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>
diff --git a/mm/gup.c b/mm/gup.c
index d9e6fdd..b3c7214 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -407,12 +407,10 @@
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 @@
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();
}