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From: Hugh Dickins <hughd@google.com>
To: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Hugh Dickins <hughd@google.com>,
	"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
	Chao Peng <chao.p.peng@linux.intel.com>,
	kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-mm@kvack.org, linux-fsdevel@vger.kernel.org,
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	Sean Christopherson <seanjc@google.com>,
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	Wanpeng Li <wanpengli@tencent.com>,
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	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
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	ak@linux.intel.com, david@redhat.com, aarcange@redhat.com,
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	Quentin Perret <qperret@google.com>,
	Michael Roth <michael.roth@amd.com>,
	mhocko@suse.com, Muchun Song <songmuchun@bytedance.com>,
	"Gupta, Pankaj" <pankaj.gupta@amd.com>
Subject: Re: [PATCH v7 00/14] KVM: mm: fd-based approach for supporting KVM guest private memory
Date: Sat, 20 Aug 2022 22:15:32 -0700 (PDT)	[thread overview]
Message-ID: <c194262b-b634-4baf-abf0-dc727e8f1d7@google.com> (raw)
In-Reply-To: <20220820002700.6yflrxklmpsavdzi@box.shutemov.name>

On Sat, 20 Aug 2022, Kirill A. Shutemov wrote:
> 
> Yes, INACCESSIBLE is increase of complexity which you do not want to deal
> with in shmem.c. It get it.

It's not so much that INACCESSIBLE increases the complexity of
memfd/shmem/tmpfs, as that it is completely foreign to it.

And by handling all those foreign needs at the KVM end (where you
can be sure that the mem attached to the fd is INACCESSIBLE because
you have given nobody access to it - no handshaking with 3rd party
required).

> 
> I will try next week to rework it as shim to top of shmem. Does it work
> for you?

Yes, please do, thanks.  It's a compromise between us: the initial TDX
case has no justification to use shmem at all, but doing it that way
will help you with some of the infrastructure, and will probably be
easiest for KVM to extend to other more relaxed fd cases later.

> 
> But I think it is wrong to throw it over the fence to KVM folks and say it
> is your problem. Core MM has to manage it.

We disagree on who is throwing over the fence to whom :)

Core MM should manage the core MM parts and KVM should manage the KVM
parts.  What makes this rather different from most driver usage of MM,
is that KVM seems likely to use a great proportion of memory this way.
With great memory usage comes great responsibility: I don't think
all those flags and seals and notifiers let KVM escape from that.

Hugh

  reply	other threads:[~2022-08-21  5:16 UTC|newest]

Thread overview: 172+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-07-06  8:20 [PATCH v7 00/14] KVM: mm: fd-based approach for supporting KVM guest private memory Chao Peng
2022-07-06  8:20 ` [PATCH v7 01/14] mm: Add F_SEAL_AUTO_ALLOCATE seal to memfd Chao Peng
2022-07-21  9:44   ` David Hildenbrand
2022-07-21  9:50     ` David Hildenbrand
2022-07-21 15:05       ` Sean Christopherson
2022-07-25 13:46         ` Chao Peng
2022-07-21 10:27     ` Gupta, Pankaj
2022-07-25 13:54       ` Chao Peng
2022-07-25 14:49         ` Gupta, Pankaj
2022-07-25 13:42     ` Chao Peng
2022-08-05 17:55     ` Paolo Bonzini
2022-08-05 18:06       ` David Hildenbrand
2022-08-10  9:40         ` Chao Peng
2022-08-10  9:38       ` Chao Peng
2022-08-17 23:41       ` Kirill A. Shutemov
2022-08-18  9:09         ` Paolo Bonzini
2022-08-23  7:36         ` David Hildenbrand
2022-08-24 10:20           ` Chao Peng
2022-08-26 15:19   ` Fuad Tabba
2022-08-29 15:18     ` Chao Peng
2022-07-06  8:20 ` [PATCH v7 02/14] selftests/memfd: Add tests for F_SEAL_AUTO_ALLOCATE Chao Peng
2022-08-05 13:11   ` David Hildenbrand
2022-07-06  8:20 ` [PATCH v7 03/14] mm: Introduce memfile_notifier Chao Peng
2022-08-05 13:22   ` David Hildenbrand
2022-08-10  9:22     ` Chao Peng
2022-08-10 10:05       ` David Hildenbrand
2022-08-10 14:38         ` Sean Christopherson
2022-08-11 12:27           ` Quentin Perret
2022-08-11 13:39             ` Chao Peng
2022-07-06  8:20 ` [PATCH v7 04/14] mm/shmem: Support memfile_notifier Chao Peng
2022-07-12 18:02   ` Gupta, Pankaj
2022-07-13  7:44     ` Chao Peng
2022-07-13 10:01       ` Gupta, Pankaj
2022-07-13 23:49         ` Chao Peng
2022-07-14  4:15           ` Gupta, Pankaj
2022-08-05 13:26   ` David Hildenbrand
2022-08-10  9:25     ` Chao Peng
2022-07-06  8:20 ` [PATCH v7 05/14] mm/memfd: Introduce MFD_INACCESSIBLE flag Chao Peng
2022-08-05 13:28   ` David Hildenbrand
2022-08-10  9:37     ` Chao Peng
2022-08-10  9:55       ` David Hildenbrand
2022-08-11 13:17         ` Chao Peng
2022-09-07 16:18     ` Kirill A. Shutemov
2022-07-06  8:20 ` [PATCH v7 06/14] KVM: Rename KVM_PRIVATE_MEM_SLOTS to KVM_INTERNAL_MEM_SLOTS Chao Peng
2022-07-06  8:20 ` [PATCH v7 07/14] KVM: Use gfn instead of hva for mmu_notifier_retry Chao Peng
2022-07-15 11:36   ` Gupta, Pankaj
2022-07-18 13:29     ` Chao Peng
2022-07-18 15:26       ` Sean Christopherson
2022-07-19 14:02         ` Chao Peng
2022-08-04  7:10   ` Isaku Yamahata
2022-08-10  8:19     ` Chao Peng
2022-07-06  8:20 ` [PATCH v7 08/14] KVM: Rename mmu_notifier_* Chao Peng
2022-07-29 19:02   ` Sean Christopherson
2022-08-03 10:13     ` Chao Peng
2022-08-05 19:54     ` Paolo Bonzini
2022-08-10  8:09       ` Chao Peng
2023-05-23  7:19   ` Kautuk Consul
2023-05-23 14:19     ` Sean Christopherson
2023-05-24  6:12       ` Kautuk Consul
2023-05-24 20:16         ` Sean Christopherson
2023-05-24 20:33           ` Peter Zijlstra
2023-05-24 21:39             ` Sean Christopherson
2023-05-25  8:54               ` Peter Zijlstra
2023-05-25  3:52             ` Kautuk Consul
2023-05-24 20:28         ` Peter Zijlstra
2022-07-06  8:20 ` [PATCH v7 09/14] KVM: Extend the memslot to support fd-based private memory Chao Peng
2022-07-29 19:51   ` Sean Christopherson
2022-08-03 10:08     ` Chao Peng
2022-08-03 14:42       ` Sean Christopherson
2022-07-06  8:20 ` [PATCH v7 10/14] KVM: Add KVM_EXIT_MEMORY_FAULT exit Chao Peng
2022-07-06  8:20 ` [PATCH v7 11/14] KVM: Register/unregister the guest private memory regions Chao Peng
2022-07-19  8:00   ` Gupta, Pankaj
2022-07-19 14:08     ` Chao Peng
2022-07-19 14:23       ` Gupta, Pankaj
2022-07-20 15:07         ` Chao Peng
2022-07-20 15:31           ` Gupta, Pankaj
2022-07-20 16:21             ` Sean Christopherson
2022-07-20 17:41               ` Gupta, Pankaj
2022-07-21  7:34               ` Wei Wang
2022-07-21  9:29                 ` Chao Peng
2022-07-21 17:58                   ` Sean Christopherson
2022-07-25 13:04                     ` Chao Peng
2022-07-29 19:54                       ` Sean Christopherson
2022-08-02  0:49                         ` Sean Christopherson
2022-08-02 16:38                           ` Sean Christopherson
2022-08-03  9:48                             ` Chao Peng
2022-08-03 15:51                               ` Sean Christopherson
2022-08-04  7:58                                 ` Chao Peng
2022-07-20 16:44   ` Sean Christopherson
2022-07-21  9:37     ` Chao Peng
2022-08-19 19:37   ` Vishal Annapurve
2022-08-24 10:37     ` Chao Peng
2022-08-26 15:19   ` Fuad Tabba
2022-08-29 15:21     ` Chao Peng
2022-07-06  8:20 ` [PATCH v7 12/14] KVM: Handle page fault for private memory Chao Peng
2022-07-29 20:58   ` Sean Christopherson
2022-08-03  9:52     ` Chao Peng
2022-07-06  8:20 ` [PATCH v7 13/14] KVM: Enable and expose KVM_MEM_PRIVATE Chao Peng
2022-07-19  9:55   ` Gupta, Pankaj
2022-07-19 14:12     ` Chao Peng
2022-07-06  8:20 ` [PATCH v7 14/14] memfd_create.2: Describe MFD_INACCESSIBLE flag Chao Peng
2022-08-01 14:40   ` Dave Hansen
2022-08-03  9:53     ` Chao Peng
2022-07-13  3:58 ` [PATCH v7 00/14] KVM: mm: fd-based approach for supporting KVM guest private memory Gupta, Pankaj
2022-07-13  7:57   ` Chao Peng
2022-07-13 10:35     ` Gupta, Pankaj
2022-07-13 23:59       ` Chao Peng
2022-07-14  4:39         ` Gupta, Pankaj
2022-07-14  5:06           ` Gupta, Pankaj
2022-07-14  4:29       ` Andy Lutomirski
2022-07-14  5:13         ` Gupta, Pankaj
2022-08-11 10:02 ` Nikunj A. Dadhania
2022-08-11 11:30   ` Gupta, Pankaj
2022-08-11 13:32     ` Chao Peng
2022-08-11 17:28       ` Nikunj A. Dadhania
2022-08-12  3:22       ` Nikunj A. Dadhania
2022-08-11 17:18     ` Nikunj A. Dadhania
2022-08-11 23:02       ` Gupta, Pankaj
2022-08-12  6:02         ` Gupta, Pankaj
2022-08-12  7:18           ` Gupta, Pankaj
2022-08-12  8:48             ` Nikunj A. Dadhania
2022-08-12  9:33               ` Gupta, Pankaj
2022-08-15 13:04               ` Chao Peng
2022-08-16  4:28                 ` Nikunj A. Dadhania
2022-08-16 11:33                 ` Gupta, Pankaj
2022-08-16 12:24                   ` Kirill A . Shutemov
2022-08-16 13:03                     ` Gupta, Pankaj
2022-08-16 15:38                       ` Sean Christopherson
2022-08-17 15:27                         ` Michael Roth
2022-08-23  1:25                           ` Isaku Yamahata
2022-08-23 17:41                         ` Gupta, Pankaj
2022-08-18  5:40 ` Hugh Dickins
2022-08-18 13:24   ` Kirill A . Shutemov
2022-08-19  0:20     ` Sean Christopherson
2022-08-19  3:38       ` Hugh Dickins
2022-08-19 22:53         ` Sean Christopherson
2022-08-23  7:55         ` David Hildenbrand
2022-08-23 16:05           ` Sean Christopherson
2022-08-24  9:41             ` Chao Peng
2022-09-09  4:55               ` Andy Lutomirski
2022-08-19  3:00     ` Hugh Dickins
2022-08-20  0:27       ` Kirill A. Shutemov
2022-08-21  5:15         ` Hugh Dickins [this message]
2022-08-31 14:24           ` Kirill A . Shutemov
2022-09-02 10:27             ` Chao Peng
2022-09-02 12:30               ` Kirill A . Shutemov
2022-09-08  1:10             ` Kirill A. Shutemov
2022-09-13  9:44               ` Sean Christopherson
2022-09-13 13:28                 ` Kirill A. Shutemov
2022-09-13 14:53                   ` Sean Christopherson
2022-09-13 16:00                     ` Kirill A. Shutemov
2022-09-13 16:12                       ` Sean Christopherson
2022-09-09  4:48         ` Andy Lutomirski
2022-09-09 14:32           ` Kirill A . Shutemov
2022-09-09 19:11             ` Andy Lutomirski
2022-09-09 23:02               ` Kirill A . Shutemov
2022-08-21 10:27       ` Matthew Wilcox
2022-08-24 10:27         ` Chao Peng
2022-09-09  4:44     ` Andy Lutomirski
     [not found]     ` <diqzlej60z57.fsf@ackerleytng-cloudtop.c.googlers.com>
     [not found]       ` <20221202061347.1070246-2-chao.p.peng@linux.intel.com>
2023-04-13 15:25         ` Christian Brauner
2023-04-13 22:28           ` Sean Christopherson
2023-04-14 22:38             ` Ackerley Tng
2023-04-14 23:26               ` Sean Christopherson
2023-04-15  0:06                 ` Sean Christopherson
2023-04-19  8:29             ` Christian Brauner
2023-04-20  0:49               ` Sean Christopherson
2023-04-20  8:35                 ` Christian Brauner
2022-08-26 15:19 ` Fuad Tabba
2022-08-29 15:17   ` Chao Peng
2022-08-31  9:12     ` Fuad Tabba
2022-09-02 10:19       ` Chao Peng
2022-09-09 15:35 ` Michael Roth

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