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From:   Andy Lutomirski <luto@kernel.org>
Date:   Fri, 9 Feb 2018 17:47:43 +0000
Message-ID: <CALCETrUF61fqjXKG=kwf83JWpw=kgL16UvKowezDVwVA1=YVAw@mail.gmail.com>
Subject: Re: [PATCH 00/31 v2] PTI support for x86_32
To:     Joerg Roedel <joro@8bytes.org>
Cc:     Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@kernel.org>,
        "H . Peter Anvin" <hpa@zytor.com>, X86 ML <x86@kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Linux-MM <linux-mm@kvack.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Andy Lutomirski <luto@kernel.org>,
        Dave Hansen <dave.hansen@intel.com>,
        Josh Poimboeuf <jpoimboe@redhat.com>,
        Juergen Gross <jgross@suse.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Borislav Petkov <bp@alien8.de>, Jiri Kosina <jkosina@suse.cz>,
        Boris Ostrovsky <boris.ostrovsky@oracle.com>,
        Brian Gerst <brgerst@gmail.com>,
        David Laight <David.Laight@aculab.com>,
        Denys Vlasenko <dvlasenk@redhat.com>,
        Eduardo Valentin <eduval@amazon.com>,
        Greg KH <gregkh@linuxfoundation.org>,
        Will Deacon <will.deacon@arm.com>,
        "Liguori, Anthony" <aliguori@amazon.com>,
        Daniel Gruss <daniel.gruss@iaik.tugraz.at>,
        Hugh Dickins <hughd@google.com>,
        Kees Cook <keescook@google.com>,
        Andrea Arcangeli <aarcange@redhat.com>,
        Waiman Long <llong@redhat.com>, Pavel Machek <pavel@ucw.cz>,
        Joerg Roedel <jroedel@suse.de>
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On Fri, Feb 9, 2018 at 9:25 AM, Joerg Roedel <joro@8bytes.org> wrote:
> Hi,
>
> here is the second version of my PTI implementation for
> x86_32, based on tip/x86-pti-for-linus. It took a lot longer
> than I had hoped, but there have been a number of obstacles
> on the way. It also isn't the small patch-set anymore that v1
> was, but compared to it this one actually works :)

One thing worth noting is that performance of this whole series is
going to be abysmal due to the complete lack of 32-bit PCID.  Maybe
any kernel built with this option set that runs on a CPU that has the
PCID bit set in CPUID should print a big fat warning like "WARNING:
you are using 32-bit PTI on a 64-bit PCID-capable CPU.  Your
performance will increase dramatically if you switch to a 64-bit
kernel."