Commit f967db0b authored Jun 27, 2018 by Toshi Kani Committed by Thomas Gleixner Jul 04, 2018

x86/mm: Disable ioremap free page handling on x86-PAE



ioremap() supports pmd mappings on x86-PAE.  However, kernel's pmd
tables are not shared among processes on x86-PAE.  Therefore, any
update to sync'd pmd entries need re-syncing.  Freeing a pte page
also leads to a vmalloc fault and hits the BUG_ON in vmalloc_sync_one().

Disable free page handling on x86-PAE.  pud_free_pmd_page() and
pmd_free_pte_page() simply return 0 if a given pud/pmd entry is present.
This assures that ioremap() does not update sync'd pmd entries at the
cost of falling back to pte mappings.

Fixes: 28ee90fe ("x86/mm: implement free pmd/pte page interfaces")
Reported-by: Joerg Roedel <joro@8bytes.org>
Signed-off-by: Toshi Kani <toshi.kani@hpe.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: mhocko@suse.com
Cc: akpm@linux-foundation.org
Cc: hpa@zytor.com
Cc: cpandya@codeaurora.org
Cc: linux-mm@kvack.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: stable@vger.kernel.org
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: <stable@vger.kernel.org>
Link: https://lkml.kernel.org/r/20180627141348.21777-2-toshi.kani@hpe.com

parent 021c9179

arch/x86/mm/pgtable.c

+19 −0

Original line number	Original line	Diff line number	Diff line
	@@ -719,6 +719,7 @@ int pmd_clear_huge(pmd_t *pmd)
	return 0;		return 0;
	}		}

			#ifdef CONFIG_X86_64
	/**		/**
	* pud_free_pmd_page - Clear pud entry and free pmd page.		* pud_free_pmd_page - Clear pud entry and free pmd page.
	* @pud: Pointer to a PUD.		* @pud: Pointer to a PUD.
	@@ -766,4 +767,22 @@ int pmd_free_pte_page(pmd_t *pmd)

	return 1;		return 1;
	}		}

			#else /* !CONFIG_X86_64 */

			int pud_free_pmd_page(pud_t *pud)
			{
			return pud_none(*pud);
			}

			/*
			* Disable free page handling on x86-PAE. This assures that ioremap()
			* does not update sync'd pmd entries. See vmalloc_sync_one().
			*/
			int pmd_free_pte_page(pmd_t *pmd)
			{
			return pmd_none(*pmd);
			}

			#endif /* CONFIG_X86_64 */
	#endif /* CONFIG_HAVE_ARCH_HUGE_VMAP */		#endif /* CONFIG_HAVE_ARCH_HUGE_VMAP */

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