2021-02-26 13:00:09

by Uros Bizjak

Subject: [PATCH] KVM/SVM: Move vmenter.S exception fixups out of line

Avoid jump by moving exception fixups out of line.

Cc: Sean Christopherson <[email protected]>
Cc: Paolo Bonzini <[email protected]>
Signed-off-by: Uros Bizjak <[email protected]>
---
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)
--
2.29.2

2021-02-26 13:49:50

by Paolo Bonzini

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 <[email protected]>
> Cc: Paolo Bonzini <[email protected]>
> Signed-off-by: Uros Bizjak <[email protected]>
> ---
> 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