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Date:   Fri, 27 Aug 2021 11:24:13 -0700
From:   "Andy Lutomirski" <luto@kernel.org>
To:     "David Hildenbrand" <david@redhat.com>,
        "Sean Christopherson" <seanjc@google.com>,
        "Paolo Bonzini" <pbonzini@redhat.com>
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        "Wanpeng Li" <wanpengli@tencent.com>,
        "Jim Mattson" <jmattson@google.com>,
        "Joerg Roedel" <joro@8bytes.org>, "kvm list" <kvm@vger.kernel.org>,
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Subject: =?UTF-8?Q?Re:_[RFC]_KVM:_mm:_fd-based_approach_for_supporting_KVM_guest_?=
 =?UTF-8?Q?private_memory?=
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On Thu, Aug 26, 2021, at 2:26 PM, David Hildenbrand wrote:
> On 26.08.21 19:05, Andy Lutomirski wrote:

> > Oof.  That's quite a requirement.  What's the point of the VMA once all
> > this is done?
> 
> You can keep using things like mbind(), madvise(), ... and the GUP code 
> with a special flag might mostly just do what you want. You won't have 
> to reinvent too many wheels on the page fault logic side at least.
> 

You can keep calling the functions.  The implementations working is a different story: you can't just unmap (pte_numa-style or otherwise) a private guest page to quiesce it, move it with memcpy(), and then fault it back in.

In any event, adding fd-based NUMA APIs would be quite nice.  Look at the numactl command.