Messages in this thread Patch in this message | | | Date | Wed, 26 Feb 2014 15:50:25 +0100 | From | Oleg Nesterov <> | Subject | Re: + mm-revert-thp-make-madv_hugepage-check-for-mm-def_flags.patch added to -mm tree |
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On 02/26, Christian Borntraeger wrote: > > On 26/02/14 00:53, akpm@linux-foundation.org wrote: > > Subject: + mm-revert-thp-make-madv_hugepage-check-for-mm-def_flags.patch added to -mm tree > > To: athorlton@sgi.com,aarcange@redhat.com,borntraeger@de.ibm.com,ebiederm@xmission.com,gerald.schaefer@de.ibm.com,hannes@cmpxchg.org,heiko.carstens@de.ibm.com,kirill.shutemov@linux.intel.com,mgorman@suse.de,mingo@kernel.org,oleg@redhat.com,pbonzini@redhat.com,peterz@infradead.org,riel@redhat.com,rientjes@google.com,schwidefsky@de.ibm.com,viro@zeniv.linux.org.uk > > From: akpm@linux-foundation.org > > Date: Tue, 25 Feb 2014 15:53:13 -0800 > > > > > > The patch titled > > Subject: mm: revert "thp: make MADV_HUGEPAGE check for mm->def_flags" > > has been added to the -mm tree. Its filename is > > mm-revert-thp-make-madv_hugepage-check-for-mm-def_flags.patch > > > > This patch should soon appear at > > http://ozlabs.org/~akpm/mmots/broken-out/mm-revert-thp-make-madv_hugepage-check-for-mm-def_flags.patch > > and later at > > http://ozlabs.org/~akpm/mmotm/broken-out/mm-revert-thp-make-madv_hugepage-check-for-mm-def_flags.patch > > > NAK. > > Since 2012 qemu does call "qemu_madvise(new_block->host, size, QEMU_MADV_HUGEPAGE);" for all kvm pages. > (commit ad0b5321f1f797274603ebbe20108b0750baee94 Call MADV_HUGEPAGE for guest RAM allocations) so this > breaks any recent kvm guest on s390.
Well, I can't really discuss the changes in arch/s390.
But perhaps qemu can be changed to avoid MADV_HUGEPAGE on s390 ? Otherwise I'd suggest the change below.
Oleg.
--- x/mm/huge_memory.c +++ x/mm/huge_memory.c @@ -1968,8 +1968,6 @@ out: int hugepage_madvise(struct vm_area_struct *vma, unsigned long *vm_flags, int advice) { - struct mm_struct *mm = vma->vm_mm; - switch (advice) { case MADV_HUGEPAGE: /* @@ -1977,8 +1975,16 @@ int hugepage_madvise(struct vm_area_stru */ if (*vm_flags & (VM_HUGEPAGE | VM_NO_THP)) return -EINVAL; - if (mm->def_flags & VM_NOHUGEPAGE) + +/* + * MADV_HUGEPAGE after PRCTL_THP_DISABLE is broken on s390 because + * qemu blindly does madvise(MADV_HUGEPAGE) after s390_enable_sie(). + */ +#ifdef CONFIG_S390 + if (vma->vm_mm->def_flags & VM_NOHUGEPAGE) return -EINVAL; +#endif + *vm_flags &= ~VM_NOHUGEPAGE; *vm_flags |= VM_HUGEPAGE; /*
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