linux-kernel - Re: [PATCH] KVM/SVM: Move vmenter.S exception fixups out of line

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Message-ID: <87d6caab-7982-13ee-20a2-8ed69d448ca0@redhat.com>
Date:   Fri, 26 Feb 2021 14:46:23 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Uros Bizjak <ubizjak@...il.com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     Sean Christopherson <seanjc@...gle.com>
Subject: Re: [PATCH] KVM/SVM: Move vmenter.S exception fixups out of line

On 26/02/21 13:56, Uros Bizjak wrote:
> Avoid jump by moving exception fixups out of line.
> 
> Cc: Sean Christopherson <seanjc@...gle.com>
> Cc: Paolo Bonzini <pbonzini@...hat.com>
> Signed-off-by: Uros Bizjak <ubizjak@...il.com>
> ---
>   arch/x86/kvm/svm/vmenter.S | 35 ++++++++++++++++++++---------------
>   1 file changed, 20 insertions(+), 15 deletions(-)
> 
> diff --git a/arch/x86/kvm/svm/vmenter.S b/arch/x86/kvm/svm/vmenter.S
> index 343108bf0f8c..4fa17df123cd 100644
> --- a/arch/x86/kvm/svm/vmenter.S
> +++ b/arch/x86/kvm/svm/vmenter.S
> @@ -80,15 +80,9 @@ SYM_FUNC_START(__svm_vcpu_run)
>   	/* Enter guest mode */
>   	sti
>   
> -3:	vmrun %_ASM_AX
> -	jmp 5f
> -4:	cmpb $0, kvm_rebooting
> -	jne 5f
> -	ud2
> -	_ASM_EXTABLE(3b, 4b)
> +1:	vmrun %_ASM_AX
>   
> -5:
> -	cli
> +2:	cli
>   
>   #ifdef CONFIG_RETPOLINE
>   	/* IMPORTANT: Stuff the RSB immediately after VM-Exit, before RET! */
> @@ -155,6 +149,13 @@ SYM_FUNC_START(__svm_vcpu_run)
>   #endif
>   	pop %_ASM_BP
>   	ret
> +
> +3:	cmpb $0, kvm_rebooting
> +	jne 2b
> +	ud2
> +
> +	_ASM_EXTABLE(1b, 3b)
> +
>   SYM_FUNC_END(__svm_vcpu_run)
>   
>   /**
> @@ -174,18 +175,15 @@ SYM_FUNC_START(__svm_sev_es_vcpu_run)
>   #endif
>   	push %_ASM_BX
>   
> -	/* Enter guest mode */
> +	/* Move @vmcb to RAX. */
>   	mov %_ASM_ARG1, %_ASM_AX
> +
> +	/* Enter guest mode */
>   	sti
>   
>   1:	vmrun %_ASM_AX
> -	jmp 3f
> -2:	cmpb $0, kvm_rebooting
> -	jne 3f
> -	ud2
> -	_ASM_EXTABLE(1b, 2b)
>   
> -3:	cli
> +2:	cli
>   
>   #ifdef CONFIG_RETPOLINE
>   	/* IMPORTANT: Stuff the RSB immediately after VM-Exit, before RET! */
> @@ -205,4 +203,11 @@ SYM_FUNC_START(__svm_sev_es_vcpu_run)
>   #endif
>   	pop %_ASM_BP
>   	ret
> +
> +3:	cmpb $0, kvm_rebooting
> +	jne 2b
> +	ud2
> +
> +	_ASM_EXTABLE(1b, 3b)
> +
>   SYM_FUNC_END(__svm_sev_es_vcpu_run)
> 

Queued, thanks.

Paolo