linux-kernel - Re: [PATCH 4/4] x86/asm: Change sync_core() to use MOV to CR2 to serialize

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Message-ID: <20161201092228.calajwwv4k4k4l6f@pd.tnic>
Date:   Thu, 1 Dec 2016 10:22:28 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Andy Lutomirski <luto@...nel.org>
Cc:     x86@...nel.org, One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Brian Gerst <brgerst@...il.com>,
        Matthew Whitehead <tedheadster@...il.com>,
        Henrique de Moraes Holschuh <hmh@....eng.br>
Subject: Re: [PATCH 4/4] x86/asm: Change sync_core() to use MOV to CR2 to
 serialize

On Wed, Nov 30, 2016 at 12:34:55PM -0800, Andy Lutomirski wrote:
> Aside from being excessively slow, CPUID is problematic: Linux runs
> on a handful of CPUs that don't have CPUID.  MOV to CR2 is always
> available, so use it instead.
> 
> Signed-off-by: Andy Lutomirski <luto@...nel.org>
> ---
>  arch/x86/include/asm/processor.h | 31 ++++++++-----------------------
>  1 file changed, 8 insertions(+), 23 deletions(-)

Looks nice.

I'm wondering if we should leave this one in tip for an additional cycle
to have it tested on more hw. I know, it is architectural and so on but
who knows what every implementation actually does...

-- 
Regards/Gruss,
    Boris.

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