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Date:   Fri, 20 Oct 2023 08:32:05 -0700
In-Reply-To: <20231020151242.1814-5-kirill.shutemov@linux.intel.com>
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References: <20231020151242.1814-1-kirill.shutemov@linux.intel.com> <20231020151242.1814-5-kirill.shutemov@linux.intel.com>
Message-ID: <ZTKddZEUyL3QQB6_@google.com>
Subject: Re: [PATCHv2 04/13] x86/kvm: Do not try to disable kvmclock if it was
 not enabled
From:   Sean Christopherson <seanjc@google.com>
To:     "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc:     Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Dave Hansen <dave.hansen@linux.intel.com>, x86@kernel.org,
        "Rafael J. Wysocki" <rafael@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Adrian Hunter <adrian.hunter@intel.com>,
        Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@linux.intel.com>,
        Elena Reshetova <elena.reshetova@intel.com>,
        Jun Nakajima <jun.nakajima@intel.com>,
        Rick Edgecombe <rick.p.edgecombe@intel.com>,
        Tom Lendacky <thomas.lendacky@amd.com>,
        Ashish Kalra <ashish.kalra@amd.com>,
        Kai Huang <kai.huang@intel.com>, Baoquan He <bhe@redhat.com>,
        kexec@lists.infradead.org, linux-coco@lists.linux.dev,
        linux-kernel@vger.kernel.org, Paolo Bonzini <pbonzini@redhat.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        Vitaly Kuznetsov <vkuznets@redhat.com>
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On Fri, Oct 20, 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 enabled.
> 
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> Fixes: c02027b5742b ("x86/kvm: Disable kvmclock on all CPUs on shutdown")
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Wanpeng Li <wanpengli@tencent.com>
> Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
> Cc: Sean Christopherson <seanjc@google.com>
> ---

Reviewed-by: Sean Christopherson <seanjc@google.com>