linux-kernel - Re: [patch 2/4] x86: PAT followup - Remove KERNPG

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Message-ID: <20080117001823.GA20383@linux-os.sc.intel.com>
Date:	Wed, 16 Jan 2008 16:18:24 -0800
From:	Venki Pallipadi <venkatesh.pallipadi@...el.com>
To:	Mika Penttilä <mika.penttila@...umbus.fi>
Cc:	venkatesh.pallipadi@...el.com, ak@....de, ebiederm@...ssion.com,
	rdreier@...co.com, torvalds@...ux-foundation.org, gregkh@...e.de,
	airlied@...net.ie, davej@...hat.com, mingo@...e.hu,
	tglx@...utronix.de, hpa@...or.com, akpm@...ux-foundation.org,
	arjan@...radead.org, jesse.barnes@...el.com, davem@...emloft.net,
	linux-kernel@...r.kernel.org,
	Suresh Siddha <suresh.b.siddha@...el.com>
Subject: Re: [patch 2/4] x86: PAT followup - Remove KERNPG_TABLE from pte entry

On Wed, Jan 16, 2008 at 10:14:00AM +0200, Mika Penttilä wrote:
> venkatesh.pallipadi@...el.com kirjoitti:
> >KERNPG_TABLE was a bug in earlier patch. Remove it from pte.
> >pte_val() check is redundant as this routine is called immediately after a
> >ptepage is allocated afresh.
> >
> >Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@...el.com>
> >Signed-off-by: Suresh Siddha <suresh.b.siddha@...el.com>
> >
> >Index: linux-2.6.git/arch/x86/mm/init_64.c
> >===================================================================
> >--- linux-2.6.git.orig/arch/x86/mm/init_64.c	2008-01-15 
> >11:02:23.000000000 -0800
> >+++ linux-2.6.git/arch/x86/mm/init_64.c	2008-01-15 
> >11:06:37.000000000 -0800
> >@@ -541,9 +541,6 @@
> > 		if (address >= end)
> > 			break;
> > 
> >-		if (pte_val(*pte))
> >-			continue;
> >-
> > 		/* Nothing to map. Map the null page */
> > 		if (!(address & (~PAGE_MASK)) &&
> > 		    (address + PAGE_SIZE <= end) &&
> >@@ -561,9 +558,9 @@
> > 		}
> > 
> > 		if (exec)
> >-			entry = _PAGE_NX|_KERNPG_TABLE|_PAGE_GLOBAL|address;
> >+			entry = _PAGE_NX|_PAGE_GLOBAL|address;
> > 		else
> >-			entry = _KERNPG_TABLE|_PAGE_GLOBAL|address;
> >+			entry = _PAGE_GLOBAL|address;
> > 		entry &= __supported_pte_mask;
> > 		set_pte(pte, __pte(entry));
> > 	}
> >
> >  
> 
> Hmm then what's the point of mapping not present 4k pages for valid mem 
> here?
> 

Ingo,

Below incremental patch fixes this pte entry setting correctly. Thanks to
Mika for catching this.

Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@...el.com>

Index: linux-2.6.git/arch/x86/mm/init_64.c
===================================================================
--- linux-2.6.git.orig/arch/x86/mm/init_64.c	2008-01-16 03:38:32.000000000 -0800
+++ linux-2.6.git/arch/x86/mm/init_64.c	2008-01-16 03:51:34.000000000 -0800
@@ -515,9 +515,9 @@
 		}
 
 		if (exec)
-			entry = _PAGE_NX|_PAGE_GLOBAL|address;
+			entry = __PAGE_KERNEL_EXEC | _PAGE_GLOBAL | address;
 		else
-			entry = _PAGE_GLOBAL|address;
+			entry = __PAGE_KERNEL | _PAGE_GLOBAL | address;
 		entry &= __supported_pte_mask;
 		set_pte(pte, __pte(entry));
 	}

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