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[91.219.240.8]) by smtp.gmail.com with ESMTPSA id k13-20020a50c8cd000000b0053443c8fd90sm1642437edh.24.2023.10.20.08.41.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 20 Oct 2023 08:41:14 -0700 (PDT) From: Vitaly Kuznetsov To: "Kirill A. Shutemov" , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org Cc: "Rafael J. Wysocki" , Peter Zijlstra , Adrian Hunter , Kuppuswamy Sathyanarayanan , Elena Reshetova , Jun Nakajima , Rick Edgecombe , Tom Lendacky , "Kalra, Ashish" , Sean Christopherson , "Huang, Kai" , Baoquan He , kexec@lists.infradead.org, linux-coco@lists.linux.dev, linux-kernel@vger.kernel.org, "Kirill A. Shutemov" , Paolo Bonzini , Wanpeng Li Subject: Re: [PATCHv2 04/13] x86/kvm: Do not try to disable kvmclock if it was not enabled In-Reply-To: <20231020151242.1814-5-kirill.shutemov@linux.intel.com> References: <20231020151242.1814-1-kirill.shutemov@linux.intel.com> <20231020151242.1814-5-kirill.shutemov@linux.intel.com> Date: Fri, 20 Oct 2023 17:41:12 +0200 Message-ID: <87wmvh47zb.fsf@redhat.com> MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20231020_084124_956617_E5EC18DD X-CRM114-Status: GOOD ( 21.95 ) X-BeenThere: kexec@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "kexec" Errors-To: kexec-bounces+kexec=archiver.kernel.org@lists.infradead.org "Kirill A. Shutemov" writes: > 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 enabled. > > Signed-off-by: Kirill A. Shutemov > Fixes: c02027b5742b ("x86/kvm: Disable kvmclock on all CPUs on shutdown") > Cc: Paolo Bonzini > Cc: Wanpeng Li > Cc: Vitaly Kuznetsov > Cc: Sean Christopherson > --- > arch/x86/kernel/kvmclock.c | 12 ++++++++---- > 1 file changed, 8 insertions(+), 4 deletions(-) > > 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; > } This should work, so Reviewed-by: Vitaly Kuznetsov but my personal preference would be to change kvm_guest_cpu_offline() to check KVM features explicitly instead of checking MSRs against '0' at least becase it already does so for other features. Completely untested: diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c index b8ab9ee5896c..1ee49c98e70a 100644 --- a/arch/x86/kernel/kvm.c +++ b/arch/x86/kernel/kvm.c @@ -454,7 +454,9 @@ static void kvm_guest_cpu_offline(bool shutdown) kvm_pv_disable_apf(); if (!shutdown) apf_task_wake_all(); - kvmclock_disable(); + if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE2) || + kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE)) + kvmclock_disable(); } -- Vitaly _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec