linux-kernel - Re: [patch 04/26] Xen-paravirt_ops: Add pagetable accessors to pack and unpack pagetable entries

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Message-ID: <20070316093844.GT23174@elte.hu>
Date:	Fri, 16 Mar 2007 10:38:44 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
Cc:	Andi Kleen <ak@....de>, Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, virtualization@...ts.osdl.org,
	xen-devel@...ts.xensource.com, Chris Wright <chrisw@...s-sol.org>,
	Zachary Amsden <zach@...are.com>,
	Rusty Russell <rusty@...tcorp.com.au>
Subject: Re: [patch 04/26] Xen-paravirt_ops: Add pagetable accessors to pack and unpack pagetable entries


* Jeremy Fitzhardinge <jeremy@...p.org> wrote:

> Add a set of accessors to pack, unpack and modify page table entries 
> (at all levels).  This allows a paravirt implementation to control the 
> contents of pgd/pmd/pte entries.  For example, Xen uses this to 
> convert the (pseudo-)physical address into a machine address when 
> populating a pagetable entry, and converting back to pphys address 
> when an entry is read.

looks good.

Acked-by: Ingo Molnar <mingo@...e.hu>

only some minor style nits:

> +static inline unsigned long long native_pgd_val(pgd_t pgd)
> +{
> +	return pgd.pgd;
> +}
> +static inline unsigned long long native_pmd_val(pmd_t pmd)
> +{
> +	return pmd.pmd;
> +}
> +static inline unsigned long long native_pte_val(pte_t pte)
> +{
> +	return pte.pte_low | ((unsigned long long)pte.pte_high << 32);
> +}
> +static inline pgd_t native_make_pgd(unsigned long long val)
> +{
> +	return (pgd_t) { val };
> +}
> +static inline pmd_t native_make_pmd(unsigned long long val)
> +{
> +	return (pmd_t) { val };
> +}
> +static inline pte_t native_make_pte(unsigned long long val)
> +{
> +	return (pte_t) { .pte_low = val, .pte_high = (val >> 32) } ;
> +}

missing newlines between inline functions.

> +#ifndef CONFIG_PARAVIRT
> +#define pmd_val(x)	native_pmd_val(x)
> +#define __pmd(x)	native_make_pmd(x)
> +#endif	/* !CONFIG_PARAVIRT */

no need for the closing !CONFIG_PARAVIRT comment: this define is 2 lines 
long so it's not that hard to find the start of the block. We typically 
do the /* !CONFIG_XX */ comment only for larger blocks, and when 
multiple #endif's intermix.

> +static inline unsigned long native_pgd_val(pgd_t pgd)
> +{
> +	return pgd.pgd;
> +}
> +static inline unsigned long native_pte_val(pte_t pte)
> +{
> +	return pte.pte_low;
> +}
> +static inline pgd_t native_make_pgd(unsigned long val)
> +{
> +	return (pgd_t) { val };
> +}
> +static inline pte_t native_make_pte(unsigned long val)
> +{
> +	return (pte_t) { .pte_low = val };
> +}

newlines.

>  #define HPAGE_SHIFT	22
>  #include <asm-generic/pgtable-nopmd.h>
> -#endif
> +#endif	/* CONFIG_X86_PAE */

(for example here the #endif comment is justified.)

	Ingo
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