From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6F52BE81E01 for ; Fri, 6 Oct 2023 14:37:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232533AbjJFOhA (ORCPT ); Fri, 6 Oct 2023 10:37:00 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35652 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232256AbjJFOg6 (ORCPT ); Fri, 6 Oct 2023 10:36:58 -0400 Received: from mail-yw1-x114a.google.com (mail-yw1-x114a.google.com [IPv6:2607:f8b0:4864:20::114a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 995928F for ; Fri, 6 Oct 2023 07:36:56 -0700 (PDT) Received: by mail-yw1-x114a.google.com with SMTP id 00721157ae682-5a2318df875so33619157b3.2 for ; Fri, 06 Oct 2023 07:36:56 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1696603016; x=1697207816; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=i58l4QdfZN6X+tVl9sXUSU5MssTQt5gV2xYo4Yk/tro=; b=AW5UdJMKrweVx1vMeC3UpMFtpMzzGZ6zccr9d0xQCg69lZjKiy8M/ZTytiurPsjUjY E3tnbglEVJXkmaZD5Xiz0gHENMvCCHzEVj/WMXg8DVg/Mwothn+/6b/qlYwjtLWKjFK6 i/qYV+IuYOodck2X1C0yBjt4Cq8bbVHDP/rB4/b6IJJiyp6Y1GgLhg8fVaHZfIlrz9ZE dEUsrfXv/JJr5AFcoQ9qIDoMwadC1BV8D95hjpuuOz2q3onGZbHaSEsdETfFQImInqYy yO/XSt/jrdSRBtJYR7Pc2bdSEOcRXCsvXTgLadOV4r1JCtbYdRhvZ+ocBU2FTOPtHQe1 l8VA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1696603016; x=1697207816; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=i58l4QdfZN6X+tVl9sXUSU5MssTQt5gV2xYo4Yk/tro=; b=bA94PiM35FJE2Ip5ewLrBbfT16HWoav7bRiqWogCPmGIxqGac8kyjGi3z3AeSEjHhD nkVOx4jZBVnjkYohsPZlU87RBoUmXc1Vmv5fiE7ncTFJhE+J5cEyOXnMJEC0XKY3NKOd u5lMb9tTVAPtuUqMjjOB5KQFB1T20dLdSuuXkxN1uAkNJvMeI1R1nNhOWJKJi2fPeeus bjpzVyaFu9WPqagwasTXumDDUwQGlSZCIW5nWE5zkHVpbwg+ThaVJRm/W9TcHK18i0ed 7nrkyDA/wZfepLOrZdbWp0BD6d2bTBGn4vOvsz3ap9gEWQwRIpKC/0E1e+Qr1SAIa4SR jDGQ== X-Gm-Message-State: AOJu0YyD0Sqd4E93pkfm3qDOYjllOmrJ4T8VEMqi5xV0vVoO2gsOKCXt PYQezXuR04lh3cQ49BXMwyxvwDUvUFM= X-Google-Smtp-Source: AGHT+IFQPwuq8dktatytMOhE25UzyzqCNlQC2UUPVzg1lqdTu+UMho1qRpPPz4wW/QHlMjyqJHF5XE+bNrg= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5c37]) (user=seanjc job=sendgmr) by 2002:a25:ae59:0:b0:d7e:752f:baee with SMTP id g25-20020a25ae59000000b00d7e752fbaeemr117773ybe.10.1696603015772; Fri, 06 Oct 2023 07:36:55 -0700 (PDT) Date: Fri, 6 Oct 2023 07:36:54 -0700 In-Reply-To: <20231005131402.14611-5-kirill.shutemov@linux.intel.com> Mime-Version: 1.0 References: <20231005131402.14611-1-kirill.shutemov@linux.intel.com> <20231005131402.14611-5-kirill.shutemov@linux.intel.com> Message-ID: Subject: Re: [PATCH 04/13] x86/kvm: Do not try to disable kvmclock if it was not enabled From: Sean Christopherson To: "Kirill A. Shutemov" Cc: Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "Rafael J. Wysocki" , Peter Zijlstra , Adrian Hunter , Kuppuswamy Sathyanarayanan , Elena Reshetova , Jun Nakajima , Rick Edgecombe , Tom Lendacky , kexec@lists.infradead.org, linux-coco@lists.linux.dev, linux-kernel@vger.kernel.org, Paolo Bonzini Content-Type: text/plain; charset="us-ascii" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org +Paolo Please use get_maintainers... On Thu, Oct 05, 2023, Kirill A. Shutemov wrote: > kvm_guest_cpu_offline() tries to disable kvmclock regardless if it is > present in the VM. It leads to write to a MSR that doesn't exist on some > configurations, namely in TDX guest: > > unchecked MSR access error: WRMSR to 0x12 (tried to write 0x0000000000000000) > at rIP: 0xffffffff8110687c (kvmclock_disable+0x1c/0x30) > > kvmclock enabling is gated by CLOCKSOURCE and CLOCKSOURCE2 KVM paravirt > features. > > Do not disable kvmclock if it was not enumerated or disabled by user > from kernel command line. > > Signed-off-by: Kirill A. Shutemov > Fixes: c02027b5742b ("x86/kvm: Disable kvmclock on all CPUs on shutdown") > --- > arch/x86/kernel/kvmclock.c | 9 +++++++-- > 1 file changed, 7 insertions(+), 2 deletions(-) > > diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c > index fb8f52149be9..cba2e732e53f 100644 > --- a/arch/x86/kernel/kvmclock.c > +++ b/arch/x86/kernel/kvmclock.c > @@ -22,7 +22,7 @@ > #include > #include > > -static int kvmclock __initdata = 1; > +static int kvmclock __ro_after_init = 1; > static int kvmclock_vsyscall __initdata = 1; > static int msr_kvm_system_time __ro_after_init = MSR_KVM_SYSTEM_TIME; > static int msr_kvm_wall_clock __ro_after_init = MSR_KVM_WALL_CLOCK; > @@ -195,7 +195,12 @@ static void kvm_setup_secondary_clock(void) > > void kvmclock_disable(void) > { > - native_write_msr(msr_kvm_system_time, 0, 0); > + if (!kvm_para_available() || !kvmclock) > + return; > + > + if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE) || > + kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE2)) > + native_write_msr(msr_kvm_system_time, 0, 0); Rather than recheck everything and preserve kvmclock, what about leaving the MSR indices '0' by default and then disable msr_kvm_system_time iff it's non-zero. That way the disable path won't become stale if the conditions for enabling kvmclock change. diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c index fb8f52149be9..f2fff625576d 100644 --- a/arch/x86/kernel/kvmclock.c +++ b/arch/x86/kernel/kvmclock.c @@ -24,8 +24,8 @@ static int kvmclock __initdata = 1; static int kvmclock_vsyscall __initdata = 1; -static int msr_kvm_system_time __ro_after_init = MSR_KVM_SYSTEM_TIME; -static int msr_kvm_wall_clock __ro_after_init = MSR_KVM_WALL_CLOCK; +static int msr_kvm_system_time __ro_after_init; +static int msr_kvm_wall_clock __ro_after_init; static u64 kvm_sched_clock_offset __ro_after_init; static int __init parse_no_kvmclock(char *arg) @@ -195,7 +195,8 @@ static void kvm_setup_secondary_clock(void) void kvmclock_disable(void) { - native_write_msr(msr_kvm_system_time, 0, 0); + if (msr_kvm_system_time) + native_write_msr(msr_kvm_system_time, 0, 0); } static void __init kvmclock_init_mem(void) @@ -294,7 +295,10 @@ void __init kvmclock_init(void) if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE2)) { msr_kvm_system_time = MSR_KVM_SYSTEM_TIME_NEW; msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK_NEW; - } else if (!kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE)) { + } else if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE)) { + msr_kvm_system_time = MSR_KVM_SYSTEM_TIME; + msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK; + } else { return; }