linux-kernel - Re: [PATCH] x86/mce: Make machine check speculation protected

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Date:   Thu, 18 Jan 2018 16:46:07 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
        Borislav Petkov <bp@...en8.de>,
        David Woodhouse <dwmw@...zon.co.uk>
Subject: Re: [PATCH] x86/mce: Make machine check speculation protected

On Thu, Jan 18, 2018 at 04:28:26PM +0100, Thomas Gleixner wrote:
> The machine check idtentry uses an indirect branch directly from the low
> level code. This evades the speculation protection.
> 
> Replace it by a direct call into C code and issue the indirect call there
> so the compiler can apply the proper speculation protection.
> 
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> ---
>  arch/x86/entry/entry_64.S        |    2 +-
>  arch/x86/include/asm/traps.h     |    1 +
>  arch/x86/kernel/cpu/mcheck/mce.c |    5 +++++
>  3 files changed, 7 insertions(+), 1 deletion(-)
> 
> --- a/arch/x86/entry/entry_64.S
> +++ b/arch/x86/entry/entry_64.S
> @@ -1264,7 +1264,7 @@ idtentry async_page_fault	do_async_page_
>  #endif
>  
>  #ifdef CONFIG_X86_MCE
> -idtentry machine_check					has_error_code=0	paranoid=1 do_sym=*machine_check_vector(%rip)
> +idtentry machine_check		do_mce			has_error_code=0	paranoid=1

Nice, Thanks!