linux-kernel - Re: [PARAVIRT/x86] BUGFIX: Put a missing paravirt_release_pmd in pgd

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Date:	Thu, 05 Feb 2009 22:52:13 -0800
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	akataria@...are.com
CC:	Ingo Molnar <mingo@...e.hu>, "H. Peter Anvin" <hpa@...or.com>,
	the arch/x86 maintainers <x86@...nel.org>,
	Zach Amsden <zach@...are.com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Rohit Jain <rjain@...are.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PARAVIRT/x86] BUGFIX: Put a missing paravirt_release_pmd in
 pgd_dtor

Alok Kataria wrote:
> As it affects only VMI, instead of adding another callback, i have
> hooked on the paravirt_pgd_free call for vmi to release the pgd page.
> Below is the patch. I will run some overnight tests with this patch and
> get back if there are any errors.
>   

I'd forgotten that I'd already added pgd_alloc/pgd_free.  So, yes, just 
use pgd_free.

>> But either way, calling release_pmd here is wrong, since its only meant 
>> to be applied to pmds,
>>     
> Maybe i misunderstand, but that's how it used to work before that
> commit, we had a single call to release_*pd*, no ?
>   

I rearranged things, but I don't remember the details.  I think pd was 
being overloaded for both pgd and pmd, and I split it out so there was a 
specific function for each level.

>>  and it would break the Xen code.
>>     
>
> i see xen doesn't define the alloc_pmd_clone call. 
>   

It defines alloc_pmd, but has no need for alloc_pmd_clone (there's no 
shadow pagetable, so there's nothing to sync).  Zach added specifically 
for vmi's use.

    J
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