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From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Thu, 11 Jan 2018 11:09:13 -0800
Message-ID: <CA+55aFxji41K_MdLAKiZ7MaXNT4w=OV0yQiTvroJs0_jy6DUOw@mail.gmail.com>
Subject: Re: [PATCH 4.4 00/37] 4.4.110-stable review
To: Pavel Tatashin <pasha.tatashin@oracle.com>,
        Thomas Gleixner <tglx@linutronix.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Andy Lutomirski <luto@kernel.org>,
        Hugh Dickins <hughd@google.com>, Thomas Voegtle <tv@lio96.de>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Guenter Roeck <linux@roeck-us.net>,
        Shuah Khan <shuahkh@osg.samsung.com>, patches@kernelci.org,
        Ben Hutchings <ben.hutchings@codethink.co.uk>,
        lkft-triage@lists.linaro.org, stable <stable@vger.kernel.org>,
        Steve Sistare <steven.sistare@oracle.com>
Content-Type: text/plain; charset="UTF-8"
Sender: linux-kernel-owner@vger.kernel.org

[ Patch to make sure the EFI trampoline_pgd is properly aligned and
has the double pgd that KPTI requires ]

On Thu, Jan 11, 2018 at 10:40 AM, Pavel Tatashin
<pasha.tatashin@oracle.com> wrote:
> If it is better to resubmit this patch via git send-email, please let me know.

It would be better, because that way the patch can be more easily
quoted and discussed.

That said, I do not see why this isn't an issue upstream too.

As far as I can tell, it's not just 4.4.110. Our current entry code
does that ADJUST_KERNEL_CR3 dance too, which clears the
PTI_SWITCH_MASK bit from cr3.

And that realmode trampoline pgd seems all to be just aligned to PAGE_SIZE.

Now, in the modern world, we generate new page tables for EFI, but we
still have that EFI_OLD_MEMMAP code that disables that. And afaik,
EFI_OLD_MEMMAP has the exact same problem that your patch fixes in 4.4
(where it's always on).

So I think this patch should go into the development kernel too.

Or maybe it already is, and I just haven't gotten it yet.

Or - even more likely - I'm missing something entirely, and even
EFI_OLD_MEMMAP solved this some other way upstream.

Adding Thomas Gleixner explicitly to the participants so that he can
tell me I'm a moron and point me to the right thing.

               Linus