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

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Message-ID: <20241016225157.GQ3559746@nvidia.com>
Date: Wed, 16 Oct 2024 19:51:57 -0300
From: Jason Gunthorpe <jgg@...dia.com>
To: Peter Xu <peterx@...hat.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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	pgonda@...gle.com, oliver.upton@...ux.dev,
	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 Wed, Oct 16, 2024 at 04:16:17PM -0400, Peter Xu wrote:
> 
> Is there chance that when !CoCo will be supported, then external modules
> (e.g. VFIO) can reuse the old user mappings, just like before gmemfd?
> 
> To support CoCo, I understand gmem+offset is required all over the places.
> However in a non-CoCo context, I wonder whether the other modules are
> required to stick with gmem+offset, or they can reuse the old VA ways,
> because how it works can fundamentally be the same as before, except that
> the folios now will be managed by gmemfd.

My intention with iommufd was to see fd + offest as the "new" way
to refer to all guest memory and discourage people from using VMA
handles.

Jason