From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qk0-f197.google.com (mail-qk0-f197.google.com [209.85.220.197]) by kanga.kvack.org (Postfix) with ESMTP id F3ACA6B04C8 for ; Thu, 17 May 2018 07:07:47 -0400 (EDT) Received: by mail-qk0-f197.google.com with SMTP id p190-v6so3551514qkc.17 for ; Thu, 17 May 2018 04:07:47 -0700 (PDT) Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com. [148.163.156.1]) by mx.google.com with ESMTPS id r126-v6si360546qke.293.2018.05.17.04.07.46 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 17 May 2018 04:07:47 -0700 (PDT) Received: from pps.filterd (m0098393.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.22/8.16.0.22) with SMTP id w4HB4BAE022824 for ; Thu, 17 May 2018 07:07:46 -0400 Received: from e06smtp15.uk.ibm.com (e06smtp15.uk.ibm.com [195.75.94.111]) by mx0a-001b2d01.pphosted.com with ESMTP id 2j187ph2tj-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Thu, 17 May 2018 07:07:46 -0400 Received: from localhost by e06smtp15.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Thu, 17 May 2018 12:07:42 +0100 From: Laurent Dufour Subject: [PATCH v11 25/26] powerpc/mm: add speculative page fault Date: Thu, 17 May 2018 13:06:32 +0200 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> Message-Id: <1526555193-7242-26-git-send-email-ldufour@linux.vnet.ibm.com> Sender: owner-linux-mm@kvack.org List-ID: 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 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