From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752438AbeEQLHv (ORCPT ); Thu, 17 May 2018 07:07:51 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:53264 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752391AbeEQLHq (ORCPT ); Thu, 17 May 2018 07:07:46 -0400 From: Laurent Dufour To: akpm@linux-foundation.org, mhocko@kernel.org, peterz@infradead.org, kirill@shutemov.name, ak@linux.intel.com, dave@stgolabs.net, jack@suse.cz, Matthew Wilcox , khandual@linux.vnet.ibm.com, aneesh.kumar@linux.vnet.ibm.com, benh@kernel.crashing.org, mpe@ellerman.id.au, paulus@samba.org, Thomas Gleixner , Ingo Molnar , hpa@zytor.com, Will Deacon , Sergey Senozhatsky , sergey.senozhatsky.work@gmail.com, Andrea Arcangeli , Alexei Starovoitov , kemi.wang@intel.com, Daniel Jordan , David Rientjes , Jerome Glisse , Ganesh Mahendran , Minchan Kim , Punit Agrawal , vinayak menon , Yang Shi Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, haren@linux.vnet.ibm.com, npiggin@gmail.com, bsingharora@gmail.com, paulmck@linux.vnet.ibm.com, Tim Chen , linuxppc-dev@lists.ozlabs.org, x86@kernel.org Subject: [PATCH v11 25/26] powerpc/mm: add speculative page fault Date: Thu, 17 May 2018 13:06:32 +0200 X-Mailer: git-send-email 2.7.4 In-Reply-To: <1526555193-7242-1-git-send-email-ldufour@linux.vnet.ibm.com> References: <1526555193-7242-1-git-send-email-ldufour@linux.vnet.ibm.com> X-TM-AS-GCONF: 00 x-cbid: 18051711-0020-0000-0000-0000041E3570 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18051711-0021-0000-0000-000042B35787 Message-Id: <1526555193-7242-26-git-send-email-ldufour@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2018-05-17_05:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 impostorscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1709140000 definitions=main-1805170100 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This patch enable the speculative page fault on the PowerPC architecture. This will try a speculative page fault without holding the mmap_sem, if it returns with VM_FAULT_RETRY, the mmap_sem is acquired and the traditional page fault processing is done. The speculative path is only tried for multithreaded process as there is no risk of contention on the mmap_sem otherwise. Signed-off-by: Laurent Dufour --- arch/powerpc/mm/fault.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c index ef268d5d9db7..d7b5742ffb2b 100644 --- a/arch/powerpc/mm/fault.c +++ b/arch/powerpc/mm/fault.c @@ -465,6 +465,21 @@ static int __do_page_fault(struct pt_regs *regs, unsigned long address, if (is_exec) flags |= FAULT_FLAG_INSTRUCTION; + /* + * Try speculative page fault before grabbing the mmap_sem. + * The Page fault is done if VM_FAULT_RETRY is not returned. + * But if the memory protection keys are active, we don't know if the + * fault is due to key mistmatch or due to a classic protection check. + * To differentiate that, we will need the VMA we no more have, so + * let's retry with the mmap_sem held. + */ + fault = handle_speculative_fault(mm, address, flags); + if (fault != VM_FAULT_RETRY && (IS_ENABLED(CONFIG_PPC_MEM_KEYS) && + fault != VM_FAULT_SIGSEGV)) { + perf_sw_event(PERF_COUNT_SW_SPF, 1, regs, address); + goto done; + } + /* When running in the kernel we expect faults to occur only to * addresses in user space. All other faults represent errors in the * kernel and should generate an OOPS. Unfortunately, in the case of an @@ -565,6 +580,7 @@ static int __do_page_fault(struct pt_regs *regs, unsigned long address, up_read(¤t->mm->mmap_sem); +done: if (unlikely(fault & VM_FAULT_ERROR)) return mm_fault_error(regs, address, fault); -- 2.7.4