From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 619BA22A4F1; Thu, 8 Oct 2026 00:14:50 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791418491; cv=none; b=qzufIXPT2CaD+g0+X6CTIueEyCtH/6kw0WzKO3s2pDTgT7zhcAYB3YkBA/ay/Es+ZknMs2ptbN+VZwuon17aU1SafzW0mi/jCAdTq1pCifp0plIETQFlxXMktSD0epvGLXMRvw/Klizdu/lRAcLfWhKegQTcWd9W0Vg5ebN4dYc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791418491; c=relaxed/simple; bh=E/4UGOWRSWf7isWli2GFSoCTNA6LhGE8C9TXrVyleZY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=AjEN4vzz5CcSC7YrlAoa6cyP00O9EP7mBKV/1fX+iPWOCG65SB23eHpHXSO77tbf1WQ5pFB+ZJ3DU38PH1fnkBRK8sLilSDVhGEPlF0PXTD4E+n1rV1wFOwu5euXDloibD1LNZqggEYjXr1zic+W6sMPzJjxZng1r5iTcepJuJg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=DqYDeo4R; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="DqYDeo4R" Received: by smtp.kernel.org (Postfix) with ESMTPSA id EEBF01F000FF; Thu, 8 Oct 2026 00:14:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1791418490; bh=D/JrpwuTbYo1fodgS69GXDrk/zksLYIOyr4jJVnNBgg=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=DqYDeo4R0+V2fMSZs2kO5p5pXc4OwGRb/HpjTvKS5xirNviScH9PQ/sx5tTuwNbhE GBJMUqz6phZlOaKnlZ0XPV/HMe59f89gMOW04r85SkTAf8cSejRDVapWxXV2tHtWkg TzjQZnguO9t6nofQrr9e6w+Cm2mbw3hGloY53SpScOGBAbpMy3np2hIXpe3v7MYwim RHMjMWvOV419Rxz4bnKpuF27wEWh13dsGDDdKGYbZRpRRTYMwj+KHRoeY86JzRcE9V jlwVu4qdsUlndRxkSPt++r8JfWVsPBTu/RH7EUyfZ0o/phAkk0XH7jAxYN46HFDlyT 9lHte6YUOK4Og== From: Yosry Ahmed To: Sean Christopherson Cc: Paolo Bonzini , Jim Mattson , Maxim Levitsky , Vitaly Kuznetsov , Tom Lendacky , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Yosry Ahmed Subject: [PATCH v2 23/29] KVM: nSVM: Do not reset TLB_CONTROL in vmcb02 on nested VM-Enter Date: Thu, 8 Oct 2026 00:14:19 +0000 Message-ID: <20261008001425.2458927-24-yosry@kernel.org> X-Mailer: git-send-email 2.56.0.360.g66cac248cb-goog In-Reply-To: <20261008001425.2458927-1-yosry@kernel.org> References: <20261008001425.2458927-1-yosry@kernel.org> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Stop clearing TLB_CONTROL when preparing the control area of vmcb02, as this potentially undoes pending TLB flushes for L2 (e.g. through KVM_REQ_TLB_FLUSH while L1 is running), and remove the associated TODO comment. This is currently harmless, because nested_svm_entry_tlb_flush() always requests KVM_REQ_TLB_FLUSH_CURRENT on nested VM-Enter, which sets TLB_CONTROL again before L2 is actually run. However, always flushing will soon go away with proper TLB handling for L2, at which point always clearing TLB_CONTROL would be a bug. Clearing TLB_CONTROL on nested VM-Enter was probably done because TLB_CONTROL is not cleared by the CPU on VM-Exit. However, KVM always clears TLB_CONTROL in the active VMCB after a successful VMRUN. Hence, at nested VM-Enter, TLB_CONTROL in vmcb02 can only be non-zero if a TLB flush is queued for L2 while L1 is running (i.e. KVM_REQ_TLB_FLUSH), and that should never be ignored. Signed-off-by: Yosry Ahmed --- arch/x86/kvm/svm/nested.c | 10 +--------- 1 file changed, 1 insertion(+), 9 deletions(-) diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c index 8e4686b0d603a..738ec1f2ec869 100644 --- a/arch/x86/kvm/svm/nested.c +++ b/arch/x86/kvm/svm/nested.c @@ -723,12 +723,7 @@ static void nested_svm_entry_tlb_flush(struct kvm_vcpu *vcpu) kvm_make_request(KVM_REQ_TLB_FLUSH_GUEST, vcpu); } - /* - * TODO: optimize unconditional TLB flush/MMU sync. A partial list of - * things to fix before this can be conditional: - * - * - Don't crush a pending TLB flush in vmcb02 on nested VMRUN - */ + /* TODO: optimize unconditional TLB flush/MMU sync */ kvm_make_request(KVM_REQ_MMU_SYNC, vcpu); kvm_make_request(KVM_REQ_TLB_FLUSH_CURRENT, vcpu); } @@ -975,9 +970,6 @@ static void nested_vmcb02_prepare_control(struct vcpu_svm *svm) vmcb02->control.asid = svm->nested.asid02; - /* Overwritten later if necessary. */ - vmcb_clr_flush_asid(vmcb02); - /* Use vmcb01 MMU and format if guest does not use nNPT */ if (nested_npt_enabled(svm)) { vmcb02->control.misc_ctl &= ~SVM_MISC_ENABLE_GMET; -- 2.56.0.360.g66cac248cb-goog