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Date: Tue, 9 Jan 2024 06:59:16 -0800
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Subject: Re: [PATCHv4 05/14] 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: Paolo Bonzini <pbonzini@redhat.com>, 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, Vitaly Kuznetsov <vkuznets@redhat.com>, 
	Wanpeng Li <wanpengli@tencent.com>
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On Thu, Jan 04, 2024, Kirill A. Shutemov wrote:
> On Wed, Dec 13, 2023 at 09:22:34AM -0800, Sean Christopherson wrote:
> > On Tue, Dec 12, 2023, Kirill A. Shutemov wrote:
> > > 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@linux.intel.com>
> > > > Fixes: c02027b5742b ("x86/kvm: Disable kvmclock on all CPUs on shutdown")
> > > > Reviewed-by: Sean Christopherson <seanjc@google.com>
> > > > Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
> > > > Cc: Paolo Bonzini <pbonzini@redhat.com>
> > > > Cc: Wanpeng Li <wanpengli@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.
> > 
> > Paolo is going to grab this (possibly for 6.7-rc?).  I'll keep this tagged on my
> > end in case that doesn't happen "soon".
> 
> Sean, any update on this?

'Tis now in kvm/next, commit 1c6d984f523f ("x86/kvm: Do not try to disable kvmclock
if it was not enabled").  The one time procrastinating on responding actually worked. ;-)