From patchwork Wed May 3 10:52:23 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Xiao Guangrong X-Patchwork-Id: 9709367 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id A5ACA60351 for ; Wed, 3 May 2017 10:54:09 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 984E528427 for ; Wed, 3 May 2017 10:54:09 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 8B932285E9; Wed, 3 May 2017 10:54:09 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.5 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, FREEMAIL_FROM, RCVD_IN_DNSWL_HI, RCVD_IN_SORBS_SPAM autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 0368728427 for ; Wed, 3 May 2017 10:54:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754081AbdECKyG (ORCPT ); Wed, 3 May 2017 06:54:06 -0400 Received: from mail-pf0-f195.google.com ([209.85.192.195]:33163 "EHLO mail-pf0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753544AbdECKxW (ORCPT ); Wed, 3 May 2017 06:53:22 -0400 Received: by mail-pf0-f195.google.com with SMTP id b23so3810136pfc.0; Wed, 03 May 2017 03:53:22 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references; bh=EH9FunFGlPGrNrIprECc6/Uz6FUMYrEnCUgHJKW+Ggc=; b=rV8cK4oA4caxll7s4shrfOcIHu/l4MdbxUOmPe7FEsSzOva4GFBK2ckoiNjNpXy1Mb h0uRFR8VsmiC7UoC5MxyAMPl1IH5IeNE+ZcaCmlb8bxExD53MCX24Izaaq3KF7jl0wfF kv6tkr6AtgkQW//qP0uzfAogEcsOzSEAFs4TPAToJJfJhnGT8/36d//avU0nqXTSYni9 vWkwK91b92REJ+mO7ICVEZKtnyjHFeucroDf0C+QJa/jtyns3ejBp546GOYR02vLxKXG AHwoyCtUUR+Sn74E4sUxTEksYDW2CrK11I4av+4R5aoey6itrQkyKpoE84zp2rvkHzuO UXbw== 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:in-reply-to :references; bh=EH9FunFGlPGrNrIprECc6/Uz6FUMYrEnCUgHJKW+Ggc=; b=HAALYv0zNFem6A6laZCpQBPdTsCtuLqO4xLtzuA4VB+PIGuwy7+PJiQzybUoI407E/ iFxXHMjFtRybiFCQyjonAJxVYL9gMmgvm7rmX9ysVNQZqTVBPkSryCVHKCU2DkbNpvDg 2FO37/7RrMUG/pR9riTbvQDO8CykLSTFoSV2jnKwbfX6nF6siUr22t0BDjK7SqDIOsQl nq1zQxRgi19FAjvKIcUvoJNfmf0dpmYaaQRZlLnG4CZAwskP0z+CRy5hdb8wtFCAbaTM /YUwWyw+IkNGIONRWH0GCRELjWCxr7n1SFab2qjc9f6dW7WCS4Rwh5rzXhg2NBb22EPI eY6w== X-Gm-Message-State: AN3rC/4zxSFPeK/4KykSDFmtTApb8N+agdVgc+wRcNlCpu6iX6/GwQk3 4OKpXtYYPWj0Dx/A X-Received: by 10.84.232.204 with SMTP id x12mr14429850plm.77.1493808801778; Wed, 03 May 2017 03:53:21 -0700 (PDT) Received: from eric.tencent.com ([203.205.141.35]) by smtp.gmail.com with ESMTPSA id d24sm4395561pfb.97.2017.05.03.03.53.18 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 03 May 2017 03:53:21 -0700 (PDT) From: guangrong.xiao@gmail.com X-Google-Original-From: xiaoguangrong@tencent.com To: pbonzini@redhat.com, mtosatti@redhat.com, avi.kivity@gmail.com, rkrcmar@redhat.com Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, qemu-devel@nongnu.org, Xiao Guangrong Subject: [PATCH 6/7] KVM: MMU: clarify fast_pf_fix_direct_spte Date: Wed, 3 May 2017 18:52:23 +0800 Message-Id: <20170503105224.19049-7-xiaoguangrong@tencent.com> X-Mailer: git-send-email 2.9.3 In-Reply-To: <20170503105224.19049-1-xiaoguangrong@tencent.com> References: <20170503105224.19049-1-xiaoguangrong@tencent.com> Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP From: Xiao Guangrong The writable spte can not be locklessly fixed and add a WARN_ON() to trigger the warning if something out of our mind happens, that is good for us to track if the log for writable spte is missed on the fast path Signed-off-by: Xiao Guangrong --- arch/x86/kvm/mmu.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c index ad6ee46..f6a74e7 100644 --- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -3225,6 +3225,15 @@ fast_pf_fix_direct_spte(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp, WARN_ON(!sp->role.direct); /* + * the original spte can not be writable as only the spte which + * fulfills is_access_track_spte() or + * spte_can_locklessly_be_made_writable() can be locklessly fixed, + * for the former, the W bit is always cleared, for the latter, + * there is nothing to do if it is already writable. + */ + WARN_ON(is_writable_pte(old_spte)); + + /* * Theoretically we could also set dirty bit (and flush TLB) here in * order to eliminate unnecessary PML logging. See comments in * set_spte. But fast_page_fault is very unlikely to happen with PML @@ -3239,7 +3248,7 @@ fast_pf_fix_direct_spte(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp, if (cmpxchg64(sptep, old_spte, new_spte) != old_spte) return false; - if (is_writable_pte(new_spte) && !is_writable_pte(old_spte)) { + if (is_writable_pte(new_spte)) { /* * The gfn of direct spte is stable since it is * calculated by sp->gfn.