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 --- mm/gup.c | 20 ++++++++------------ mm/hugetlb.c | 5 +++++ 2 files changed, 13 insertions(+), 12 deletions(-) (limited to 'mm') 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; } -- cgit