From: James Morse <james.morse@xxxxxxx> 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@xxxxxxx: add vm_fault_to_errno() call to faultin_page()] suggested. Link: http://lkml.kernel.org/r/20170525171035.16359-1-james.morse@xxxxxxx [akpm@xxxxxxxxxxxxxxxxxxxx: coding-style fixes] Link: http://lkml.kernel.org/r/20170524160900.28786-1-james.morse@xxxxxxx Signed-off-by: James Morse <james.morse@xxxxxxx> Acked-by: Punit Agrawal <punit.agrawal@xxxxxxx> Acked-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx> Cc: "Kirill A . Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> [4.11.1+] Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- include/linux/mm.h | 11 +++++++++++ mm/gup.c | 20 ++++++++------------ mm/hugetlb.c | 5 +++++ 3 files changed, 24 insertions(+), 12 deletions(-) diff -puN include/linux/mm.h~mm-hugetlb-report-ehwpoison-not-efault-when-foll_hwpoison-is-specified include/linux/mm.h --- a/include/linux/mm.h~mm-hugetlb-report-ehwpoison-not-efault-when-foll_hwpoison-is-specified +++ a/include/linux/mm.h @@ -2327,6 +2327,17 @@ static inline struct page *follow_page(s #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 -puN mm/gup.c~mm-hugetlb-report-ehwpoison-not-efault-when-foll_hwpoison-is-specified mm/gup.c --- a/mm/gup.c~mm-hugetlb-report-ehwpoison-not-efault-when-foll_hwpoison-is-specified +++ a/mm/gup.c @@ -407,12 +407,10 @@ static int faultin_page(struct task_stru 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 -puN mm/hugetlb.c~mm-hugetlb-report-ehwpoison-not-efault-when-foll_hwpoison-is-specified mm/hugetlb.c --- a/mm/hugetlb.c~mm-hugetlb-report-ehwpoison-not-efault-when-foll_hwpoison-is-specified +++ a/mm/hugetlb.c @@ -4170,6 +4170,11 @@ long follow_hugetlb_page(struct mm_struc } 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; } _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
