Re: [PATCH] KVM: VMX: Remove unneeded __ASM_SIZE usage with POP instruction

[Sean Christopherson <sean.j.christopherson@intel.com>]

On Sun, Apr 26, 2020 at 02:30:38PM +0200, Uros Bizjak wrote:
> POP instruction always operates in word size, no need to
> use __ASM_SIZE macro to force operating mode.

Nit, "always operates in word size" isn't quite correct, it'd be more
accurate to state "POP [mem] defaults to the word size, and the only
legal non-default size is 16 bits, e.g. a 32-bit POP will #UD in 64-bit
mode and vice versa, no need ...".

With a tweaked changelog:

Reviewed-by: Sean Christopherson <sean.j.christopherson@intel.com>
 
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Sean Christopherson <sean.j.christopherson@intel.com>
> Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
> ---
>  arch/x86/kvm/vmx/vmenter.S | 14 +++++++-------
>  1 file changed, 7 insertions(+), 7 deletions(-)
> 
> diff --git a/arch/x86/kvm/vmx/vmenter.S b/arch/x86/kvm/vmx/vmenter.S
> index 87f3f24fef37..94b8794bdd2a 100644
> --- a/arch/x86/kvm/vmx/vmenter.S
> +++ b/arch/x86/kvm/vmx/vmenter.S
> @@ -163,13 +163,13 @@ SYM_FUNC_START(__vmx_vcpu_run)
>  	mov WORD_SIZE(%_ASM_SP), %_ASM_AX
>  
>  	/* Save all guest registers, including RAX from the stack */
> -	__ASM_SIZE(pop) VCPU_RAX(%_ASM_AX)
> -	mov %_ASM_CX,   VCPU_RCX(%_ASM_AX)
> -	mov %_ASM_DX,   VCPU_RDX(%_ASM_AX)
> -	mov %_ASM_BX,   VCPU_RBX(%_ASM_AX)
> -	mov %_ASM_BP,   VCPU_RBP(%_ASM_AX)
> -	mov %_ASM_SI,   VCPU_RSI(%_ASM_AX)
> -	mov %_ASM_DI,   VCPU_RDI(%_ASM_AX)
> +	pop           VCPU_RAX(%_ASM_AX)
> +	mov %_ASM_CX, VCPU_RCX(%_ASM_AX)
> +	mov %_ASM_DX, VCPU_RDX(%_ASM_AX)
> +	mov %_ASM_BX, VCPU_RBX(%_ASM_AX)
> +	mov %_ASM_BP, VCPU_RBP(%_ASM_AX)
> +	mov %_ASM_SI, VCPU_RSI(%_ASM_AX)
> +	mov %_ASM_DI, VCPU_RDI(%_ASM_AX)
>  #ifdef CONFIG_X86_64
>  	mov %r8,  VCPU_R8 (%_ASM_AX)
>  	mov %r9,  VCPU_R9 (%_ASM_AX)
> -- 
> 2.25.3
>