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Date:   Fri, 9 Feb 2018 20:11:12 +0100
From:   Joerg Roedel <jroedel@suse.de>
To:     Andy Lutomirski <luto@kernel.org>
Cc:     Joerg Roedel <joro@8bytes.org>,
        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>,
        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>,
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        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>,
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        Kees Cook <keescook@google.com>,
        Andrea Arcangeli <aarcange@redhat.com>,
        Waiman Long <llong@redhat.com>, Pavel Machek <pavel@ucw.cz>
Subject: Re: [PATCH 00/31 v2] PTI support for x86_32
Message-ID: <20180209191112.55zyjf4njum75brd@suse.de>
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Hi Andy,

On Fri, Feb 09, 2018 at 05:47:43PM +0000, Andy Lutomirski wrote:
> 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."

Thanks for your review. I can add this warning, but I just hope that not
a lot of people will actually see it :)


	Joerg