On 17/04/20 13:35, Uros Bizjak wrote:
> Improve handle_external_interrupt_irqoff inline assembly in several ways:
> - use __stringify to use __KERNEL_DS and __KERNEL_CS directly in assembler
What's the advantage of this to pushing cs and ss? We are faking an
interrupt gate, and interrupts push cs and ss not __KERNEL_DS and
__KERNEL_CS.
> - use %rsp instead of _ASM_SP, since we are in CONFIG_X86_64 part
> - use $-16 immediate to align %rsp
> - avoid earlyclobber by using "l" GCC input operand constraint
What is this and where is it documented?!? :)
Paolo
> - avoid temporary by using current_stack_pointer
>
> The patch introduces no functional change.
>
> Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> Cc: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
> Signed-off-by: Uros Bizjak <ubizjak@xxxxxxxxx>
> ---
> arch/x86/kvm/vmx/vmx.c | 19 ++++++-------------
> 1 file changed, 6 insertions(+), 13 deletions(-)
>
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index 01330096ff3e..4b0d5f0044ff 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -6233,9 +6233,6 @@ static void handle_external_interrupt_irqoff(struct kvm_vcpu *vcpu)
> {
> unsigned int vector;
> unsigned long entry;
> -#ifdef CONFIG_X86_64
> - unsigned long tmp;
> -#endif
> gate_desc *desc;
> u32 intr_info;
>
> @@ -6252,23 +6249,19 @@ 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"
> + "and $-16, %%rsp\n\t"
> + "push $" __stringify(__KERNEL_DS) "\n\t"
> "push %[sp]\n\t"
> #endif
> "pushf\n\t"
> - __ASM_SIZE(push) " $%c[cs]\n\t"
> + __ASM_SIZE(push) " $" __stringify(__KERNEL_CS) "\n\t"
> CALL_NOSPEC
> + : ASM_CALL_CONSTRAINT
> :
