From mboxrd@z Thu Jan 1 00:00:00 1970 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=-18.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,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 15212C433B4 for ; Fri, 30 Apr 2021 19:54:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E70036147D for ; Fri, 30 Apr 2021 19:54:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232400AbhD3Tyv (ORCPT ); Fri, 30 Apr 2021 15:54:51 -0400 Received: from server.lespinasse.org ([63.205.204.226]:60163 "EHLO server.lespinasse.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232428AbhD3Txg (ORCPT ); Fri, 30 Apr 2021 15:53:36 -0400 DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=lespinasse.org; i=@lespinasse.org; q=dns/txt; s=srv-14-ed; t=1619812353; h=from : to : cc : subject : date : message-id : in-reply-to : references : mime-version : content-transfer-encoding : from; bh=6izgSjuxJC/sQuVYlPY55kmOkeAgaUYZ6vcRO71jz20=; b=6MkGLKvM/4VtjyiymcFk2dABknx20mqKn0lGnp7hMFyHV9yFVB5srF0QXxkBHbz+uWWsP ZNa4wxs6B3JQuVwDg== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=lespinasse.org; i=@lespinasse.org; q=dns/txt; s=srv-14-rsa; t=1619812353; h=from : to : cc : subject : date : message-id : in-reply-to : references : mime-version : content-transfer-encoding : from; bh=6izgSjuxJC/sQuVYlPY55kmOkeAgaUYZ6vcRO71jz20=; b=A01bdPoVLNR+cYeuMSIDL5MvLvHSWzUFdNnBnPCOojMiIGawDh+laCnZlI26QdeJgQ2d7 HtJ8ez8EsInqYn47P5AqrtvW44W2A4iaJ+DXOm4cyjpK1gHE1ei9ThzshowQotc/PYU71GR NWtJNkcpJEYKx0QA9/204+L3r8e07/58DiEs56YhlJrr6RGoN6/EGStz6dOvMYGS1SaTjGj JkP/bRYRI6D/AyQCI+ZvWaOz/Snj3vfs9GJgyUEh3uA/9KfMI0l7ulaFCwoqbHCnxX4TJtK 4LOh2CSRTHTUxH1RfGFRbGOVN0+ndlqMVNKzGdVxrUVbX4nlsb6k6JOl3l0g== Received: from zeus.lespinasse.org (zeus.lespinasse.org [IPv6:fd00::150:0]) by server.lespinasse.org (Postfix) with ESMTPS id 9E4B616035C; Fri, 30 Apr 2021 12:52:33 -0700 (PDT) Received: by zeus.lespinasse.org (Postfix, from userid 1000) id 8ED4019F521; Fri, 30 Apr 2021 12:52:33 -0700 (PDT) From: Michel Lespinasse To: Linux-MM , Linux-Kernel Cc: Laurent Dufour , Peter Zijlstra , Michal Hocko , Matthew Wilcox , Rik van Riel , Paul McKenney , Andrew Morton , Suren Baghdasaryan , Joel Fernandes , Andy Lutomirski , Michel Lespinasse Subject: [PATCH 22/29] mm: implement and enable speculative fault handling in handle_pte_fault() Date: Fri, 30 Apr 2021 12:52:23 -0700 Message-Id: <20210430195232.30491-23-michel@lespinasse.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20210430195232.30491-1-michel@lespinasse.org> References: <20210430195232.30491-1-michel@lespinasse.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 cb66585f5145..c3cd29d3acc6 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -3120,6 +3120,7 @@ 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; @@ -3140,6 +3141,8 @@ 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) { @@ -3193,6 +3196,8 @@ 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); } @@ -4383,13 +4388,8 @@ 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); -- 2.20.1