linux-kernel - [PATCH] x86/i386: Check PSE bit before using PAGE_KERNEL

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Date:	Thu, 31 May 2012 15:40:18 -0400
From:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:	konrad@...nok.org, linux-kernel@...r.kernel.org, x86@...nel.org,
	hpa@...or.com, mingo@...hat.com, tglx@...utronix.de
Cc:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>, stable@...nel.org
Subject: [PATCH] x86/i386: Check PSE bit before using PAGE_KERNEL_LARGE.

During bootup we would unconditionally do this on any
machine that was built with CONFIG_NUMA=y on i386:

setup_arch
  \-initmem_init
      \-x86_numa_init (with dummy_init as callback)
          \- init_alloc_remap
               \- set_pmd_pfn (with PAGE_PSE)

without checking to see if the CPU supports PSE. This
patch adds that and also allows the init_alloc_remap function
to properly work by falling back on PTEs.

CC: stable@...nel.org
Tested-by: William Dauchy <wdauchy@...il.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
---
 arch/x86/mm/pgtable_32.c |   25 ++++++++++++++++++++++++-
 1 files changed, 24 insertions(+), 1 deletions(-)

diff --git a/arch/x86/mm/pgtable_32.c b/arch/x86/mm/pgtable_32.c
index a69bcb8..9fd4abc 100644
--- a/arch/x86/mm/pgtable_32.c
+++ b/arch/x86/mm/pgtable_32.c
@@ -86,7 +86,30 @@ void set_pmd_pfn(unsigned long vaddr, unsigned long pfn, pgprot_t flags)
 	}
 	pud = pud_offset(pgd, vaddr);
 	pmd = pmd_offset(pud, vaddr);
-	set_pmd(pmd, pfn_pmd(pfn, flags));
+
+	if ((!cpu_has_pse) && (pgprot_val(flags) & _PAGE_PSE)) {
+		pte_t *pte;
+		int i;
+
+		pgprot_val(flags) &= ~_PAGE_PSE;
+
+		/*
+		 * This is run _after_ initial memory mapped so the
+		 * PTE page are allocated - but we check it just in case.
+		 */
+		if (pmd_none(*pmd)) {
+			printk(KERN_WARNING "set_pmd_pfn: pmd_none\n");
+			return;
+		}
+
+		pte = (pte_t *)pmd_page_vaddr(*pmd);
+		for (i = 0; i < PTRS_PER_PTE; i++) {
+			set_pte(pte, pfn_pte(pfn + i, flags));
+			pte++;
+		}
+	} else
+		set_pmd(pmd, pfn_pmd(pfn, flags));
+
 	/*
 	 * It's enough to flush this one mapping.
 	 * (PGE mappings get flushed as well)
-- 
1.7.7.6

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