[PATCH v5] KVM: VMX: Improve handle_external_interrupt_irqoff inline assembly

[PATCH v5] KVM: VMX: Improve handle_external_interrupt_irqoff inline assembly

[Uros Bizjak]

Improve handle_external_interrupt_irqoff inline assembly in several ways:
- remove unneeded %c operand modifiers and "$" prefixes
- use %rsp instead of _ASM_SP, since we are in CONFIG_X86_64 part
- use $-16 immediate to align %rsp
- remove unneeded use of __ASM_SIZE macro
- define "ss" named operand only for X86_64

The patch introduces no functional changes.

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/vmx.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index c2c6335a998c..22f3324600e1 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -6283,13 +6283,13 @@ static void handle_external_interrupt_irqoff(struct kvm_vcpu *vcpu)
 
 	asm volatile(
 #ifdef CONFIG_X86_64
-		"mov %%" _ASM_SP ", %[sp]\n\t"
-		"and $0xfffffffffffffff0, %%" _ASM_SP "\n\t"
-		"push $%c[ss]\n\t"
+		"mov %%rsp, %[sp]\n\t"
+		"and $-16, %%rsp\n\t"
+		"push %[ss]\n\t"
 		"push %[sp]\n\t"
 #endif
 		"pushf\n\t"
-		__ASM_SIZE(push) " $%c[cs]\n\t"
+		"push %[cs]\n\t"
 		CALL_NOSPEC
 		:
 #ifdef CONFIG_X86_64
@@ -6298,7 +6298,9 @@ static void handle_external_interrupt_irqoff(struct kvm_vcpu *vcpu)
 		ASM_CALL_CONSTRAINT
 		:
 		[thunk_target]"r"(entry),
+#ifdef CONFIG_X86_64
 		[ss]"i"(__KERNEL_DS),
+#endif
 		[cs]"i"(__KERNEL_CS)
 	);
 
-- 
2.25.4

Re: [PATCH v5] KVM: VMX: Improve handle_external_interrupt_irqoff inline assembly

[Paolo Bonzini]

On 04/05/20 17:57, Uros Bizjak wrote:
> Improve handle_external_interrupt_irqoff inline assembly in several ways:
> - remove unneeded %c operand modifiers and "$" prefixes
> - use %rsp instead of _ASM_SP, since we are in CONFIG_X86_64 part
> - use $-16 immediate to align %rsp
> - remove unneeded use of __ASM_SIZE macro
> - define "ss" named operand only for X86_64
> 
> The patch introduces no functional changes.
> 
> 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/vmx.c | 10 ++++++----
>  1 file changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index c2c6335a998c..22f3324600e1 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -6283,13 +6283,13 @@ static void handle_external_interrupt_irqoff(struct kvm_vcpu *vcpu)
>  
>  	asm volatile(
>  #ifdef CONFIG_X86_64
> -		"mov %%" _ASM_SP ", %[sp]\n\t"
> -		"and $0xfffffffffffffff0, %%" _ASM_SP "\n\t"
> -		"push $%c[ss]\n\t"
> +		"mov %%rsp, %[sp]\n\t"
> +		"and $-16, %%rsp\n\t"
> +		"push %[ss]\n\t"
>  		"push %[sp]\n\t"
>  #endif
>  		"pushf\n\t"
> -		__ASM_SIZE(push) " $%c[cs]\n\t"
> +		"push %[cs]\n\t"
>  		CALL_NOSPEC
>  		:
>  #ifdef CONFIG_X86_64
> @@ -6298,7 +6298,9 @@ static void handle_external_interrupt_irqoff(struct kvm_vcpu *vcpu)
>  		ASM_CALL_CONSTRAINT
>  		:
>  		[thunk_target]"r"(entry),
> +#ifdef CONFIG_X86_64
>  		[ss]"i"(__KERNEL_DS),
> +#endif
>  		[cs]"i"(__KERNEL_CS)
>  	);
>  
> 

Queued, thanks.

Paolo