Re: [PATCH] i386: modified CONFIG_PHYSICAL_ALIGN

[Jeremy Fitzhardinge <jeremy@goop.org>]

Rusty Russell wrote:
> On Tue, 2007-08-14 at 05:29 +0200, Andi Kleen wrote:
>   
>> On Tue, Aug 14, 2007 at 09:55:50AM +0900, Yoshimi Ichiyanagi wrote:
>>
>> How is this related to virtualization?
>>
>>     
>>> The problem is, if you compile x86_64 kernel, the value of 
>>> CONFIG_PHYSICAL_ALIGN will be fixed, and the next time you compile i386 
>>> kernel, previous CONFIG_PHYSICAL_ALIGN value of x86_64(default: 2MB) will 
>>> be used by default.
>>>       
>> 2/4MB is better for i386 too for PAE/non PAE because
>> it will use less TLB entries. I guess it's better to just change
>> the defaults.
>>
>> Anyways, both values should work, or did you see 
>> failures?
>>     
>
> I had this problem too: Lguest assumes 1MB when loading bzImages, and
> the only time that gets changed is when building from an x86-64 config.
> I considered it purely an lguest issue.
>
> The correct fix is to have lguest run bzImages rather than trying to
> unpack them itself, but that requires a bootloader change, and the
> proposals to do that got lost in a flurry of far more ambitious patches.
>
> Jeremy would know the status of that work...
>   

A bit stalled.  The format I proposed could theoretically break some
bootloaders, and Eric has been too busy to talk about it.  But we'll
need to give it another go soon.

    J