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 8F570377A9A; Tue, 28 Jul 2026 00:36:14 +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=1785198976; cv=none; b=oaDi2pO3Z6T4pU3X7N65/dPB7ww5MuofW3Ehs2XuitJMY/KXqAYkzbneZCRZeVN2pJnRdwTK3Z4tQD7cdbti/dMoOmiC06tdwiu/RtBIxFRJtySAcX/HGc1oSmqjJYE8+hdH5Lu0KlzBUsyVB3zX9WJkXWiaOdn/yA69b1yLJ2k= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785198976; c=relaxed/simple; bh=MCvFU56yZVnCOxBbY6mTcY3sDioQwxYX+DhC8atP05Y=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=V6unqoK8HkCSHjqHvFXlOX2Cer88ReuDs+FtuRqyZlSkAJzChRFnhJWnerKtm+SW492zrKOW0Vi9Gpam+DzECAIpetek8jUIT2LkRYIGfOT/pDUSO2LblAozmgtvap8Wf2PVpmYdgZs4mx4q5G9FhVoe5mk5exmCYKyNbWsxEcE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=dlP/1w1A; 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="dlP/1w1A" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 276691F00A3D; Tue, 28 Jul 2026 00:36:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1785198974; bh=h2Ysdj0qK8DvRim1C1PzxOxEX/Ksc8yb+shMuBLswnw=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=dlP/1w1AjBRsjEkEdPJCmBqKJCWNaibaykBSJPrSFJV6ek2Vg0O/cTeaUpDoCquEq L89L5hFZAsaBIHi7oCYgjutAhRjyztSvSuQ/p+xEoYefot/K0RjPYXaLGwYSndnfVl IpakIsf33N+PY/8v5vr+2okvs5qi9/iYhXBmAbZBz731UEOOoO05gaVlekYVN6FZBo V3KB6khSp77PnfLdlnvK8TSzxfUrJFCB1cRG1JNPaGhsM5CAj+bFCC/uAWx3UfIB4J WexL0RTJMk64KPmMb2xXEtxIMniQkaqDTEvwh9igRuq13ES6eUmF/bjbIH1rd1qtAf GktMFhBLI14qw== 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 v1 22/28] KVM: nSVM: Do not reset TLB_CONTROL in vmcb02 on nested VM-Enter Date: Tue, 28 Jul 2026 00:35:51 +0000 Message-ID: <20260728003557.1136583-23-yosry@kernel.org> X-Mailer: git-send-email 2.55.0.229.g6434b31f56-goog In-Reply-To: <20260728003557.1136583-1-yosry@kernel.org> References: <20260728003557.1136583-1-yosry@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@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 undos 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 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 f50e21fd363fc..58e7d099c559e 100644 --- a/arch/x86/kvm/svm/nested.c +++ b/arch/x86/kvm/svm/nested.c @@ -719,12 +719,7 @@ 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); } @@ -966,9 +961,6 @@ 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; -- 2.55.0.229.g6434b31f56-goog