linux-kernel - Re: [PATCH v4 03/12] mm: Introduce memfile

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Date:   Tue, 8 Mar 2022 09:45:45 +0800
From:   Chao Peng <chao.p.peng@...ux.intel.com>
To:     Vlastimil Babka <vbabka@...e.cz>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, linux-fsdevel@...r.kernel.org,
        qemu-devel@...gnu.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>,
        Hugh Dickins <hughd@...gle.com>,
        Jeff Layton <jlayton@...nel.org>,
        "J . Bruce Fields" <bfields@...ldses.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Yu Zhang <yu.c.zhang@...ux.intel.com>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        luto@...nel.org, jun.nakajima@...el.com, dave.hansen@...el.com,
        ak@...ux.intel.com, david@...hat.com
Subject: Re: [PATCH v4 03/12] mm: Introduce memfile_notifier

On Mon, Mar 07, 2022 at 04:42:08PM +0100, Vlastimil Babka wrote:
> On 1/18/22 14:21, Chao Peng wrote:
> > This patch introduces memfile_notifier facility so existing memory file
> > subsystems (e.g. tmpfs/hugetlbfs) can provide memory pages to allow a
> > third kernel component to make use of memory bookmarked in the memory
> > file and gets notified when the pages in the memory file become
> > allocated/invalidated.
> > 
> > It will be used for KVM to use a file descriptor as the guest memory
> > backing store and KVM will use this memfile_notifier interface to
> > interact with memory file subsystems. In the future there might be other
> > consumers (e.g. VFIO with encrypted device memory).
> > 
> > It consists two sets of callbacks:
> >   - memfile_notifier_ops: callbacks for memory backing store to notify
> >     KVM when memory gets allocated/invalidated.
> >   - memfile_pfn_ops: callbacks for KVM to call into memory backing store
> >     to request memory pages for guest private memory.
> > 
> > Userspace is in charge of guest memory lifecycle: it first allocates
> > pages in memory backing store and then passes the fd to KVM and lets KVM
> > register each memory slot to memory backing store via
> > memfile_register_notifier.
> > 
> > The supported memory backing store should maintain a memfile_notifier list
> > and provide routine for memfile_notifier to get the list head address and
> > memfile_pfn_ops callbacks for memfile_register_notifier. It also should call
> > memfile_notifier_fallocate/memfile_notifier_invalidate when the bookmarked
> > memory gets allocated/invalidated.
> > 
> > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> 
> Process nitpick:
> Here and in patch 4/12 you have Kirill's S-o-b so there should probably be
> also "From: Kirill ..." as was in v3? Or in case you modified the original
> patches so much to become the primary author, you should add
> "Co-developed-by: Kirill ..." here before his S-o-b.

Thanks. 3/12 is vastly rewritten so the latter case can be applied.
4/12 should keep Kirill as the primary author.

Chao