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From: Toshi Kani <toshi.kani@hpe.com>
To: mhocko@suse.com, akpm@linux-foundation.org, tglx@linutronix.de,
	mingo@redhat.com, hpa@zytor.com
Cc: cpandya@codeaurora.org, linux-mm@kvack.org, x86@kernel.org,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, Toshi Kani <toshi.kani@hpe.com>,
	Joerg Roedel <joro@8bytes.org>,
	stable@vger.kernel.org
Subject: [PATCH v3 1/3] x86/mm: disable ioremap free page handling on x86-PAE
Date: Wed, 16 May 2018 17:32:05 -0600	[thread overview]
Message-ID: <20180516233207.1580-2-toshi.kani@hpe.com> (raw)
In-Reply-To: <20180516233207.1580-1-toshi.kani@hpe.com>

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@8bytes.org>
Signed-off-by: Toshi Kani <toshi.kani@hpe.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: <stable@vger.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 */

  reply	other threads:[~2018-05-16 23:33 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-16 23:32 [PATCH v3 0/3] fix free pmd/pte page handlings on x86 Toshi Kani
2018-05-16 23:32 ` Toshi Kani [this message]
2018-05-16 23:32 ` [PATCH v3 2/3] ioremap: Update pgtable free interfaces with addr Toshi Kani
2018-05-17  6:47   ` Michal Hocko
2018-05-17 14:32     ` Kani, Toshi
2018-05-16 23:32 ` [PATCH v3 3/3] x86/mm: add TLB purge to free pmd/pte page interfaces Toshi Kani
2018-05-29 14:44   ` Joerg Roedel
2018-05-29 16:10     ` Kani, Toshi
2018-05-30  4:59       ` joro
2018-05-30 15:39         ` Kani, Toshi
2018-06-24 13:19 ` [PATCH v3 0/3] fix free pmd/pte page handlings on x86 Thomas Gleixner
2018-06-25 14:56   ` Kani, Toshi
2018-06-25 17:53     ` Michal Hocko
2018-06-25 21:15       ` Kani, Toshi
2018-06-26  6:35         ` Michal Hocko
2018-06-26  8:45           ` Thomas Gleixner
2018-06-26  8:54             ` Michal Hocko
2018-06-26 15:25               ` Kani, Toshi

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