From 9a291a7c9428155e8e623e4a3989f8be47134df5 Mon Sep 17 00:00:00 2001 From: James Morse Date: Fri, 2 Jun 2017 14:46:46 -0700 Subject: 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 Acked-by: Punit Agrawal Acked-by: Naoya Horiguchi Cc: "Kirill A . Shutemov" Cc: [4.11.1+] Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/mm.h | 11 +++++++++++ 1 file changed, 11 insertions(+) (limited to 'include/linux/mm.h') 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, -- cgit