From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-yw1-f202.google.com (mail-yw1-f202.google.com [209.85.128.202]) (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 E74A326E05 for ; Fri, 6 Oct 2023 14:36:56 +0000 (UTC) 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="sNvJwlHS" Received: by mail-yw1-f202.google.com with SMTP id 00721157ae682-59c0dd156e5so33552307b3.3 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=lists.linux.dev; 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=sNvJwlHS0Br69jE4FPbBN4bnNGfYMnJ2FSwVn2uhGsrUFcgBgevb0EBKbDaxWrOMrh kfbIReqlncQS5dBPEGdtrSgnl11fwFcrP00tFEP+EU7sY+cSuwmQyrQSeLvaFoOdecZB 96uzRtiIRcEg9OQ0OCOJPtMmgyUhTPC2wHdM+cqNRottsWf9ms752926ZlmIC301R9Xf cpSyzTdvKFpXbLetnefubKajDP3qs5dWg+pRRqCo2PgSWeLoUNMppHX7FrRSYxPwkpHL 4LtC/JNxdH2Md6f3Td5/cNsw9QDZAR+JNBqmJ/5j1YTqOqo8sHWaeZjMaB4/BCpByZLX iM+g== 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=OiZYtEhTV6XC64MFHhw+MnXTJcykmXrACxqCguJz1YI0JwXnHsfHHw3zaB724jy90J t+LpFGLcARza2loAX/yuXAni/ug6qYpGD8BaCoBcRn3LQF1dyL8rXhaNRVqKbjEW3GYe 5GyZZWf4Bno5auAbi/jZWL7GS/5LCnQXB+j2oCgKLpsXpwFk9hAYTgSXcQ63rTACgaJ1 CAm7Jza3uzkas0/4SFCCcZG3Q2KY+83nC7zRMcW5U930E2ftsovU+emBAY8ZqWL/YQ5F tAYI6dL018Mfhv0wZOBZfSea5oqNiaQmmlCdPDP4/NLRkec8cXQcBxu6ReeJY67gBpGh vATg== X-Gm-Message-State: AOJu0YwmVUw2Hx7Psk0D8n9ehcQPbCDh1auY23hs7kho8uPs+2Qx36sz bJ0C7wZob2ZBmaKVhNSaCe9xdKGChJY= 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> Precedence: bulk X-Mailing-List: linux-coco@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: 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" +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; }