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

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Message-ID: <ZXnoWuaXvRkJjlDK@google.com>
Date:   Wed, 13 Dec 2023 09:22:34 -0800
From:   Sean Christopherson <seanjc@...gle.com>
To:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        Elena Reshetova <elena.reshetova@...el.com>,
        Jun Nakajima <jun.nakajima@...el.com>,
        Rick Edgecombe <rick.p.edgecombe@...el.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Ashish Kalra <ashish.kalra@....com>,
        Kai Huang <kai.huang@...el.com>, Baoquan He <bhe@...hat.com>,
        kexec@...ts.infradead.org, linux-coco@...ts.linux.dev,
        linux-kernel@...r.kernel.org,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>
Subject: Re: [PATCHv4 05/14] x86/kvm: Do not try to disable kvmclock if it was
 not enabled

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@...ux.intel.com>
> > Fixes: c02027b5742b ("x86/kvm: Disable kvmclock on all CPUs on shutdown")
> > Reviewed-by: Sean Christopherson <seanjc@...gle.com>
> > Reviewed-by: Vitaly Kuznetsov <vkuznets@...hat.com>
> > Cc: Paolo Bonzini <pbonzini@...hat.com>
> > Cc: Wanpeng Li <wanpengli@...cent.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".