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 9C07A32B130; Tue, 16 Jun 2026 00:42:31 +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=1781570553; cv=none; b=cvx26c/5JqTwZIHkXmXeTSyR0bRJaGHlZy2m2pXi6DiCq+zhwbSQQKlEaz0bJJirz/JmoDWtLQsKzpmkolQ7GB61/hHvgn9WtnDMBGa2q+Mhql8OCUCH0Qaei3PNxz2y/PXeVmoD6aiZQS0QaFajSYk6cd5UPgK/GJdDyEpG7Kc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781570553; c=relaxed/simple; bh=be/i1k4y/PlQ+lWXqPkZOHE95nazfIidNXtMiF8Z+oU=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=VHNuGeYvgSm6z6EtYhtyDYLcD3F0XBVGQKBKSC2z5uvHn4XwByaZPv3MU4eTe0j/JY2lYDMF3snXF2UD/G8oMv1o+enP+UiNJp1LTfp1CvaST1em6oJrnVQ19SoNiPUDc6Uw76NhzKYZcZ3biSKpQ0AXa87WgbfgpViI9Aydyss= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=j9HmOXgp; 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="j9HmOXgp" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 31EA51F00A3F; Tue, 16 Jun 2026 00:42:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1781570551; bh=nsZ3gkwmujzISH0RoBFsE/5KYiuBrdwVW09/X/kWErc=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=j9HmOXgpHfaUgI9YJz0dfcEO8HjBAur+v6Ffr1isx+gSLdtAfSo2T9DRp3lx26fYH 61Pk7i4ZdEeBKeFt41nRt+dSZKTkVrf2WwcWOGG604GO8m8mIew9GBhl6oh2RMcngr nWPZxN7EKV09bs+/4k+XZP7MPAMbmT8i6oq4PU+3RHaha9hrUFZ3xVXuSEh0K1LPtL t8L/T/XWZmADIH4qp7xF7KuMCyV527exMz7uBulMyqdlFejoDpznhZg4yfURFwlJ3P igLxFSY5AuEC45EyEyJXqtNAYOy/tU4SwsU8fLPAlNZNX+S0oldnRx9TKKNgp2hh2+ sXXNbf1tyMWAQ== 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: [RFC PATCH v2 20/25] KVM: nSVM: Do not reset TLB_CONTROL in vmcb02 on nested VM-Enter Date: Tue, 16 Jun 2026 00:41:49 +0000 Message-ID: <20260616004155.1435766-21-yosry@kernel.org> X-Mailer: git-send-email 2.54.0.1136.gdb2ca164c4-goog In-Reply-To: <20260616004155.1435766-1-yosry@kernel.org> References: <20260616004155.1435766-1-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 f91c22e72151e..a226aca8f9108 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); } @@ -981,9 +976,6 @@ 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; -- 2.54.0.1136.gdb2ca164c4-goog