Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757990AbbKSISe (ORCPT ); Thu, 19 Nov 2015 03:18:34 -0500 Received: from e06smtp13.uk.ibm.com ([195.75.94.109]:35549 "EHLO e06smtp13.uk.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757284AbbKSISb (ORCPT ); Thu, 19 Nov 2015 03:18:31 -0500 X-IBM-Helo: d06dlp02.portsmouth.uk.ibm.com X-IBM-MailFrom: schwidefsky@de.ibm.com X-IBM-RcptTo: linux-kernel@vger.kernel.org;linux-s390@vger.kernel.org Date: Thu, 19 Nov 2015 09:18:08 +0100 From: Martin Schwidefsky To: Dominik Dingel Cc: linux-s390@vger.kernel.org, linux-mm@kvack.org, Andrew Morton , "Kirill A. Shutemov" , Andrea Arcangeli , David Rientjes , Eric B Munson , Naoya Horiguchi , Mel Gorman , Heiko Carstens , Christian Borntraeger , Paolo Bonzini , "Jason J. Herne" , linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/2] s390/mm: allow gmap code to retry on faulting in guest memory Message-ID: <20151119091808.5d84c8ba@mschwide> In-Reply-To: <1447890598-56860-3-git-send-email-dingel@linux.vnet.ibm.com> References: <1447890598-56860-1-git-send-email-dingel@linux.vnet.ibm.com> <1447890598-56860-3-git-send-email-dingel@linux.vnet.ibm.com> X-Mailer: Claws Mail 3.9.3 (GTK+ 2.24.23; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 15111908-0013-0000-0000-000007B2BD6B Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1881 Lines: 58 On Thu, 19 Nov 2015 00:49:58 +0100 Dominik Dingel wrote: > The userfaultfd does need FAULT_FLAG_ALLOW_RETRY to not return > VM_FAULT_SIGBUS. So we improve the gmap code to handle one > VM_FAULT_RETRY. > > Signed-off-by: Dominik Dingel > --- > arch/s390/mm/pgtable.c | 28 ++++++++++++++++++++++++---- > 1 file changed, 24 insertions(+), 4 deletions(-) > > diff --git a/arch/s390/mm/pgtable.c b/arch/s390/mm/pgtable.c > index 54ef3bc..8a0025d 100644 > --- a/arch/s390/mm/pgtable.c > +++ b/arch/s390/mm/pgtable.c > @@ -577,15 +577,22 @@ int gmap_fault(struct gmap *gmap, unsigned long gaddr, > unsigned int fault_flags) > { > unsigned long vmaddr; > - int rc; > + int rc, fault; > > + fault_flags |= FAULT_FLAG_ALLOW_RETRY; > +retry: > down_read(&gmap->mm->mmap_sem); > vmaddr = __gmap_translate(gmap, gaddr); > if (IS_ERR_VALUE(vmaddr)) { > rc = vmaddr; > goto out_up; > } > - if (fixup_user_fault(current, gmap->mm, vmaddr, fault_flags)) { > + fault = fixup_user_fault(current, gmap->mm, vmaddr, fault_flags); > + if (fault & VM_FAULT_RETRY) { > + fault_flags &= ~FAULT_FLAG_ALLOW_RETRY; > + fault_flags |= FAULT_FLAG_TRIED; > + goto retry; > + } else if (fault) { > rc = -EFAULT; > goto out_up; > } Me thinks that you want to add the retry code into fixup_user_fault itself. You basically have the same code around the three calls to fixup_user_fault. Yes, it will be a common code patch but I guess that it will be acceptable given userfaultfd as a reason. -- blue skies, Martin. "Reality continues to ruin my life." - Calvin. -- 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/