linux-kernel - Re: [PATCH v2 12/49] KVM: x86: Reject disabling of MWAIT/HLT interception when not allowed

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Message-ID: <ZlYo67vO5JJ6aCAK@google.com>
Date: Tue, 28 May 2024 11:56:43 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Binbin Wu <binbin.wu@...ux.intel.com>
Cc: Paolo Bonzini <pbonzini@...hat.com>, Vitaly Kuznetsov <vkuznets@...hat.com>, kvm@...r.kernel.org, 
	linux-kernel@...r.kernel.org, Hou Wenlong <houwenlong.hwl@...group.com>, 
	Kechen Lu <kechenl@...dia.com>, Oliver Upton <oliver.upton@...ux.dev>, 
	Maxim Levitsky <mlevitsk@...hat.com>, Yang Weijiang <weijiang.yang@...el.com>, 
	Robert Hoo <robert.hoo.linux@...il.com>
Subject: Re: [PATCH v2 12/49] KVM: x86: Reject disabling of MWAIT/HLT
 interception when not allowed

On Wed, May 22, 2024, Binbin Wu wrote:
> On 5/18/2024 1:38 AM, Sean Christopherson wrote:
> > @@ -4726,15 +4740,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
> >   		r = KVM_CLOCK_VALID_FLAGS;
> >   		break;
> >   	case KVM_CAP_X86_DISABLE_EXITS:
> > -		r = KVM_X86_DISABLE_EXITS_PAUSE;
> > -
> > -		if (!mitigate_smt_rsb) {
> > -			r |= KVM_X86_DISABLE_EXITS_HLT |
> > -			     KVM_X86_DISABLE_EXITS_CSTATE;
> > -
> > -			if (kvm_can_mwait_in_guest())
> > -				r |= KVM_X86_DISABLE_EXITS_MWAIT;
> > -		}
> > +		r |= kvm_get_allowed_disable_exits();
> 
> Nit: Just use "=".

Yowsers, that's more than a nit, that's downright bad code, it just happens to be
functionally ok.  Thanks again for the reviews!