[PATCHv4 05/14] x86/kvm: Do not try to disable kvmclock if it was not enabled

[Kirill A. Shutemov]

On Tue, Dec 05, 2023 at 03:45:01AM +0300, 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 at linux.intel.com>
> Fixes: c02027b5742b ("x86/kvm: Disable kvmclock on all CPUs on shutdown")
> Reviewed-by: Sean Christopherson <seanjc at google.com>
> Reviewed-by: Vitaly Kuznetsov <vkuznets at redhat.com>
> Cc: Paolo Bonzini <pbonzini at redhat.com>
> Cc: Wanpeng Li <wanpengli at tencent.com>

Paolo, Sean, any chance you can get it in through KVM tree while the rest
of kexec patchset is pending? The problem is visible on normal reboot too.

-- 
  Kiryl Shutsemau / Kirill A. Shutemov