[PATCH v6 40/44] KVM: VMX: Set MSR index auto-load entry if and only if entry is "new"

[Mi, Dapeng]

On 12/6/2025 8:17 AM, Sean Christopherson wrote:
> When adding an MSR to the auto-load lists, update the MSR index in the
> list entry if and only if a new entry is being inserted, as 'i' can only
> be non-negative if vmx_find_loadstore_msr_slot() found an entry with the
> MSR's index.  Unnecessarily setting the index is benign, but it makes it
> harder to see that updating the value is necessary even when an existing
> entry for the MSR was found.
>
> No functional change intended.
>
> Signed-off-by: Sean Christopherson <seanjc at google.com>
> ---
>  arch/x86/kvm/vmx/vmx.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index 2c50ebf4ff1b..be2a2580e8f1 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -1141,16 +1141,16 @@ static void add_atomic_switch_msr(struct vcpu_vmx *vmx, unsigned msr,
>  
>  	if (i < 0) {
>  		i = m->guest.nr++;
> +		m->guest.val[i].index = msr;
>  		vmcs_write32(VM_ENTRY_MSR_LOAD_COUNT, m->guest.nr);
>  	}
> -	m->guest.val[i].index = msr;
>  	m->guest.val[i].value = guest_val;
>  
>  	if (j < 0) {
>  		j = m->host.nr++;
> +		m->host.val[j].index = msr;
>  		vmcs_write32(VM_EXIT_MSR_LOAD_COUNT, m->host.nr);
>  	}
> -	m->host.val[j].index = msr;
>  	m->host.val[j].value = host_val;
>  }
>  

Reviewed-by: Dapeng Mi <dapeng1.mi at linux.intel.com>