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=-2.6 required=3.0 tests=DATE_IN_PAST_06_12, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT autolearn=no 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 5463BC3A59E for ; Sat, 24 Aug 2019 06:13:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 29C1121670 for ; Sat, 24 Aug 2019 06:13:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726521AbfHXGNW (ORCPT ); Sat, 24 Aug 2019 02:13:22 -0400 Received: from mail-pf1-f193.google.com ([209.85.210.193]:43806 "EHLO mail-pf1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725948AbfHXGNW (ORCPT ); Sat, 24 Aug 2019 02:13:22 -0400 Received: by mail-pf1-f193.google.com with SMTP id v12so8052749pfn.10 for ; Fri, 23 Aug 2019 23:13:22 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id; bh=kSi1/f8j26P6m8VkHa3OU1uYHBFvYkufKJqChTfaGcc=; b=YP0wfvloC0RE4H8ukBubrZDuNyLFFAVVZhXIpAiwiYLlY1x75ZwBD40z9AZrPFV2H9 iyXtGRCxDmv2g4dcnk0QmO0t/WXZmWeisGz/lx6vrtG4kREdDwOWWoEBg0D1PBxTt/Y9 0Wee8tw+s5JAfFSlDC7QfCjIpmhCs8ShJQWntAke8Cd6A3pGmQANPz+Otg9TFYinPJxo UlkiebRBdD/GXWggxHIO9n95SypnP3fI8TcbkrK+OnTtVhUYyfgw0msSn4m+DWmUwarR OPUIEcQywiIYjXFkadiEMmg2dnlEZCh5ZwWDV6izmrdxf7vbm586sdH2lXcfZTin/55Z Jblw== X-Gm-Message-State: APjAAAXnHjJNrgCvj1Eu5p+LnkBHMYB7dbRfKMO1hCga15Fk4NIoI6GP qTi1tcU9f3C49q8rH+xD5gc= X-Google-Smtp-Source: APXvYqyzmotg29WlYT9pkXK9P9heCKncRbC/vqUX7XZvWupKAL1OcGsRxV+aRC0/tGr4G+kqHzuB+g== X-Received: by 2002:a63:f357:: with SMTP id t23mr7202481pgj.421.1566627201449; Fri, 23 Aug 2019 23:13:21 -0700 (PDT) Received: from sc2-haas01-esx0118.eng.vmware.com ([66.170.99.1]) by smtp.gmail.com with ESMTPSA id o9sm3691360pgv.19.2019.08.23.23.13.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 23 Aug 2019 23:13:20 -0700 (PDT) From: Nadav Amit To: Andy Lutomirski , Dave Hansen Cc: x86@kernel.org, linux-kernel@vger.kernel.org, Peter Zijlstra , Thomas Gleixner , Ingo Molnar , Nadav Amit Subject: [RFC PATCH v2 0/3] x86/mm/tlb: Defer TLB flushes with PTI Date: Fri, 23 Aug 2019 15:52:45 -0700 Message-Id: <20190823225248.15597-1-namit@vmware.com> X-Mailer: git-send-email 2.17.1 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org INVPCID is considerably slower than INVLPG of a single PTE, but it is currently used to flush PTEs in the user page-table when PTI is used. Instead, it is possible to defer TLB flushes until after the user page-tables are loaded. Preventing speculation over the TLB flushes should keep the whole thing safe. In some cases, deferring TLB flushes in such a way can result in more full TLB flushes, but arguably this behavior is oftentimes beneficial. These patches are based and evaluated on top of the concurrent TLB-flushes v4 patch-set. I will provide more results later, but it might be easier to look at the time an isolated TLB flush takes. These numbers are from skylake, showing the number of cycles that running madvise(DONTNEED) which results in local TLB flushes takes: n_pages concurrent +deferred-pti change ------- ---------- ------------- ------ 1 2119 1986 -6.7% 10 6791 5417 -20% Please let me know if I missed something that affects security or performance. [ Yes, I know there is another pending RFC for async TLB flushes, but I think it might be easier to merge this one first ] RFC v1 -> RFC v2: * Wrong patches were sent before Nadav Amit (3): x86/mm/tlb: Change __flush_tlb_one_user interface x86/mm/tlb: Defer PTI flushes x86/mm/tlb: Avoid deferring PTI flushes on shootdown arch/x86/entry/calling.h | 52 +++++++++++- arch/x86/include/asm/paravirt.h | 5 +- arch/x86/include/asm/paravirt_types.h | 3 +- arch/x86/include/asm/tlbflush.h | 55 +++++++----- arch/x86/kernel/asm-offsets.c | 3 + arch/x86/kernel/paravirt.c | 7 +- arch/x86/mm/tlb.c | 117 ++++++++++++++++++++++++-- arch/x86/xen/mmu_pv.c | 21 +++-- 8 files changed, 218 insertions(+), 45 deletions(-) -- 2.17.1