From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f200.google.com (mail-pf0-f200.google.com [209.85.192.200]) by kanga.kvack.org (Postfix) with ESMTP id 4AFBE6B02F4 for ; Thu, 25 May 2017 13:11:27 -0400 (EDT) Received: by mail-pf0-f200.google.com with SMTP id m5so236642403pfc.1 for ; Thu, 25 May 2017 10:11:27 -0700 (PDT) Received: from foss.arm.com (foss.arm.com. [217.140.101.70]) by mx.google.com with ESMTP id d71si27232448pgc.68.2017.05.25.10.11.25 for ; Thu, 25 May 2017 10:11:26 -0700 (PDT) From: James Morse Subject: [PATCH v2] mm/hugetlb: Report -EHWPOISON not -EFAULT when FOLL_HWPOISON is specified Date: Thu, 25 May 2017 18:10:35 +0100 Message-Id: <20170525171035.16359-1-james.morse@arm.com> Sender: owner-linux-mm@kvack.org List-ID: To: linux-mm@kvack.org Cc: "Kirill A . Shutemov" , Andrew Morton , Punit Agrawal , James Morse , Naoya Horiguchi 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. 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(), follow_hugetlb_page() and faultin_page(). With this, KVM works as expected. CC: Punit Agrawal CC: Naoya Horiguchi Signed-off-by: James Morse --- Changes since v1: * Fixed checkpatch warnings (oops, wrong file) * Added vm_fault_to_errno() call to faultin_page() as Naoya Horiguchi suggested. 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. My best offer is: Cc: # 4.11.1 include/linux/mm.h | 11 +++++++++++ mm/gup.c | 20 ++++++++------------ mm/hugetlb.c | 5 +++++ 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 @@ int fixup_user_fault(struct task_struct *tsk, struct mm_struct *mm, 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; } -- 2.11.0 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org