Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752882AbaBZSGu (ORCPT ); Wed, 26 Feb 2014 13:06:50 -0500 Received: from mx1.redhat.com ([209.132.183.28]:4025 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752782AbaBZSGt (ORCPT ); Wed, 26 Feb 2014 13:06:49 -0500 Date: Wed, 26 Feb 2014 19:06:03 +0100 From: Oleg Nesterov To: Alex Thorlton Cc: Peter Zijlstra , Christian Borntraeger , akpm@linux-foundation.org, linux-kernel@vger.kernel.org, viro@zeniv.linux.org.uk, schwidefsky@de.ibm.com, rientjes@google.com, riel@redhat.com, pbonzini@redhat.com, mingo@kernel.org, mgorman@suse.de, kirill.shutemov@linux.intel.com, heiko.carstens@de.ibm.com, hannes@cmpxchg.org, gerald.schaefer@de.ibm.com, ebiederm@xmission.com, aarcange@redhat.com Subject: Re: + mm-revert-thp-make-madv_hugepage-check-for-mm-def_flags.patch added to -mm tree Message-ID: <20140226180603.GA25644@redhat.com> References: <530d2ce9.eikv0ULecNwxF4I5%akpm@linux-foundation.org> <530D9F50.1080400@de.ibm.com> <20140226145025.GA12571@redhat.com> <530E0306.7020601@de.ibm.com> <20140226153144.GA15527@redhat.com> <20140226165759.GB22802@laptop.programming.kicks-ass.net> <20140226172253.GQ3041@sgi.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140226172253.GQ3041@sgi.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 Suggested-by: Christian Borntraeger Signed-off-by: Oleg Nesterov 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; /* -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/