linux-kernel - Re: [PATCH v7 00/14] KVM: mm: fd-based approach for supporting KVM guest private memory

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Message-ID: <20220902123010.zfyv6apmo3v67a2i@box.shutemov.name>
Date:   Fri, 2 Sep 2022 15:30:10 +0300
From:   "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>
To:     Chao Peng <chao.p.peng@...ux.intel.com>
Cc:     Hugh Dickins <hughd@...gle.com>,
        "Kirill A. Shutemov" <kirill@...temov.name>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linux-fsdevel@...r.kernel.org, linux-api@...r.kernel.org,
        linux-doc@...r.kernel.org, qemu-devel@...gnu.org,
        linux-kselftest@...r.kernel.org,
        Paolo Bonzini <pbonzini@...hat.com>,
        Jonathan Corbet <corbet@....net>,
        Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        x86@...nel.org, "H . Peter Anvin" <hpa@...or.com>,
        Jeff Layton <jlayton@...nel.org>,
        "J . Bruce Fields" <bfields@...ldses.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Shuah Khan <shuah@...nel.org>, Mike Rapoport <rppt@...nel.org>,
        Steven Price <steven.price@....com>,
        "Maciej S . Szmigiero" <mail@...iej.szmigiero.name>,
        Vlastimil Babka <vbabka@...e.cz>,
        Vishal Annapurve <vannapurve@...gle.com>,
        Yu Zhang <yu.c.zhang@...ux.intel.com>, luto@...nel.org,
        jun.nakajima@...el.com, dave.hansen@...el.com, ak@...ux.intel.com,
        david@...hat.com, aarcange@...hat.com, ddutile@...hat.com,
        dhildenb@...hat.com, Quentin Perret <qperret@...gle.com>,
        Michael Roth <michael.roth@....com>, mhocko@...e.com,
        Muchun Song <songmuchun@...edance.com>,
        "Gupta, Pankaj" <pankaj.gupta@....com>,
        Elena Reshetova <elena.reshetova@...el.com>
Subject: Re: [PATCH v7 00/14] KVM: mm: fd-based approach for supporting KVM
 guest private memory

On Fri, Sep 02, 2022 at 06:27:57PM +0800, Chao Peng wrote:
> > +	if (flags & MFD_INACCESSIBLE) {
> > +		struct file *inaccessible_file;
> > +
> > +		inaccessible_file = memfd_mkinaccessible(file);
> > +		if (IS_ERR(inaccessible_file)) {
> > +			error = PTR_ERR(inaccessible_file);
> > +			goto err_file;
> > +		}
> 
> The new file should alse be marked as O_LARGEFILE otherwise setting the
> initial size greater than 2^31 on the fd will be refused by ftruncate().
> 
> +               inaccessible_file->f_flags |= O_LARGEFILE;
> +

Good catch. Thanks.

I will modify memfd_mkinaccessible() to do this.

-- 
  Kiryl Shutsemau / Kirill A. Shutemov