linux-kernel - Re: [PATCH v2 05/18] x86/reboot: KVM: Disable SVM during reboot via virt/KVM reboot callback

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Date:   Wed, 15 Mar 2023 01:30:35 +0000
From:   "Huang, Kai" <kai.huang@...el.com>
To:     "Christopherson,, Sean" <seanjc@...gle.com>
CC:     "Gao, Chao" <chao.gao@...el.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "x86@...nel.org" <x86@...nel.org>, "bp@...en8.de" <bp@...en8.de>,
        "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "andrew.cooper3@...rix.com" <andrew.cooper3@...rix.com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>
Subject: Re: [PATCH v2 05/18] x86/reboot: KVM: Disable SVM during reboot via
 virt/KVM reboot callback

On Tue, 2023-03-14 at 17:47 -0700, Sean Christopherson wrote:
> > Also, personally I don't particularly like the middle state in patch 04:
> > 
> >   void cpu_emergency_disable_virtualization(void)
> >   {
> >   #if IS_ENABLED(CONFIG_KVM_INTEL)
> > -	cpu_crash_vmclear_loaded_vmcss();
> > -#endif
> > +	cpu_emergency_virt_cb *callback;
> >   
> > -	cpu_emergency_vmxoff();
> > +	rcu_read_lock();
> > +	callback = rcu_dereference(cpu_emergency_virt_callback);
> > +	if (callback)
> > +		callback();
> > +	rcu_read_unlock();
> > +#endif
> > +	/* KVM_AMD doesn't yet utilize the common callback. */
> >   	cpu_emergency_svm_disable();
> >   }
> > 
> > Which eventually got fixed up in patch 05:
> > 
> >   void cpu_emergency_disable_virtualization(void)
> >   {
> > -#if IS_ENABLED(CONFIG_KVM_INTEL)
> > +#if IS_ENABLED(CONFIG_KVM_INTEL) || IS_ENABLED(CONFIG_KVM_AMD)
> >   	cpu_emergency_virt_cb *callback;
> >   
> >   	rcu_read_lock();
> > @@ -830,8 +830,6 @@ void cpu_emergency_disable_virtualization(void)
> >   		callback();
> >   	rcu_read_unlock();
> >   #endif
> > -	/* KVM_AMD doesn't yet utilize the common callback. */
> > -	cpu_emergency_svm_disable();
> >   }
> >   
> > Could we just merge the two patches together? 
> 
> I'd prefer not to squash the two.  I agree it's ugly, but I dislike converting
> VMX and SVM at the same time.  I'm not totally opposed to moving everything in
> one fell swoop, but my preference is to keep them separate.

Sure.