linux-kernel - Re: [crash, bisected] Re: [PATCH 3/4] x86

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Message-ID: <485ADBCF.5040101@goop.org>
Date:	Thu, 19 Jun 2008 15:21:03 -0700
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Mike Travis <travis@....com>
CC:	Rusty Russell <rusty@...tcorp.com.au>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Christoph Lameter <clameter@....com>,
	Jack Steiner <steiner@....com>
Subject: Re: [crash, bisected] Re: [PATCH 3/4] x86_64: Fold pda into per cpu
 area

Mike Travis wrote:
> Jeremy Fitzhardinge wrote:
>
>   
>> Why not use the real pda for all cpus?
>>     
>
> Yeah, I figured that out after doing some more thinking... ;-)
>
>   
>> Do you move the boot-cpu's per-cpu data? (Please don't)  If not, you can
>> just use percpu__pda from the start without having to do anything else,
>> and then set up %gs pointing to the pda base for each secondary cpu.
>>     
>
> The problem is that the static percpu area is removed as it lies
> in the initdata section, so the pda is removed as well.
>   

Well, that's easy to fix...

> But I took your suggestion to move the fixup to before secondary_startup.
>
> Below is a revised version. 

(Incremental diffs are easier to review and work with.)

>  It builds but I'll have to test it tomorrow.
> Note the addition of:
>
> +       initial_pda = (unsigned long)get_percpu_pda(cpu);
>
> in do_boot_cpu.
>
> I'm not sure yet what to put into acpi_save_state_mem:
>
>         initial_code = (unsigned long)wakeup_long64;
> +       /* ZZZ initial_pda = (unsigned long)?; */
>   

You'll need to change wakeup_long64 to load the right value into the 
GS_BASE msr anyway.

    J
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