Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752653AbaBZOvY (ORCPT ); Wed, 26 Feb 2014 09:51:24 -0500 Received: from mx1.redhat.com ([209.132.183.28]:37179 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751114AbaBZOvV (ORCPT ); Wed, 26 Feb 2014 09:51:21 -0500 Date: Wed, 26 Feb 2014 15:50:25 +0100 From: Oleg Nesterov To: Christian Borntraeger Cc: akpm@linux-foundation.org, linux-kernel@vger.kernel.org, viro@zeniv.linux.org.uk, schwidefsky@de.ibm.com, rientjes@google.com, riel@redhat.com, peterz@infradead.org, 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, athorlton@sgi.com Subject: Re: + mm-revert-thp-make-madv_hugepage-check-for-mm-def_flags.patch added to -mm tree Message-ID: <20140226145025.GA12571@redhat.com> References: <530d2ce9.eikv0ULecNwxF4I5%akpm@linux-foundation.org> <530D9F50.1080400@de.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <530D9F50.1080400@de.ibm.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, 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; /* -- 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/