From nobody Mon Feb 9 06:25:44 2026 Received: from mail-pg1-f202.google.com (mail-pg1-f202.google.com [209.85.215.202]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8C39527FB32 for ; Fri, 9 Jan 2026 03:45:40 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.215.202 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767930341; cv=none; b=Wt0l2DHF/v2rhvqPV+O2JHy0FJ33SXhcnyDchvU0e2MxPM6QmZSOvKzVaEI9XgrGBaqGiR/B+Oy1OIN7yfYc/QmvsKNSBz/1kamWT8EeYGWb1s8ukrMyO9L8vV8yiP5++dyQW+Pjbw9v8Y0YeXg7U8sesRofwqMOQwF7sl2ctjw= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767930341; c=relaxed/simple; bh=ZT0U0x+9g09xqjPT/0E35x3IQPyKy+0Y8xFgFIMYoxo=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=o08bp1z632s47o/QZMiv+r3uulhtzz0Ky+ekLxakduT2fdXsbik38l7DIr0KGlGiLVR/nGGvlGJxJNV6AQOTU4wWJEjt+Kw7/b3N8oKwMkvc41yDhlixoxEA3hQABFGSaPpW/IbY2NJbbRB+GyIC/ji2gCKXN2kC5DBmfPR/XMA= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=w9W5jnfE; arc=none smtp.client-ip=209.85.215.202 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="w9W5jnfE" Received: by mail-pg1-f202.google.com with SMTP id 41be03b00d2f7-c52743b781eso1143920a12.2 for ; Thu, 08 Jan 2026 19:45:40 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1767930340; x=1768535140; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:reply-to:from:to:cc:subject:date:message-id:reply-to; bh=Tw76Itas1ms0nm/HkT0Q/pAxr8UdkEkAfo1cZSDlWBs=; b=w9W5jnfE+T415AKFUGHcuKSAeTkvlo0+LAFr14Y99zvK3R1x6zcrdPoPbzDEocSTaI tHd5K8hPynUiUqBU6xbv5ogviVB5npm3EQM0e/C/LHGf51oMLA0oNN5RescOC4batHqf P5kr04tPYDsI0OpBV+RdURKSY7JX4kx3hmfomj1z60bTV6oflki7bMi4AyWTuHYKrc3A rWdpseGIYCOc8CCH3cjffJrzqPkPg9lVwpjTxEJfHOS33XM20nQpNPNZ7DfDyX0TLgHz 4u2R9xH4UNAwBrJAJ2e7dCImU0gI35JahLa2dqiEbpcBciPsHLuJcVQCK8lKM5t1Jm1c bhmQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1767930340; x=1768535140; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:reply-to:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=Tw76Itas1ms0nm/HkT0Q/pAxr8UdkEkAfo1cZSDlWBs=; b=OFT69kAhzNrTczwDlYrisPahsomdbJJuyoeihR0cUtAc/HZEW/AbqKqvrunC06J0+i cbrSa0pCEFTesWJ2GbPKPlpOltlP281p2vSbzpkz4UXRm7IPulFSQwETMJu2rMMVD1CM kIiBMr7EzEpry5Nh3w9vbLjYk+Y7v7e3BCueRyYS7udN8CN7klvzKZTFGJUII3nkiYR+ HhPBhdC9QZxZE6hmYaipOUGlVbmyhp+41wk1StqirtJzy15DJqVtIJZOLChM0Aa+tYl4 iTdPKirOua99j6IQWiVkQdjx3qY2DN9VEautQJM06D8H8sy4FrFH6LyqG5SNlfwcm1dg RLBA== X-Forwarded-Encrypted: i=1; AJvYcCUWyA4xzI1Yp0CzvoOAvluzwODLU9IVXi4pPsSABZIkupn2I1j/dr3oJitTkPuTenwJmJx9Ph3TcHCEXyw=@vger.kernel.org X-Gm-Message-State: AOJu0YzxyXVESWj4tJQjovCevPU2JlIwlkyUA7nayX5aCkyC9fXWS1Io wNCntLt7mYMoLpl+YKWbLAME42HwiF205B4Os1PqZfFvQw/Uo/IkFeSfVmfjoxkTX5HGcQjfcgo gL9xT4A== X-Google-Smtp-Source: AGHT+IH/lW5NmDB9qcwr9rHXLQVjyDc1n512c0xaZbcjMwhrpfdV6CUAlAwGHdo+o0oKSpFcJVKDWx1AYVI= X-Received: from pjbgb18.prod.google.com ([2002:a17:90b:612:b0:343:af64:f654]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a20:7f9c:b0:364:134a:2bc1 with SMTP id adf61e73a8af0-3898f8cb991mr7774812637.18.1767930339801; Thu, 08 Jan 2026 19:45:39 -0800 (PST) Reply-To: Sean Christopherson Date: Thu, 8 Jan 2026 19:45:27 -0800 In-Reply-To: <20260109034532.1012993-1-seanjc@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260109034532.1012993-1-seanjc@google.com> X-Mailer: git-send-email 2.52.0.457.g6b5491de43-goog Message-ID: <20260109034532.1012993-4-seanjc@google.com> Subject: [PATCH v4 3/8] KVM: nVMX: Switch to vmcs01 to update TPR threshold on-demand if L2 is active From: Sean Christopherson To: Sean Christopherson , Paolo Bonzini Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Chao Gao Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" If KVM updates L1's TPR Threshold while L2 is active, temporarily load vmcs01 and immediately update TPR_THRESHOLD instead of deferring the update until the next nested VM-Exit. Deferring the TPR Threshold update is relatively straightforward, but for several APICv related updates, deferring updates creates ordering and state consistency problems, e.g. KVM at-large thinks APICv is enabled, but vmcs01 is still running with stale (and effectively unknown) state. Reviewed-by: Chao Gao Signed-off-by: Sean Christopherson --- arch/x86/kvm/vmx/nested.c | 4 ---- arch/x86/kvm/vmx/vmx.c | 7 +++---- arch/x86/kvm/vmx/vmx.h | 3 --- 3 files changed, 3 insertions(+), 11 deletions(-) diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c index 920a925bb46f..8efab1cf833f 100644 --- a/arch/x86/kvm/vmx/nested.c +++ b/arch/x86/kvm/vmx/nested.c @@ -2402,7 +2402,6 @@ static void prepare_vmcs02_early(struct vcpu_vmx *vmx= , struct loaded_vmcs *vmcs0 exec_control &=3D ~CPU_BASED_TPR_SHADOW; exec_control |=3D vmcs12->cpu_based_vm_exec_control; =20 - vmx->nested.l1_tpr_threshold =3D -1; if (exec_control & CPU_BASED_TPR_SHADOW) vmcs_write32(TPR_THRESHOLD, vmcs12->tpr_threshold); #ifdef CONFIG_X86_64 @@ -5144,9 +5143,6 @@ void __nested_vmx_vmexit(struct kvm_vcpu *vcpu, u32 v= m_exit_reason, if (kvm_caps.has_tsc_control) vmcs_write64(TSC_MULTIPLIER, vcpu->arch.tsc_scaling_ratio); =20 - if (vmx->nested.l1_tpr_threshold !=3D -1) - vmcs_write32(TPR_THRESHOLD, vmx->nested.l1_tpr_threshold); - if (vmx->nested.change_vmcs01_virtual_apic_mode) { vmx->nested.change_vmcs01_virtual_apic_mode =3D false; vmx_set_virtual_apic_mode(vcpu); diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index 1420665fbb66..3ee86665d8de 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -6827,11 +6827,10 @@ void vmx_update_cr8_intercept(struct kvm_vcpu *vcpu= , int tpr, int irr) nested_cpu_has(vmcs12, CPU_BASED_TPR_SHADOW)) return; =20 + guard(vmx_vmcs01)(vcpu); + tpr_threshold =3D (irr =3D=3D -1 || tpr < irr) ? 0 : irr; - if (is_guest_mode(vcpu)) - to_vmx(vcpu)->nested.l1_tpr_threshold =3D tpr_threshold; - else - vmcs_write32(TPR_THRESHOLD, tpr_threshold); + vmcs_write32(TPR_THRESHOLD, tpr_threshold); } =20 void vmx_set_virtual_apic_mode(struct kvm_vcpu *vcpu) diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h index b44eda6225f4..36f48c4b39c0 100644 --- a/arch/x86/kvm/vmx/vmx.h +++ b/arch/x86/kvm/vmx/vmx.h @@ -184,9 +184,6 @@ struct nested_vmx { u64 pre_vmenter_ssp; u64 pre_vmenter_ssp_tbl; =20 - /* to migrate it to L1 if L2 writes to L1's CR8 directly */ - int l1_tpr_threshold; - u16 vpid02; u16 last_vpid; =20 --=20 2.52.0.457.g6b5491de43-goog