From patchwork Tue Jun 20 09:15:25 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Xiao Guangrong X-Patchwork-Id: 9798915 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 147BF601BC for ; Tue, 20 Jun 2017 09:17:08 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 0BF322810E for ; Tue, 20 Jun 2017 09:17:08 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 00A7C2847C; Tue, 20 Jun 2017 09:17:07 +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=-7.0 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, FREEMAIL_FROM, RCVD_IN_DNSWL_HI autolearn=unavailable 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 A8D332810E for ; Tue, 20 Jun 2017 09:17:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752996AbdFTJQq (ORCPT ); Tue, 20 Jun 2017 05:16:46 -0400 Received: from mail-pf0-f193.google.com ([209.85.192.193]:33122 "EHLO mail-pf0-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751989AbdFTJP7 (ORCPT ); Tue, 20 Jun 2017 05:15:59 -0400 Received: by mail-pf0-f193.google.com with SMTP id w12so21607104pfk.0; Tue, 20 Jun 2017 02:15:59 -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=DaNO5Ln0PEifPXwFkrDyQ2ovE8Tg5tNeAITmsZ8hO40=; b=XCzep5NGzXMSFNW5MW3OdJUrDfFRKLKoNeReGsM+fR0N9Os39VuBzTHyQ7IFD44fh1 lm06NRto+0nbeDpr/JRAZiKSUNyFPsmzX1E2s7WSitqTKjcGCyAEn3qNaMG3kTufCXaE SmgQZO0JRFB7H/btErz9/+llPhhAX9gdn9cSY/bd5rCJCkZms0x2u9c+t/8PmG2+QX64 Pr0LkF+eXTwtv/HdzPKzi7k0WZV7fOmDYv/FDjs6wge5UOrVoaWP/29cxRKye0YyXmTs xhOCZA3RjYronPlUn6dO9BaF8hHvl0Lj2Tsi3Zo4icR8RIdYegXHs4DaxVm0GhGe7w8O 8RWw== 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=DaNO5Ln0PEifPXwFkrDyQ2ovE8Tg5tNeAITmsZ8hO40=; b=t/r1RI0IDdJFPWojGTbT9mp2kOH8Kzavn1QmneOwKY0WbfFORClZaq11+8MVQ5M+bJ x5nCJZd3Y5snWsLAYpiemUb/KE4b4/SLYSIk/VA0qSpZ1W8XUDGbFj86hMiwe+tB+Z+S jsS2/q9ss0ovxddJPZ6clvJZLmPfRkpk0yrizSaheCc0wJXflhtz6sqDSJNPstykiEEK PSTXmWcoGx0QXctkF330XAaS+RfMDoefC/CCbq+4juKAJQelVNM3UXRne4kP24znq7XZ V+uJPyTjhNv4w6ZS97OW7DNszwkyyuKjnT0+d1OD99W91bLnWB2IaNmtbFgqkHQpbqyr G7jA== X-Gm-Message-State: AKS2vOzQjo+FiXXC5pG9831BQOCHOZhNNheUpE958gt05VpFSIprmdOR 8fMKqSAiDq2RYA== X-Received: by 10.84.229.78 with SMTP id d14mr13395841pln.212.1497950159170; Tue, 20 Jun 2017 02:15:59 -0700 (PDT) Received: from eric.tencent.com ([203.205.141.35]) by smtp.gmail.com with ESMTPSA id o12sm26343810pfi.9.2017.06.20.02.15.56 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 20 Jun 2017 02:15:58 -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 v2 6/7] KVM: MMU: clarify fast_pf_fix_direct_spte Date: Tue, 20 Jun 2017 17:15:25 +0800 Message-Id: <20170620091526.4287-7-xiaoguangrong@tencent.com> X-Mailer: git-send-email 2.9.4 In-Reply-To: <20170620091526.4287-1-xiaoguangrong@tencent.com> References: <20170620091526.4287-1-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 c011ab0..7711953 100644 --- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -3240,6 +3240,15 @@ 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 @@ -3254,7 +3263,7 @@ 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.