linux-kernel - Re: [PATCHv4 07/10] kexec: Switch to __pa_symbol

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Message-ID: <20161201024103.GA32438@dhcp-128-65.nay.redhat.com>
Date:   Thu, 1 Dec 2016 10:41:03 +0800
From:   Dave Young <dyoung@...hat.com>
To:     Laura Abbott <labbott@...hat.com>
Cc:     Mark Rutland <mark.rutland@....com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Will Deacon <will.deacon@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Eric Biederman <ebiederm@...ssion.com>, x86@...nel.org,
        kexec@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-arm-kernel@...ts.infradead.org,
        Marek Szyprowski <m.szyprowski@...sung.com>
Subject: Re: [PATCHv4 07/10] kexec: Switch to __pa_symbol

Hi, Laura
On 11/29/16 at 10:55am, Laura Abbott wrote:
> 
> __pa_symbol is the correct api to get the physical address of kernel
> symbols. Switch to it to allow for better debug checking.
> 

I assume __pa_symbol is faster than __pa, but it still need some testing
on all arches which support kexec.

But seems long long ago there is a commit e3ebadd95cb in the commit log
I see below from:
"we should deprecate __pa_symbol(), and preferably __pa() too - and
 just use "virt_to_phys()" instead, which is is more readable and has
 nicer semantics."

But maybe in modern code __pa_symbol is prefered I may miss background.
virt_to_phys still sounds more readable now for me though.

> Signed-off-by: Laura Abbott <labbott@...hat.com>
> ---
> Found during review of the kernel. Untested.
> ---
>  kernel/kexec_core.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
> index 5616755..e1b625e 100644
> --- a/kernel/kexec_core.c
> +++ b/kernel/kexec_core.c
> @@ -1397,7 +1397,7 @@ void __weak arch_crash_save_vmcoreinfo(void)
>  
>  phys_addr_t __weak paddr_vmcoreinfo_note(void)
>  {
> -	return __pa((unsigned long)(char *)&vmcoreinfo_note);
> +	return __pa_symbol((unsigned long)(char *)&vmcoreinfo_note);
>  }
>  
>  static int __init crash_save_vmcoreinfo_init(void)
> -- 
> 2.7.4
> 
> 
> _______________________________________________
> kexec mailing list
> kexec@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/kexec

Thanks
Dave

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