linux-kernel - Re: [PATCH 2/2] Suppress false "mtrr all empty" warning message when running as VMware guest

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Date:	Wed, 24 Sep 2008 14:54:14 +0200
From:	Laurent Vivier <Laurent.Vivier@...l.net>
To:	Yan Li <elliot.li.tech@...il.com>
Cc:	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>,
	"H. Peter Anvin" <hpa@...or.com>, joerg.roedel@....com,
	rjmaomao@...il.com, Yinghai Lu <yhlu.kernel@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>, nancydreaming@...il.com
Subject: Re: [PATCH 2/2] Suppress false "mtrr all empty" warning message
	when running as VMware guest

Le mercredi 24 septembre 2008 à 20:24 +0800, Yan Li a écrit :
> Since the mtrr empty was detected very early before we can use DMI or
> PCI to check whether we are running as a VMware guest or not, we now
> only print an info there. Warning will only be issued later when we
> are sure that we are not running as a VMware guest.
> 
> mtrr_trim_uncached_memory() is modified to return meaningful codes for
> later warning decision.
> 
> Signed-off-by: Yan Li <elliot.li.tech@...il.com>
> ---
>  arch/x86/kernel/cpu/mtrr/main.c |   16 +++++++++++++++-
>  arch/x86/kernel/setup.c         |   27 ++++++++++++++++++++++++++-
>  include/asm-x86/mtrr.h          |    2 ++
>  3 files changed, 43 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/kernel/cpu/mtrr/main.c b/arch/x86/kernel/cpu/mtrr/main.c
> index b117d7f..95d1cc0 100644
> --- a/arch/x86/kernel/cpu/mtrr/main.c
> +++ b/arch/x86/kernel/cpu/mtrr/main.c
> @@ -1453,6 +1453,11 @@ static u64 __init real_trim_memory(unsigned long start_pfn,
>   * all of the memory the kernel is intending to use. If not, it'll trim any
>   * memory off the end by adjusting end_pfn, removing it from the kernel's
>   * allocation pools, warning the user with an obnoxious message.
> + *
> + * Return code:
> + * EMTRR_ALL_BLANK (-1):  not trimmed due to CPU MTRRs all blank
> + *                    0:  not trimmed due to other reasons
> + *                    1:  trimmed successfully
>   */
>  int __init mtrr_trim_uncached_memory(unsigned long end_pfn)
>  {
> @@ -1494,11 +1499,20 @@ int __init mtrr_trim_uncached_memory(unsigned long end_pfn)
>  			highest_pfn = base + size;
>  	}
>  
> -	/* kvm/qemu doesn't have mtrr set right, don't trim them all */
> +	/* kvm/qemu/VMware doesn't have mtrr set right, don't trim them all */
>  	if (!highest_pfn) {
> +#ifdef CONFIG_VMWARE_GUEST_DETECT
> +		/* the "mtrr all blank" warning will be deferred until
> +		 * after DMI scanning and we know the machine is not a
> +		 * VMware guest
> +		 */
> +		printk(KERN_INFO "CPU MTRRs all blank\n");
> +		return EMTRR_ALL_BLANK;
> +#else
>  		WARN(!kvm_para_available(), KERN_WARNING
>  				"WARNING: strange, CPU MTRRs all blank?\n");
>  		return 0;
> +#endif
>  	}

perhaps something like:

#ifdef CONFIG_VMWARE_GUEST_DETECT
 		WARN(!kvm_para_available() && !is_vmware_guest(), KERN_WARNING
				"WARNING: strange, CPU MTRRs all blank?\n");
#else
 		WARN(!kvm_para_available(), KERN_WARNING
  				"WARNING: strange, CPU MTRRs all blank?\n");
...

???

Laurent
-- 
----------------- Laurent.Vivier@...l.net  ------------------
  "La perfection est atteinte non quand il ne reste rien à
ajouter mais quand il ne reste rien à enlever." Saint Exupéry

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