From patchwork Thu Nov 25 01:28:32 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sean Christopherson X-Patchwork-Id: 12638319 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0956FC433F5 for ; Thu, 25 Nov 2021 01:58:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1353228AbhKYCBW (ORCPT ); Wed, 24 Nov 2021 21:01:22 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34350 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229700AbhKYB7S (ORCPT ); Wed, 24 Nov 2021 20:59:18 -0500 Received: from mail-pf1-x449.google.com (mail-pf1-x449.google.com [IPv6:2607:f8b0:4864:20::449]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D7DF8C061191 for ; Wed, 24 Nov 2021 17:29:23 -0800 (PST) Received: by mail-pf1-x449.google.com with SMTP id m16-20020a628c10000000b004a282d715b2so2543139pfd.11 for ; Wed, 24 Nov 2021 17:29:23 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=reply-to:date:in-reply-to:message-id:mime-version:references :subject:from:to:cc; bh=1xAVDlHQKzkM70YKCpZg/NA4ILHPMzItk81iCtJ9oUY=; b=jRSj3dOTg7ibZaKnNap9/nuXfrU1FNeW8W5m2ekZ+uQFNaVW2Zz20kwJ9ASTKE7MAA d9hOc95cgM5rFNeDqE/PmaJHnDv8OPsNe/TzBvu6htMd/gbIHO5hpw9Ovx3sik1m8p2N /3eemmE9s5HltdOmec7SDCtMY/X+BV8aXQAc3reVRS+9e3ih4t1hwkGcKHvrXZLsJir6 U7jQn7DRWlvIqX0oHOr8e/eojwUgyqGOn0+QYdE2K9EgzVvpm7FTsifqSNst84mnsUCD pjLC/SdXxhMRoej7a8GWFFEVuoZelnGOj3n4LLbj9QwrISaoWkfqn4uAoAo8m0VqWjR5 XROA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:reply-to:date:in-reply-to:message-id :mime-version:references:subject:from:to:cc; bh=1xAVDlHQKzkM70YKCpZg/NA4ILHPMzItk81iCtJ9oUY=; b=BrncJfiQjIBh7mcHWyCwRnrT8Sl2Lrmv9sU5bxYU2BfbzUfIbqJihRNs+mJV2X2X6e qNzj4M22oUKC7/7c783CCv4ML38mT2UsF3CpzhIJahq7fQ5l6neV5+7FRlfyKfSr7FOD 9erj/7Io8XAYAVZ6Pzopgb4YJBe3M/9ipJh58ly/aOU/NkEnAjR9ZF7NK+DhbUEJipoU hGkZe4ZQOzHODCekX9Lua/JE5jktzl0nVThJtP9nypzo3NXFQjXabyVUdKm+NIDpQM0u FhzaFZluvSrWDdjuUIIa20yIvnbHWpDTsJPwX/HebaHixXOiXUCg4blojmi6taVbo0n8 5RJA== X-Gm-Message-State: AOAM531GI/LFHo84HHbvLLK4YZjt/OAsPGZJ6t0hjuRIYeIvjCsnXxCX Smdmo5uVwdDGBmetBCHzVbcuZO4L1Ho= X-Google-Smtp-Source: ABdhPJxse+1o3kKO0U2lh/rTp3faQ5qNFAIxemcqX7T6zlleejC/u3tu1KJTXWozPTyGZ1EnZuA4d+wvSUY= X-Received: from seanjc.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:3e5]) (user=seanjc job=sendgmr) by 2002:a17:902:bb97:b0:144:d5cb:969f with SMTP id m23-20020a170902bb9700b00144d5cb969fmr25118167pls.36.1637803763417; Wed, 24 Nov 2021 17:29:23 -0800 (PST) Reply-To: Sean Christopherson Date: Thu, 25 Nov 2021 01:28:32 +0000 In-Reply-To: <20211125012857.508243-1-seanjc@google.com> Message-Id: <20211125012857.508243-15-seanjc@google.com> Mime-Version: 1.0 References: <20211125012857.508243-1-seanjc@google.com> X-Mailer: git-send-email 2.34.0.rc2.393.gf8c9666880-goog Subject: [kvm-unit-tests PATCH 14/39] x86/access: Don't write page tables if desired PTE is same as current PTE From: Sean Christopherson To: Paolo Bonzini Cc: kvm@vger.kernel.org, Sean Christopherson Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Avoid spurious PTE writes, KVM doesn't check if old==new when handling write-protected SPTEs and triggers an MMU sync when using shadow paging even if the SPTE is unchanged. Signed-off-by: Sean Christopherson --- x86/access.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/x86/access.c b/x86/access.c index abc6590..53b1221 100644 --- a/x86/access.c +++ b/x86/access.c @@ -704,7 +704,8 @@ static void __ac_setup_specific_pages(ac_test_t *at, u64 pd_page, u64 pt_page) assert(0); } - *ptep = pte; + if (pte != *ptep) + *ptep = pte; parent_pte = pte; }