Sender: Paolo Bonzini <paolo.bonzini@gmail.com>
Message-ID: <d54d58a4-3cd0-5fa3-3a81-b4bb27a7f511@redhat.com>
Date:   Tue, 23 Nov 2021 09:41:34 +0100
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Subject: Re: [RFC v2 PATCH 04/13] KVM: Add fd-based memslot data structure and
 utils
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To:     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, qemu-devel@nongnu.org
Cc:     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, john.ji@intel.com, susie.li@intel.com,
        jun.nakajima@intel.com, dave.hansen@intel.com, ak@linux.intel.com,
        david@redhat.com
References: <20211119134739.20218-1-chao.p.peng@linux.intel.com>
 <20211119134739.20218-5-chao.p.peng@linux.intel.com>
From:   Paolo Bonzini <pbonzini@redhat.com>
In-Reply-To: <20211119134739.20218-5-chao.p.peng@linux.intel.com>
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Precedence: bulk

On 11/19/21 14:47, Chao Peng wrote:
> For fd-based memslot store the file references for shared fd and the
> private fd (if any) in the memslot structure. Since there is no 'hva'
> concept we cannot call hva_to_pfn() to get a pfn, instead kvm_memfd_ops
> is added to get_pfn/put_pfn from the memory backing stores that provide
> these fds.
> 
> Signed-off-by: Yu Zhang<yu.c.zhang@linux.intel.com>
> Signed-off-by: Chao Peng<chao.p.peng@linux.intel.com>
> ---

What about kvm_read/write_guest?  Maybe the proposal which kept 
userspace_addr for the shared fd is more doable (it would be great to 
ultimately remove the mandatory userspace mapping for the shared fd, but 
I think KVM is not quite ready for that).

Paolo