Christian Borntraeger wrote:
> On 26/02/14 15:50, Oleg Nesterov wrote:
> [...]
>
> >> 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
> > +
>
> Ifdefs are ugly
IS_ENABLED(CONFIG_S390) should help with this.
--
Kirill A. Shutemov
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