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

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Message-ID: <87pndgnyud.fsf@vitty.brq.redhat.com>
Date:   Fri, 13 Mar 2020 14:55:38 +0100
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     Sean Christopherson <sean.j.christopherson@...el.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()

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.

>  	vmcs12->exit_qualification = exit_qual;
>  	if (enable_shadow_vmcs || vmx->nested.hv_evmcs)
>  		vmx->nested.need_vmcs12_to_shadow_sync = true;

Reviewed-by: Vitaly Kuznetsov <vkuznets@...hat.com>

-- 
Vitaly