linux-kernel - Re: [PATCH RFC 0/5] mm/gup: Introduce exclusive GUP pinning

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Date: Thu, 20 Jun 2024 09:32:11 +0100
From: Fuad Tabba <tabba@...gle.com>
To: Christoph Hellwig <hch@...radead.org>
Cc: Jason Gunthorpe <jgg@...dia.com>, David Hildenbrand <david@...hat.com>, John Hubbard <jhubbard@...dia.com>, 
	Elliot Berman <quic_eberman@...cinc.com>, Andrew Morton <akpm@...ux-foundation.org>, 
	Shuah Khan <shuah@...nel.org>, Matthew Wilcox <willy@...radead.org>, maz@...nel.org, 
	kvm@...r.kernel.org, linux-arm-msm@...r.kernel.org, linux-mm@...ck.org, 
	linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org, 
	pbonzini@...hat.com
Subject: Re: [PATCH RFC 0/5] mm/gup: Introduce exclusive GUP pinning

Hi,

On Thu, Jun 20, 2024 at 5:11 AM Christoph Hellwig <hch@...radead.org> wrote:
>
> On Wed, Jun 19, 2024 at 08:51:35AM -0300, Jason Gunthorpe wrote:
> > If you can't agree with the guest_memfd people on how to get there
> > then maybe you need a guest_memfd2 for this slightly different special
> > stuff instead of intruding on the core mm so much. (though that would
> > be sad)
>
> Or we're just not going to support it at all.  It's not like supporting
> this weird usage model is a must-have for Linux to start with.

Sorry, but could you please clarify to me what usage model you're
referring to exactly, and why you think it's weird? It's just that we
have covered a few things in this thread, and to me it's not clear if
you're referring to protected VMs sharing memory, or being able to
(conditionally) map a VM's memory that's backed by guest_memfd(), or
if it's the Exclusive pin.

Thank you,
/fuad