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Date:   Tue, 8 Mar 2022 09:45:45 +0800
From:   Chao Peng <chao.p.peng@linux.intel.com>
To:     Vlastimil Babka <vbabka@suse.cz>
Cc:     kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org, linux-fsdevel@vger.kernel.org,
        qemu-devel@nongnu.org, Paolo Bonzini <pbonzini@redhat.com>,
        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>,
        x86@kernel.org, "H . Peter Anvin" <hpa@zytor.com>,
        Hugh Dickins <hughd@google.com>,
        Jeff Layton <jlayton@kernel.org>,
        "J . Bruce Fields" <bfields@fieldses.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Yu Zhang <yu.c.zhang@linux.intel.com>,
        "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
        luto@kernel.org, jun.nakajima@intel.com, dave.hansen@intel.com,
        ak@linux.intel.com, david@redhat.com
Subject: Re: [PATCH v4 03/12] mm: Introduce memfile_notifier
Message-ID: <20220308014545.GA43625@chaop.bj.intel.com>
Reply-To: Chao Peng <chao.p.peng@linux.intel.com>
References: <20220118132121.31388-1-chao.p.peng@linux.intel.com>
 <20220118132121.31388-4-chao.p.peng@linux.intel.com>
 <9ac9a88f-54b4-a49f-0857-c3094d3e0d2b@suse.cz>
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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@linux.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