linux-kernel - Re: [PATCH v2 RESEND 1/2] x86/UV: Introduce a helper function to check UV system at earlier stage

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Date:   Thu, 14 Sep 2017 15:29:52 +0800
From:   Baoquan He <bhe@...hat.com>
To:     linux-kernel@...r.kernel.org, x86@...nel.org
Cc:     mingo@...hat.com, tglx@...utronix.de, hpa@...or.com,
        thgarnie@...gle.com, keescook@...omium.org,
        akpm@...ux-foundation.org, yamada.masahiro@...ionext.com,
        rja@....com, frank.ramsay@....com, dyoung@...hat.com
Subject: Re: [PATCH v2 RESEND 1/2] x86/UV: Introduce a helper function to
 check UV system at earlier stage

Add Dave to the CC list, he may have concerns about the code change.

On 09/07/17 at 03:42pm, Baoquan He wrote:
> The BIOS on SGI UV system will report a UV system table which describes
> specific firmware capabilities available to the Linux kernel at runtime.
> This UV system table only exists on SGI UV system. And it's detected
> in efi_init() which is at very early stage.
> 
> So introduce a new helper function is_early_uv_system() to identify if
> a system is UV system. Later we will use it to check if the running
> system is UV system in mm KASLR code.
> 
> Signed-off-by: Baoquan He <bhe@...hat.com>
> Acked-by: Mike Travis <travis@....com>
> ---
>  arch/x86/include/asm/uv/uv.h | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/arch/x86/include/asm/uv/uv.h b/arch/x86/include/asm/uv/uv.h
> index b5a32231abd8..93d7ad8763ba 100644
> --- a/arch/x86/include/asm/uv/uv.h
> +++ b/arch/x86/include/asm/uv/uv.h
> @@ -18,6 +18,11 @@ extern void uv_nmi_init(void);
>  extern void uv_system_init(void);
>  extern const struct cpumask *uv_flush_tlb_others(const struct cpumask *cpumask,
>  						 const struct flush_tlb_info *info);
> +#include <linux/efi.h>
> +static inline int is_early_uv_system(void)
> +{
> +	return !((efi.uv_systab == EFI_INVALID_TABLE_ADDR) || !efi.uv_systab);
> +}
>  
>  #else	/* X86_UV */
>  
> @@ -30,6 +35,7 @@ static inline const struct cpumask *
>  uv_flush_tlb_others(const struct cpumask *cpumask,
>  		    const struct flush_tlb_info *info)
>  { return cpumask; }
> +static inline int is_early_uv_system(void)	{ return 0; }
>  
>  #endif	/* X86_UV */
>  
> -- 
> 2.5.5
>