From patchwork Wed May 22 00:17:01 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Woodhouse X-Patchwork-Id: 13669825 Received: from desiato.infradead.org (desiato.infradead.org [90.155.92.199]) (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 8551B1848; Wed, 22 May 2024 00:18:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.92.199 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1716337115; cv=none; b=SjhNWmOf5CE+yEPFUlRsQdYnORK7JERNsAh/BSh/fveasEdcmc9/me4IMWGEgNmHDw/Ah6kIxfx981peHMfr7j//Mx04UiWwdxa7hK66O5C+KvdhS6xoM+cbZz25p3DzufdZF4yULToNGJyz9RtVAGarmZWsLI3VVWRPbzQ08bg= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1716337115; c=relaxed/simple; bh=iOmvqV+vbYDKZG4Z0hPkoNLgaOP2tzUKcwotb2WDGfA=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=AKHNtDJ96WJD7VTb+7rqArw8aEiBrxcLKxhfNXLZHxMRsTJLEwL1cRblt+/yjhZsql7gegOfWphz1HVyRzxNnlNlSr1X4GgHJiVHJwU15A/BmVAlkWYK7J9wLjKNSzjNeTcADrb3nki4cyqNxc4UOtfe6LlUZGTDvZ2SFlmBH0k= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=desiato.srs.infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=VWElfcsH; arc=none smtp.client-ip=90.155.92.199 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=desiato.srs.infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="VWElfcsH" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=Sender:Content-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-ID:Date:Subject:Cc:To:From: Reply-To:Content-Type:Content-ID:Content-Description; bh=vQRg8jTSE/w84X85rubENd1tTskSzNXDiSVdMmVU2k0=; b=VWElfcsH1gVcVWSD8m79ulCmcC SGzPWQVxKrr69y8bkhK2I8P2x2S5EpH2XhMnIszSk6TSU89Jbhx2Nzv81fUQ0mVCP6I6G3bkUf48Q D/G0oUFQYxDuOyyNtUUwc7ippw+t6lMdXXjJq78s+3SAplzr/YZzvTs0lgO39dJXcrT54yuL2qcMX APSYp9VQX7z+adjGQ7Kee0hKMlctaZZKI7om07gEPjpoZW9Uvv2xppQp1XpTJC63nm5pqIXZl93W1 eN5OvncA92UCDBvEff3qYcUQkOTmUw+jDW2A4QUdS47xTZj2SVsNCNP9C+SlRRiIma+FZRud95kxF 2vQz6RLw==; Received: from [2001:8b0:10b:1::ebe] (helo=i7.infradead.org) by desiato.infradead.org with esmtpsa (Exim 4.97.1 #2 (Red Hat Linux)) id 1s9ZgS-000000080jM-3oHr; Wed, 22 May 2024 00:18:23 +0000 Received: from dwoodhou by i7.infradead.org with local (Exim 4.97.1 #2 (Red Hat Linux)) id 1s9ZgR-00000002b4Y-3dFS; Wed, 22 May 2024 01:18:19 +0100 From: David Woodhouse To: kvm@vger.kernel.org Cc: Paolo Bonzini , Jonathan Corbet , Sean Christopherson , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Paul Durrant , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Daniel Bristot de Oliveira , Valentin Schneider , Shuah Khan , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, jalliste@amazon.co.uk, sveith@amazon.de, zide.chen@intel.com, Dongli Zhang , Chenyi Qiang Subject: [RFC PATCH v3 06/21] KVM: x86: Explicitly disable TSC scaling without CONSTANT_TSC Date: Wed, 22 May 2024 01:17:01 +0100 Message-ID: <20240522001817.619072-7-dwmw2@infradead.org> X-Mailer: git-send-email 2.44.0 In-Reply-To: <20240522001817.619072-1-dwmw2@infradead.org> References: <20240522001817.619072-1-dwmw2@infradead.org> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Sender: David Woodhouse X-SRS-Rewrite: SMTP reverse-path rewritten from by desiato.infradead.org. See http://www.infradead.org/rpr.html From: David Woodhouse KVM does make an attempt to cope with non-constant TSC, and has notifiers to handle host TSC frequency changes. However, it *only* adjusts the KVM clock, and doesn't adjust TSC frequency scaling when the host changes. This is presumably because non-constant TSCs were fixed in hardware long before TSC scaling was implemented, so there should never be real CPUs which have TSC scaling but *not* CONSTANT_TSC. Such a combination could potentially happen in some odd L1 nesting environment, but it isn't worth trying to support it. Just make the dependency explicit. Signed-off-by: David Woodhouse Reviewed-by: Paul Durrant --- arch/x86/kvm/svm/svm.c | 3 ++- arch/x86/kvm/vmx/vmx.c | 2 +- 2 files changed, 3 insertions(+), 2 deletions(-) diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c index 0f3b59da0d4a..4d3ec1c3231e 100644 --- a/arch/x86/kvm/svm/svm.c +++ b/arch/x86/kvm/svm/svm.c @@ -5202,7 +5202,8 @@ static __init int svm_hardware_setup(void) kvm_enable_efer_bits(EFER_FFXSR); if (tsc_scaling) { - if (!boot_cpu_has(X86_FEATURE_TSCRATEMSR)) { + if (!boot_cpu_has(X86_FEATURE_TSCRATEMSR) || + !boot_cpu_has(X86_FEATURE_CONSTANT_TSC)) { tsc_scaling = false; } else { pr_info("TSC scaling supported\n"); diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index 6780313914f8..bee830adf744 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -8428,7 +8428,7 @@ __init int vmx_hardware_setup(void) if (!enable_apicv || !cpu_has_vmx_ipiv()) enable_ipiv = false; - if (cpu_has_vmx_tsc_scaling()) + if (cpu_has_vmx_tsc_scaling() && boot_cpu_has(X86_FEATURE_CONSTANT_TSC)) kvm_caps.has_tsc_control = true; kvm_caps.max_tsc_scaling_ratio = KVM_VMX_TSC_MULTIPLIER_MAX;