[PATCH 7/7] HWPOISON, hugetlb: fix hard offline for hugepage backed KVM guest

[Naoya Horiguchi]

When a qemu-kvm process touches HWPOISONed pages,
we expect that a SIGBUS signal causes MCE on the guest OS.
But currently it doesn't work on a hugepage backed KVM guest
because is_hwpoison_address() can't detect the HWPOISON entry
on PMD and the guest repeats page fault infinitely.

This patch fixes it.

Signed-off-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
Cc: Huang Ying <ying.huang@xxxxxxxxx>
---
 include/linux/swapops.h |   12 ++++++++++++
 mm/hugetlb.c            |    4 +++-
 mm/memory-failure.c     |    2 +-
 3 files changed, 16 insertions(+), 2 deletions(-)

diff --git v2.6.38-rc1/include/linux/swapops.h v2.6.38-rc1/include/linux/swapops.h
index a220ef5..2c1a942 100644
--- v2.6.38-rc1/include/linux/swapops.h
+++ v2.6.38-rc1/include/linux/swapops.h
@@ -177,3 +177,15 @@ extern void migration_hugepage_entry_wait(struct mm_struct *mm, pmd_t *pmd,
 static inline void migration_hugepage_entry_wait(struct mm_struct *mm,
 				 pmd_t *pmd, unsigned long address) { }
 #endif
+
+#if defined(CONFIG_MEMORY_FAILURE) && defined(CONFIG_HUGETLB_PAGE)
+extern int is_hugetlb_entry_hwpoisoned(pte_t pte);
+#else
+static inline int is_hugetlb_entry_hwpoisoned(pte_t pte)
+{
+	return 0;
+}
+#endif
+
+
+
diff --git v2.6.38-rc1/mm/hugetlb.c v2.6.38-rc1/mm/hugetlb.c
index b777c81..c65922e 100644
--- v2.6.38-rc1/mm/hugetlb.c
+++ v2.6.38-rc1/mm/hugetlb.c
@@ -2185,7 +2185,8 @@ static int is_hugetlb_entry_migration(pte_t pte)
 		return 0;
 }
 
-static int is_hugetlb_entry_hwpoisoned(pte_t pte)
+#ifdef CONFIG_MEMORY_FAILURE
+int is_hugetlb_entry_hwpoisoned(pte_t pte)
 {
 	swp_entry_t swp;
 
@@ -2197,6 +2198,7 @@ static int is_hugetlb_entry_hwpoisoned(pte_t pte)
 	} else
 		return 0;
 }
+#endif
 
 void __unmap_hugepage_range(struct vm_area_struct *vma, unsigned long start,
 			    unsigned long end, struct page *ref_page)
diff --git v2.6.38-rc1/mm/memory-failure.c v2.6.38-rc1/mm/memory-failure.c
index eed1846..8ee5038 100644
--- v2.6.38-rc1/mm/memory-failure.c
+++ v2.6.38-rc1/mm/memory-failure.c
@@ -1461,7 +1461,7 @@ int is_hwpoison_address(unsigned long addr)
 	pmdp = pmd_offset(pudp, addr);
 	pmd = *pmdp;
 	if (!pmd_present(pmd) || pmd_large(pmd))
-		return 0;
+		return is_hugetlb_entry_hwpoisoned(*(pte_t *)pmdp);
 	ptep = pte_offset_map(pmdp, addr);
 	pte = *ptep;
 	pte_unmap(ptep);
-- 
1.7.3.4

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