linux-kernel - Re: [PATCH 1/2] x86/microcode/intel: Save microcode patch unconditionally

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Date:   Fri, 20 Apr 2018 12:54:08 +0200
From:   Vitezslav Samel <vitezslav@...el.cz>
To:     Borislav Petkov <bp@...e.de>
Cc:     "Raj, Ashok" <ashok.raj@...el.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org, x86-ml <x86@...nel.org>
Subject: Re: [PATCH 1/2] x86/microcode/intel: Save microcode patch
 unconditionally

On Fri, Apr 20, 2018 at 12:34:28PM +0200, Borislav Petkov wrote:
> save_mc_for_early() was a no-op on !CONFIG_HOTPLUG_CPU but the
> generic_load_microcode() path saves the microcode patches it has found
> into our cache of patches which is used for late loading too. Regardless
> of whether we do CPU hotplug or not.
> 
> So make the saving unconditional so that late loading can find the
> proper patch.
> 
> Reported-by: Vitezslav Samel <vitezslav@...el.cz>

  Tested-by: Vitezslav Samel <vitezslav@...el.cz>

> Signed-off-by: Borislav Petkov <bp@...e.de>
> Cc: Ashok Raj <ashok.raj@...el.com>
> Cc: <stable@...r.kernel.org> # if it has backported d8c3b52c00a05036e0a6b315b4b17921a7b67997
> Link: http://lkml.kernel.org/r/20180418081140.GA2439@pc11.op.pod.cz
> ---
>  arch/x86/kernel/cpu/microcode/intel.c | 2 --
>  1 file changed, 2 deletions(-)
> 
> diff --git a/arch/x86/kernel/cpu/microcode/intel.c b/arch/x86/kernel/cpu/microcode/intel.c
> index 32b8e5724f96..1c2cfa0644aa 100644
> --- a/arch/x86/kernel/cpu/microcode/intel.c
> +++ b/arch/x86/kernel/cpu/microcode/intel.c
> @@ -485,7 +485,6 @@ static void show_saved_mc(void)
>   */
>  static void save_mc_for_early(u8 *mc, unsigned int size)
>  {
> -#ifdef CONFIG_HOTPLUG_CPU
>  	/* Synchronization during CPU hotplug. */
>  	static DEFINE_MUTEX(x86_cpu_microcode_mutex);
>  
> @@ -495,7 +494,6 @@ static void save_mc_for_early(u8 *mc, unsigned int size)
>  	show_saved_mc();
>  
>  	mutex_unlock(&x86_cpu_microcode_mutex);
> -#endif
>  }
>  
>  static bool load_builtin_intel_microcode(struct cpio_data *cp)
> -- 
> 2.13.0
> 
> SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
> --