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Sender: Paolo Bonzini <paolo.bonzini@gmail.com>
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Date:   Tue, 8 Mar 2022 13:17:02 +0100
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Subject: Re: [PATCH v4 01/12] mm/shmem: Introduce F_SEAL_INACCESSIBLE
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To:     Chao Peng <chao.p.peng@linux.intel.com>,
        Andy Lutomirski <luto@kernel.org>
Cc:     Steven Price <steven.price@arm.com>,
        kvm list <kvm@vger.kernel.org>,
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        Jonathan Corbet <corbet@lwn.net>,
        Sean Christopherson <seanjc@google.com>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        Jim Mattson <jmattson@google.com>,
        Joerg Roedel <joro@8bytes.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        the arch/x86 maintainers <x86@kernel.org>,
        "H. Peter Anvin" <hpa@zytor.com>, Hugh Dickins <hughd@google.com>,
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        "J . Bruce Fields" <bfields@fieldses.org>,
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        Yu Zhang <yu.c.zhang@linux.intel.com>,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        "Nakajima, Jun" <jun.nakajima@intel.com>,
        Dave Hansen <dave.hansen@intel.com>,
        Andi Kleen <ak@linux.intel.com>,
        David Hildenbrand <david@redhat.com>
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From:   Paolo Bonzini <pbonzini@redhat.com>
In-Reply-To: <20220307132602.GA58690@chaop.bj.intel.com>
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On 3/7/22 14:26, Chao Peng wrote:
>> In pseudo-Rust, this is the difference between:
>>
>> fn convert_to_private(in: &mut Memfd)
>>
>> and
>>
>> fn convert_to_private(in: Memfd) -> PrivateMemoryFd
>>
>> This doesn't map particularly nicely to the kernel, though.
> I understand this Rust semantics and the difficulty to handle races.
> Probably we should not expose F_SEAL_INACCESSIBLE to userspace, instead
> we can use a new in-kernel flag to indicate the same thing. That flag
> should be set only when the memfd is created with MFD_INACCESSIBLE.

Yes, I like this.

Paolo