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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Fri, 23 Mar 2018 17:54:35 -0700
Message-ID: <CA+55aFxZ2-3pOpBRPZ4SmDrhQGQY-+AigsqxWXfXzvv-KDeM8Q@mail.gmail.com>
Subject: Re: [PATCH 00/11] Use global pages with PTI
To:     Dave Hansen <dave.hansen@linux.intel.com>
Cc:     Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        linux-mm <linux-mm@kvack.org>,
        Andrea Arcangeli <aarcange@redhat.com>,
        Andrew Lutomirski <luto@kernel.org>,
        Kees Cook <keescook@google.com>,
        Hugh Dickins <hughd@google.com>,
        =?UTF-8?B?SsO8cmdlbiBHcm/Dnw==?= <jgross@suse.com>,
        "the arch/x86 maintainers" <x86@kernel.org>, namit@vmware.com
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On Fri, Mar 23, 2018 at 5:46 PM, Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>
> It is, of course, possible that I misunderstood what you actually
> benchmarked. But I assume the above benchmark numbers are with the
> whole "don't even do global entries if you have PCID".

Oh, I went back and read your description, and realized that I _had_
misunderstood what you did.

I thought you didn't bother with global pages at all when you had PCID.

But that's not what you meant. You always do global for the actual
user-mapped kernel pages, but when you don't have PCID you do *all*
kernel test as global, whether shared or not.

So I entirely misread what the latest change was.

                     Linus