linux-kernel - Re: [PATCH v10 10/12] x86, mm, pat: Cleanup init flags in pat

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Message-ID: <20150529085920.GB31435@pd.tnic>
Date:	Fri, 29 May 2015 10:59:20 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Toshi Kani <toshi.kani@...com>
Cc:	hpa@...or.com, tglx@...utronix.de, mingo@...hat.com,
	akpm@...ux-foundation.org, arnd@...db.de, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, x86@...nel.org,
	linux-nvdimm@...ts.01.org, jgross@...e.com,
	stefan.bader@...onical.com, luto@...capital.net, hmh@....eng.br,
	yigal@...xistor.com, konrad.wilk@...cle.com, Elliott@...com,
	mcgrof@...e.com, hch@....de
Subject: Re: [PATCH v10 10/12] x86, mm, pat: Cleanup init flags in pat_init()

On Wed, May 27, 2015 at 09:19:02AM -0600, Toshi Kani wrote:
> pat_init() uses two flags, 'boot_cpu' and 'boot_pat_state', for
> tracking the boot CPU's initialization status.  'boot_pat_state'
> is also overloaded to carry the boot PAT value.
> 
> This patch cleans this up by replacing them with a new single
> flag, 'boot_cpu_done', to track the boot CPU's initialization
> status.  'boot_pat_state' is only used to carry the boot PAT
> value as a result.
> 
> Suggested-by: Thomas Gleixner <tglx@...utronix.de>
> Signed-off-by: Toshi Kani <toshi.kani@...com>
> ---
>  arch/x86/mm/pat.c |   42 ++++++++++++++++++++----------------------
>  1 file changed, 20 insertions(+), 22 deletions(-)

...

> +		rdmsrl(MSR_IA32_CR_PAT, boot_pat_state);
> +		if (!boot_pat_state) {
> +			pat_disable("PAT read returns always zero, disabled.");
> +			return;
> +		}
> +	} else if (!cpu_has_pat) {
> +		/*
> +		 * If this happens we are on a secondary CPU, but
> +		 * switched to PAT on the boot CPU. We have no way to
> +		 * undo PAT.
> +		 */
> +		pr_err("PAT enabled, but not supported by secondary CPU\n");
> +		BUG();

These could be replaced with a panic().

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
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