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Message-Id: <20180516233207.1580-2-toshi.kani@hpe.com>
Date: Wed, 16 May 2018 17:32:05 -0600
From: Toshi Kani <toshi.kani@....com>
To: mhocko@...e.com, akpm@...ux-foundation.org, tglx@...utronix.de,
mingo@...hat.com, hpa@...or.com
Cc: cpandya@...eaurora.org, linux-mm@...ck.org, x86@...nel.org,
linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
Toshi Kani <toshi.kani@....com>,
Joerg Roedel <joro@...tes.org>, stable@...r.kernel.org
Subject: [PATCH v3 1/3] 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: 28ee90fe6048 ("x86/mm: implement free pmd/pte page interfaces")
Reported-by: Joerg Roedel <joro@...tes.org>
Signed-off-by: Toshi Kani <toshi.kani@....com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Michal Hocko <mhocko@...e.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: "H. Peter Anvin" <hpa@...or.com>
Cc: Joerg Roedel <joro@...tes.org>
Cc: <stable@...r.kernel.org>
---
arch/x86/mm/pgtable.c | 19 +++++++++++++++++++
1 file changed, 19 insertions(+)
diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c
index ffc8c13c50e4..3f7180bc5f52 100644
--- a/arch/x86/mm/pgtable.c
+++ b/arch/x86/mm/pgtable.c
@@ -715,6 +715,7 @@ int pmd_clear_huge(pmd_t *pmd)
return 0;
}
+#ifdef CONFIG_X86_64
/**
* pud_free_pmd_page - Clear pud entry and free pmd page.
* @pud: Pointer to a PUD.
@@ -762,4 +763,22 @@ int pmd_free_pte_page(pmd_t *pmd)
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 */
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