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From:   Jim Mattson <jmattson@google.com>
Date:   Fri, 9 Feb 2018 14:55:47 -0800
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Subject: Re: [RFC 03/12] KVM/VMX: Use the new host mapping API for virtual_apic_page
To:     KarimAllah Ahmed <karahmed@amazon.com>
Cc:     KarimAllah Ahmed <karahmed@amazon.de>,
        LKML <linux-kernel@vger.kernel.org>,
        kvm list <kvm@vger.kernel.org>,
        Paolo Bonzini <pbonzini@redhat.com>,
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On Fri, Feb 9, 2018 at 4:15 AM, KarimAllah Ahmed <karahmed@amazon.com> wrote:

> Can you elaborate a bit? I do not really understand what is the concern.

I can't find the posting that gave me this impression. The only thing
I can find is the following in Documentation/vm/highmem.txt:

 (*) kmap().  This permits a short duration mapping of a single page.  It needs
     global synchronization, but is amortized somewhat.  It is also prone to
     deadlocks when using in a nested fashion, and so it is not recommended for
     new code.

What constitutes a "short duration," and does this new usage qualify?