linux-kernel - Re: [PATCH 06/10] KVM: nVMX: Convert local exit_reason to u16 in ...enter_non_root

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Date:   Mon, 16 Mar 2020 22:29:22 -0700
From:   Sean Christopherson <sean.j.christopherson@...el.com>
To:     Vitaly Kuznetsov <vkuznets@...hat.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, Xiaoyao Li <xiaoyao.li@...el.com>
Subject: Re: [PATCH 06/10] KVM: nVMX: Convert local exit_reason to u16 in
 ...enter_non_root_mode()

On Fri, Mar 13, 2020 at 02:55:38PM +0100, Vitaly Kuznetsov wrote:
> Sean Christopherson <sean.j.christopherson@...el.com> writes:
> 
> > Use a u16 for nested_vmx_enter_non_root_mode()'s local "exit_reason" to
> > make it clear the intermediate code is only responsible for setting the
> > basic exit reason, e.g. FAILED_VMENTRY is unconditionally OR'd in when
> > emulating a failed VM-Entry.
> >
> > No functional change intended.
> >
> > Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
> > ---
> >  arch/x86/kvm/vmx/nested.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
> > index 1848ca0116c0..8fbbe2152ab7 100644
> > --- a/arch/x86/kvm/vmx/nested.c
> > +++ b/arch/x86/kvm/vmx/nested.c
> > @@ -3182,7 +3182,7 @@ enum nvmx_vmentry_status nested_vmx_enter_non_root_mode(struct kvm_vcpu *vcpu,
> >  	struct vcpu_vmx *vmx = to_vmx(vcpu);
> >  	struct vmcs12 *vmcs12 = get_vmcs12(vcpu);
> >  	bool evaluate_pending_interrupts;
> > -	u32 exit_reason = EXIT_REASON_INVALID_STATE;
> > +	u16 exit_reason = EXIT_REASON_INVALID_STATE;
> >  	u32 exit_qual;
> >  
> >  	evaluate_pending_interrupts = exec_controls_get(vmx) &
> > @@ -3308,7 +3308,7 @@ enum nvmx_vmentry_status nested_vmx_enter_non_root_mode(struct kvm_vcpu *vcpu,
> >  		return NVMX_VMENTRY_VMEXIT;
> >  
> >  	load_vmcs12_host_state(vcpu, vmcs12);
> > -	vmcs12->vm_exit_reason = exit_reason | VMX_EXIT_REASONS_FAILED_VMENTRY;
> > +	vmcs12->vm_exit_reason = VMX_EXIT_REASONS_FAILED_VMENTRY | exit_reason;
> 
> My personal preference would be to do
>  (u32)exit_reason | VMX_EXIT_REASONS_FAILED_VMENTRY 
> instead but maybe I'm just not in love with implicit type convertion in C.

Either way works for me.  Paolo?