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authorJames Morse <james.morse@arm.com>2017-06-02 14:46:46 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2017-06-02 15:07:38 -0700
commit9a291a7c9428155e8e623e4a3989f8be47134df5 (patch)
tree7cef1f6714c62ccc43431ade14559dd0be585e54
parent70feee0e1ef331b22cc51f383d532a0d043fbdcc (diff)
downloadleg-kernel-9a291a7c9428155e8e623e4a3989f8be47134df5.tar.gz
mm/hugetlb: report -EHWPOISON not -EFAULT when FOLL_HWPOISON is specified
KVM uses get_user_pages() to resolve its stage2 faults. KVM sets the FOLL_HWPOISON flag causing faultin_page() to return -EHWPOISON when it finds a VM_FAULT_HWPOISON. KVM handles these hwpoison pages as a special case. (check_user_page_hwpoison()) When huge pages are involved, this doesn't work so well. get_user_pages() calls follow_hugetlb_page(), which stops early if it receives VM_FAULT_HWPOISON from hugetlb_fault(), eventually returning -EFAULT to the caller. The step to map this to -EHWPOISON based on the FOLL_ flags is missing. The hwpoison special case is skipped, and -EFAULT is returned to user-space, causing Qemu or kvmtool to exit. Instead, move this VM_FAULT_ to errno mapping code into a header file and use it from faultin_page() and follow_hugetlb_page(). With this, KVM works as expected. This isn't a problem for arm64 today as we haven't enabled MEMORY_FAILURE, but I can't see any reason this doesn't happen on x86 too, so I think this should be a fix. This doesn't apply earlier than stable's v4.11.1 due to all sorts of cleanup. [james.morse@arm.com: add vm_fault_to_errno() call to faultin_page()] suggested. Link: http://lkml.kernel.org/r/20170525171035.16359-1-james.morse@arm.com [akpm@linux-foundation.org: coding-style fixes] Link: http://lkml.kernel.org/r/20170524160900.28786-1-james.morse@arm.com Signed-off-by: James Morse <james.morse@arm.com> Acked-by: Punit Agrawal <punit.agrawal@arm.com> Acked-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Cc: "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com> Cc: <stable@vger.kernel.org> [4.11.1+] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--include/linux/mm.h11
-rw-r--r--mm/gup.c20
-rw-r--r--mm/hugetlb.c5
3 files changed, 24 insertions, 12 deletions
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 7cb17c6b97de..b892e95d4929 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2327,6 +2327,17 @@ static inline struct page *follow_page(struct vm_area_struct *vma,
#define FOLL_REMOTE 0x2000 /* we are working on non-current tsk/mm */
#define FOLL_COW 0x4000 /* internal GUP flag */
+static inline int vm_fault_to_errno(int vm_fault, int foll_flags)
+{
+ if (vm_fault & VM_FAULT_OOM)
+ return -ENOMEM;
+ if (vm_fault & (VM_FAULT_HWPOISON | VM_FAULT_HWPOISON_LARGE))
+ return (foll_flags & FOLL_HWPOISON) ? -EHWPOISON : -EFAULT;
+ if (vm_fault & (VM_FAULT_SIGBUS | VM_FAULT_SIGSEGV))
+ return -EFAULT;
+ return 0;
+}
+
typedef int (*pte_fn_t)(pte_t *pte, pgtable_t token, unsigned long addr,
void *data);
extern int apply_to_page_range(struct mm_struct *mm, unsigned long address,
diff --git a/mm/gup.c b/mm/gup.c
index d9e6fddcc51f..b3c7214d710d 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -407,12 +407,10 @@ static int faultin_page(struct task_struct *tsk, struct vm_area_struct *vma,
ret = handle_mm_fault(vma, address, fault_flags);
if (ret & VM_FAULT_ERROR) {
- if (ret & VM_FAULT_OOM)
- return -ENOMEM;
- if (ret & (VM_FAULT_HWPOISON | VM_FAULT_HWPOISON_LARGE))
- return *flags & FOLL_HWPOISON ? -EHWPOISON : -EFAULT;
- if (ret & (VM_FAULT_SIGBUS | VM_FAULT_SIGSEGV))
- return -EFAULT;
+ int err = vm_fault_to_errno(ret, *flags);
+
+ if (err)
+ return err;
BUG();
}
@@ -723,12 +721,10 @@ retry:
ret = handle_mm_fault(vma, address, fault_flags);
major |= ret & VM_FAULT_MAJOR;
if (ret & VM_FAULT_ERROR) {
- if (ret & VM_FAULT_OOM)
- return -ENOMEM;
- if (ret & (VM_FAULT_HWPOISON | VM_FAULT_HWPOISON_LARGE))
- return -EHWPOISON;
- if (ret & (VM_FAULT_SIGBUS | VM_FAULT_SIGSEGV))
- return -EFAULT;
+ int err = vm_fault_to_errno(ret, 0);
+
+ if (err)
+ return err;
BUG();
}
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index e5828875f7bb..3eedb187e549 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -4170,6 +4170,11 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
}
ret = hugetlb_fault(mm, vma, vaddr, fault_flags);
if (ret & VM_FAULT_ERROR) {
+ int err = vm_fault_to_errno(ret, flags);
+
+ if (err)
+ return err;
+
remainder = 0;
break;
}