Thu, 17 Oct 2024 15:11:10 -0400
From: Peter Xu <peterx@...hat.com>
To: Jason Gunthorpe <jgg@...dia.com>
Cc: David Hildenbrand <david@...hat.com>,
	Ackerley Tng <ackerleytng@...gle.com>, tabba@...gle.com,
	quic_eberman@...cinc.com, roypat@...zon.co.uk, rientjes@...gle.com,
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	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	kvm@...r.kernel.org, linux-kselftest@...r.kernel.org
Subject: Re: [RFC PATCH 26/39] KVM: guest_memfd: Track faultability within a
 struct kvm_gmem_private

On Thu, Oct 17, 2024 at 02:10:10PM -0300, Jason Gunthorpe wrote:
> > If so, maybe that's a non-issue for non-CoCo, where the VM object /
> > gmemfd object (when created) can have a flag marking that it's
> > always shared and can never be converted to private for any page
> > within.
> 
> What is non-CoCo? Does it include the private/shared concept?

I used that to represent the possible gmemfd use cases outside confidential
computing.

So the private/shared things should still be around as fundamental property
of gmemfd, but it should be always shared and no convertion needed for the
whole lifecycle of the gmemfd when marked !CoCo.

Basically, that's the KVM-only hugetlbfs v2.. especially if this series
will move on with hugetlb allocators, that's even closer.. which makes some
sense to me at least for now to avoid reinvent the wheels all over the
places over cgroup/pool/meminfo/etc.

-- 
Peter Xu