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Date:   Tue, 2 Jun 2020 16:33:09 +0300
From:   "Kirill A. Shutemov" <kirill@shutemov.name>
To:     Paolo Bonzini <pbonzini@redhat.com>
Cc:     Vitaly Kuznetsov <vkuznets@redhat.com>,
        David Rientjes <rientjes@google.com>,
        Andrea Arcangeli <aarcange@redhat.com>,
        Kees Cook <keescook@chromium.org>,
        Will Drewry <wad@chromium.org>,
        "Edgecombe, Rick P" <rick.p.edgecombe@intel.com>,
        "Kleen, Andi" <andi.kleen@intel.com>, x86@kernel.org,
        kvm@vger.kernel.org, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Andy Lutomirski <luto@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Sean Christopherson <sean.j.christopherson@intel.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        Jim Mattson <jmattson@google.com>,
        Joerg Roedel <joro@8bytes.org>
Subject: Re: [RFC 06/16] KVM: Use GUP instead of copy_from/to_user() to
 access guest memory
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On Mon, Jun 01, 2020 at 06:35:22PM +0200, Paolo Bonzini wrote:
> On 25/05/20 17:17, Kirill A. Shutemov wrote:
> >> Personally, I would've just added 'struct kvm' pointer to 'struct
> >> kvm_memory_slot' to be able to extract 'mem_protected' info when
> >> needed. This will make the patch much smaller.
> > Okay, can do.
> > 
> > Other thing I tried is to have per-slot flag to indicate that it's
> > protected. But Sean pointed that it's all-or-nothing feature and having
> > the flag in the slot would be misleading.
> > 
> 
> Perhaps it would be misleading, but it's an optimization.  Saving a
> pointer dereference can be worth it, also because there are some places
> where we just pass around a memslot and we don't have the struct kvm*.

Vitaly proposed to add struct kvm pointer into memslot. Do you object
against it?

-- 
 Kirill A. Shutemov