Messages in this thread Patch in this message | | | Date | Wed, 26 Feb 2014 19:06:03 +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, Alex Thorlton wrote: > > + * 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 (mm_has_pgste(vma->vm_mm)) > return -EINVAL; > +#endif
The comment is not really right...
And personally I think that
@@ -504,6 +504,9 @@ static int gmap_connect_pgtable(unsigned long address, unsigned long segment, if (!pmd_present(*pmd) && __pte_alloc(mm, vma, pmd, vmaddr)) return -ENOMEM; + /* large pmds cannot yet be handled */ + if (pmd_large(*pmd)) + return -EFAULT;
change still makes sense, so that we can simply revert this s390- specific hack in hugepage_madvise().
I'd suggest the patch below on top of your changes, but I won't argue.
It would be nice to also change thp_split_mm() to not not play with mm->def_flags, but I am not sure if we can do this.
Oleg. ---
Subject: [PATCH] s390: make sure MADV_HUGEPAGE fails after s390_enable_sie()
As Christian pointed out, the recent 'Revert "thp: make MADV_HUGEPAGE check for mm->def_flags"' breaks qemu, it does QEMU_MADV_HUGEPAGE for all kvm pages but this doesn't work after s390_enable_sie/thp_split_mm.
Reported-by: Christian Borntraeger <borntraeger@de.ibm.com> Suggested-by: Christian Borntraeger <borntraeger@de.ibm.com> Signed-off-by: Oleg Nesterov <oleg@redhat.com>
diff --git a/mm/huge_memory.c b/mm/huge_memory.c index a4310a5..0e08d92 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1970,11 +1970,22 @@ int hugepage_madvise(struct vm_area_struct *vma, { switch (advice) { case MADV_HUGEPAGE: +#ifdef CONFIG_S390 + /* + * MADV_HUGEPAGE is broken after s390_enable_sie(), qemu + * blindly does madvise(MADV_HUGEPAGE) for for all kvm pages + * and expects it must fail on s390. Avoid a possible SIGSEGV + * until qemu is changed. + */ + if (mm_has_pgste(vma->vm_mm)) + return -EINVAL; +#endif /* * Be somewhat over-protective like KSM for now! */ if (*vm_flags & (VM_HUGEPAGE | VM_NO_THP)) return -EINVAL; + *vm_flags &= ~VM_NOHUGEPAGE; *vm_flags |= VM_HUGEPAGE; /*
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