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=-17.4 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT, USER_IN_DEF_DKIM_WL 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 63B15C32771 for ; Thu, 16 Jan 2020 00:16:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3622422522 for ; Thu, 16 Jan 2020 00:16:56 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="tOuQX0ex" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730090AbgAPAQz (ORCPT ); Wed, 15 Jan 2020 19:16:55 -0500 Received: from mail-pl1-f201.google.com ([209.85.214.201]:46722 "EHLO mail-pl1-f201.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726310AbgAPAQz (ORCPT ); Wed, 15 Jan 2020 19:16:55 -0500 Received: by mail-pl1-f201.google.com with SMTP id t17so7771731plr.13 for ; Wed, 15 Jan 2020 16:16:54 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:message-id:mime-version:subject:from:to:cc; bh=t5hhiMVaGy2q0E/z2T4ycE665LCZYtF+TTm8Tr1smIg=; b=tOuQX0exFrlUtIawNreCUMl5ovbrJjoQ387lqvKrIjWgH/iE3VZ0K1ng2Ksq2hNC0I ltp2RJULwVsQphki50fmjuWZYJ2gkb8tSuzWo+JwVXO3QVj5m+9oRgVbOtj6mZNgrIO0 jK1jP88lWKP9T+kBzi3Bg2f11tvTTrFor6fNSwnvGc9hIxdP/0J0hEElDvUtVZT94gf+ QCC0CykWQ7KjG5VzJDAD/YAD4KjRalEs1jkLh4w3EMgt92QtYM3urk7tp+Qbu2Yau8Gl uPshjpFpIc5Fsv4kmFFLnVHWr/qmKu5M6EYnNK9hNGu3lXQ0LZuGWfJ7oEfIp6wCrr/2 eOcA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:message-id:mime-version:subject:from:to:cc; bh=t5hhiMVaGy2q0E/z2T4ycE665LCZYtF+TTm8Tr1smIg=; b=snh5QPevCxDM8Wql63REZJ7yZzQhp+6ig1TD9bfvXw/6NE8zRNTKW3DACjtuomoYsa F5qHKxH57rwxX04LEkPg3Mk2+M+fzVQY49PToxig/aBCcsKvTsVq/81CiGGMC9vKt5IU P3NzeOs4FVmFleyo4PpG6ezz4uucuFESbn3YDuqzzyii2kf5ESIggx+oHAuW/ToonFPO e9GGE07xPkXktbwLF7bz2nIwUi9+AV5wIclXqaBPfkIdBUfWAw/KK33mFZrL7X4ftPKm FilB6rOP60HK776spS5i9ZdFN8YmoUsf9H6bG1/mw7uFV7pGsowCS3C+qeRkuHajl2kZ +r0g== X-Gm-Message-State: APjAAAUDRv5RL4WbjUYH4kTYGd85fmE6Xxk8y/4LHsHr2ehStcFzGU8C t4USiXDVN3grLPUh4Ea2zYILvq1KXZ5he3E0EjBbXt/CLE1+Q4fKnjZaz3G+B+m6cGdluTB81dt P8ox2UbMzwr+neoe81AZq0YyepWH1e+Z+ptaW699LzrU9XvKNkbSCsb8kdG0iqsQ= X-Google-Smtp-Source: APXvYqzYOrXmkuotXUi1BcXQtiDrkmbf0DY4rTwfJCnnNJ/jNSYeIZwrPXL3Jgyqs+kgCMk87xe9KNpGynZknQ== X-Received: by 2002:a65:5608:: with SMTP id l8mr36747108pgs.210.1579133814000; Wed, 15 Jan 2020 16:16:54 -0800 (PST) Date: Wed, 15 Jan 2020 16:16:35 -0800 Message-Id: <20200116001635.174948-1-jmattson@google.com> Mime-Version: 1.0 X-Mailer: git-send-email 2.25.0.rc1.283.g88dfdc4193-goog Subject: [PATCH] kvm: x86: Don't dirty guest memory on every vcpu_put() From: Jim Mattson To: kvm@vger.kernel.org, Paolo Bonzini Cc: Jim Mattson , Kevin Mcgaire , Ben Gardon , Oliver Upton Content-Type: text/plain; charset="UTF-8" Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Beginning with commit 0b9f6c4615c99 ("x86/kvm: Support the vCPU preemption check"), the KVM_VCPU_PREEMPTED flag is set in the guest copy of the kvm_steal_time struct on every call to vcpu_put(). As a result, guest memory is dirtied on every call to vcpu_put(), even when the VM is quiescent. To avoid dirtying guest memory unnecessarily, don't bother setting the flag in the guest copy of the struct if it is already set in the kernel copy of the struct. If a different vCPU thread clears the guest copy of the flag, it will no longer get reset on the next call to vcpu_put, but it's not clear that resetting the flag in this case was intentional to begin with. Signed-off-by: Jim Mattson Tested-by: Kevin Mcgaire Reviewed-by: Ben Gardon Reviewed-by: Oliver Upton --- arch/x86/kvm/x86.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index cf917139de6b..3dc17b173f88 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -3504,6 +3504,9 @@ static void kvm_steal_time_set_preempted(struct kvm_vcpu *vcpu) if (!(vcpu->arch.st.msr_val & KVM_MSR_ENABLED)) return; + if (vcpu->arch.st.steal.preempted & KVM_VCPU_PREEMPTED) + return; + vcpu->arch.st.steal.preempted = KVM_VCPU_PREEMPTED; kvm_write_guest_offset_cached(vcpu->kvm, &vcpu->arch.st.stime, -- 2.25.0.rc1.283.g88dfdc4193-goog