linux-kernel - Re: [patch 05/23] x86/apic: Make disable x2apic work really

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Message-ID: <20150116111758.GF18880@pd.tnic>
Date:	Fri, 16 Jan 2015 12:17:58 +0100
From:	Borislav Petkov <bp@...en8.de>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Jiang Liu <jiang.liu@...ux.intel.com>,
	Joerg Roedel <joro@...tes.org>, x86@...nel.org,
	Tony Luck <tony.luck@...el.com>
Subject: Re: [patch 05/23] x86/apic: Make disable x2apic work really

On Thu, Jan 15, 2015 at 09:22:16PM -0000, Thomas Gleixner wrote:
> If x2apic_preenabled is not enabled, then disable_x2apic() is not
> called from various places which results in x2apic_disabled not being
> set. So other code pathes can happily reenable the x2apic.
> 
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> ---
>  arch/x86/kernel/apic/apic.c |   14 +++++---------
>  1 file changed, 5 insertions(+), 9 deletions(-)
> 
> Index: tip/arch/x86/kernel/apic/apic.c
> ===================================================================
> --- tip.orig/arch/x86/kernel/apic/apic.c
> +++ tip/arch/x86/kernel/apic/apic.c
> @@ -1479,8 +1479,6 @@ static bool nox2apic __initdata;
>  
>  #ifdef CONFIG_X86_X2APIC
>  int x2apic_mode;
> -/* x2apic enabled before OS handover */
> -static int x2apic_preenabled;
>  static int x2apic_disabled;
>  static int __init setup_nox2apic(char *str)
>  {
> @@ -1535,18 +1533,19 @@ static __init void disable_x2apic(void)
>  			setup_clear_cpu_cap(X86_FEATURE_X2APIC);
>  		}
>  
> -		x2apic_disabled = 1;
>  		x2apic_mode = 0;

Should we move out that write to x2apic_mode too?

>  
>  		register_lapic_address(mp_lapic_addr);
>  	}
> +
> +	x2apic_disabled = 1;

i.e., here?

Just in case.

-- 
Regards/Gruss,
    Boris.

Sent from a fat crate under my desk. Formatting is fine.
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