From patchwork Wed Apr 7 01:44:45 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Michel Lespinasse X-Patchwork-Id: 12186459 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-16.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id F38B3C433B4 for ; Wed, 7 Apr 2021 01:45:43 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id A4FA361165 for ; Wed, 7 Apr 2021 01:45:43 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A4FA361165 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=lespinasse.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 633F58E0015; Tue, 6 Apr 2021 21:45:10 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id E141C8E0008; Tue, 6 Apr 2021 21:45:09 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 36B948E0008; Tue, 6 Apr 2021 21:45:09 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0201.hostedemail.com [216.40.44.201]) by kanga.kvack.org (Postfix) with ESMTP id 647E86B0092 for ; Tue, 6 Apr 2021 21:45:08 -0400 (EDT) Received: from smtpin34.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 2B3AB81CF for ; Wed, 7 Apr 2021 01:45:08 +0000 (UTC) X-FDA: 78003877896.34.8E25F41 Received: from server.lespinasse.org (server.lespinasse.org [63.205.204.226]) by imf23.hostedemail.com (Postfix) with ESMTP id 9B25EA000395 for ; Wed, 7 Apr 2021 01:45:06 +0000 (UTC) DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=lespinasse.org; i=@lespinasse.org; q=dns/txt; s=srv-11-ed; t=1617759902; h=from : to : cc : subject : date : message-id : in-reply-to : references : mime-version : content-transfer-encoding : from; bh=amUPmRB3lhaJkohzuLZ4RtQ8DU3T54MYn5RloG5fdOk=; b=z2Fs4Sr8tgnyNRxzBI/Qpcy1P6DLuAkRsEWkyC+RTtb0wEJIEd05hnB2MY0kNtj3w4TPx izNmbCPXX4Oli6tCQ== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=lespinasse.org; i=@lespinasse.org; q=dns/txt; s=srv-11-rsa; t=1617759902; h=from : to : cc : subject : date : message-id : in-reply-to : references : mime-version : content-transfer-encoding : from; bh=amUPmRB3lhaJkohzuLZ4RtQ8DU3T54MYn5RloG5fdOk=; b=STR1621+RtKTEUrfNGZuKFxncsNgsYjBbFmP0TY1i7nINnGvGd8RC7HxYZylM4TwF9ipc 2lJKhgHBNzrI/mmtaYhir2hDOmgFM0uMh2+9qOId0KEXhtaP/BYpzV/1c0420if3gvpykh2 q9FoAdafWcOOGwVE6Llm1KbgxG63CwFM3Dzf4b3fB8u3iUZNPLvGVlYBu29QFKF+igMX3bv Lcnb2SWEBQKu+0iLdI9bRaoQ7UYa4nEnI6AiUFRWpcLtXmiHhcmXP4x+Bk+ezGFAp4Q11Zt ehgmwHil39XlGZvKvXYkBiSkRNfP8THZyYuG9Y/SJYaePQGz3RwdeWVRGYlw== Received: from zeus.lespinasse.org (zeus.lespinasse.org [10.0.0.150]) by server.lespinasse.org (Postfix) with ESMTPS id EF7E4160330; Tue, 6 Apr 2021 18:45:02 -0700 (PDT) Received: by zeus.lespinasse.org (Postfix, from userid 1000) id E0F2F19F31E; Tue, 6 Apr 2021 18:45:02 -0700 (PDT) From: Michel Lespinasse To: Linux-MM Cc: Laurent Dufour , Peter Zijlstra , Michal Hocko , Matthew Wilcox , Rik van Riel , Paul McKenney , Andrew Morton , Suren Baghdasaryan , Joel Fernandes , Rom Lemarchand , Linux-Kernel , Michel Lespinasse Subject: [RFC PATCH 20/37] mm: implement and enable speculative fault handling in handle_pte_fault() Date: Tue, 6 Apr 2021 18:44:45 -0700 Message-Id: <20210407014502.24091-21-michel@lespinasse.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20210407014502.24091-1-michel@lespinasse.org> References: <20210407014502.24091-1-michel@lespinasse.org> MIME-Version: 1.0 X-Rspamd-Queue-Id: 9B25EA000395 X-Stat-Signature: py4gt3gzbqdqfewtjcjjazfht6mqsyer X-Rspamd-Server: rspam02 Received-SPF: none (lespinasse.org>: No applicable sender policy available) receiver=imf23; identity=mailfrom; envelope-from=""; helo=server.lespinasse.org; client-ip=63.205.204.226 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1617759906-13611 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: In handle_pte_fault(), allow speculative execution to proceed. Use pte_spinlock() to validate the mmap sequence count when locking the page table. If speculative execution proceeds through do_wp_page(), ensure that we end up in the wp_page_reuse() or wp_page_copy() paths, rather than wp_pfn_shared() or wp_page_shared() (both unreachable as we only handle anon vmas so far) or handle_userfault() (needs an explicit abort to handle non-speculatively). Signed-off-by: Michel Lespinasse --- mm/memory.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/mm/memory.c b/mm/memory.c index 547d9d0ee962..fc555fae0844 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -3103,6 +3103,7 @@ static vm_fault_t wp_pfn_shared(struct vm_fault *vmf) { struct vm_area_struct *vma = vmf->vma; + VM_BUG_ON(vmf->flags & FAULT_FLAG_SPECULATIVE); if (vma->vm_ops && vma->vm_ops->pfn_mkwrite) { vm_fault_t ret; @@ -3123,6 +3124,8 @@ static vm_fault_t wp_page_shared(struct vm_fault *vmf) struct vm_area_struct *vma = vmf->vma; vm_fault_t ret = VM_FAULT_WRITE; + VM_BUG_ON(vmf->flags & FAULT_FLAG_SPECULATIVE); + get_page(vmf->page); if (vma->vm_ops && vma->vm_ops->page_mkwrite) { @@ -3176,6 +3179,8 @@ static vm_fault_t do_wp_page(struct vm_fault *vmf) if (userfaultfd_pte_wp(vma, *vmf->pte)) { pte_unmap_unlock(vmf->pte, vmf->ptl); + if (vmf->flags & FAULT_FLAG_SPECULATIVE) + return VM_FAULT_RETRY; return handle_userfault(vmf, VM_UFFD_WP); } @@ -4366,13 +4371,8 @@ static vm_fault_t handle_pte_fault(struct vm_fault *vmf) if (pte_protnone(vmf->orig_pte) && vma_is_accessible(vmf->vma)) return do_numa_page(vmf); - if (vmf->flags & FAULT_FLAG_SPECULATIVE) { - pte_unmap(vmf->pte); + if (!pte_spinlock(vmf)) return VM_FAULT_RETRY; - } - - vmf->ptl = pte_lockptr(vmf->vma->vm_mm, vmf->pmd); - spin_lock(vmf->ptl); entry = vmf->orig_pte; if (unlikely(!pte_same(*vmf->pte, entry))) { update_mmu_tlb(vmf->vma, vmf->address, vmf->pte);