linux-kernel - Re: [PATCH] x86/microcode: move microcode

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Date:   Thu, 25 May 2023 17:34:26 -0700
From:   Ashok Raj <ashok_raj@...ux.intel.com>
To:     Christian Gmeiner <christian.gmeiner@...il.com>
Cc:     Borislav Petkov <bp@...en8.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org,
        Ashok Raj <ashok.raj@...el.com>
Subject: Re: [PATCH] x86/microcode: move microcode_mutex declaration

On Mon, May 22, 2023 at 08:27:12AM +0200, Christian Gmeiner wrote:
> The microcode_mutex is only used when CONFIG_MICROCODE_LATE_LOADING
> is enabled. Move it into the ifdef block.
> 
> Fixes a compiler unused-variable warning seen on gcc.
> 
> Signed-off-by: Christian Gmeiner <christian.gmeiner@...il.com>

Thanks Christian

I tried to compile with W=1 but not sure why I'm not getting that error
when CONFIG_MICROCODE_LATE_LOADING=n

I'm using GCC 12.2.0 on a ubuntu system.

But  your change seems fine.


> ---
>  arch/x86/kernel/cpu/microcode/core.c | 28 ++++++++++++++--------------
>  1 file changed, 14 insertions(+), 14 deletions(-)
> 
> diff --git a/arch/x86/kernel/cpu/microcode/core.c b/arch/x86/kernel/cpu/microcode/core.c
> index 3afcf3de0dd4..4f6ebadba2fb 100644
> --- a/arch/x86/kernel/cpu/microcode/core.c
> +++ b/arch/x86/kernel/cpu/microcode/core.c
> @@ -49,20 +49,6 @@ bool initrd_gone;
>  
>  LIST_HEAD(microcode_cache);
>  
> -/*
> - * Synchronization.
> - *
> - * All non cpu-hotplug-callback call sites use:
> - *
> - * - microcode_mutex to synchronize with each other;
> - * - cpus_read_lock/unlock() to synchronize with
> - *   the cpu-hotplug-callback call sites.
> - *
> - * We guarantee that only a single cpu is being
> - * updated at any particular moment of time.
> - */
> -static DEFINE_MUTEX(microcode_mutex);
> -
>  struct ucode_cpu_info		ucode_cpu_info[NR_CPUS];
>  
>  struct cpu_info_ctx {
> @@ -323,6 +309,20 @@ void reload_early_microcode(unsigned int cpu)
>  static struct platform_device	*microcode_pdev;
>  
>  #ifdef CONFIG_MICROCODE_LATE_LOADING
> +/*
> + * Synchronization.
> + *
> + * All non cpu-hotplug-callback call sites use:
> + *
> + * - microcode_mutex to synchronize with each other;
> + * - cpus_read_lock/unlock() to synchronize with
> + *   the cpu-hotplug-callback call sites.
> + *
> + * We guarantee that only a single cpu is being
> + * updated at any particular moment of time.
> + */
> +static DEFINE_MUTEX(microcode_mutex);
> +
>  /*
>   * Late loading dance. Why the heavy-handed stomp_machine effort?
>   *
> -- 
> 2.40.1
>