[PATCH v4] KVM: VMX: Improve handle_external_interrupt_irqoff inline assembly

Uros Bizjak
2020-05-03T23:06:04Z

Improve handle_external_interrupt_irqoff inline assembly in several ways:
- use "re" operand constraint instead of "i" and 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 | 14 ++++++++------
1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index c2c6335a998c..56c742effb30 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
@@ -6298,8 +6298,10 @@ static void handle_external_interrupt_irqoff(struct kvm_vcpu *vcpu)
ASM_CALL_CONSTRAINT
:
[thunk_target]"r"(entry),
- [ss]"i"(__KERNEL_DS),
- [cs]"i"(__KERNEL_CS)
+#ifdef CONFIG_X86_64
+ [ss]"re"(__KERNEL_DS),
+#endif
+ [cs]"re"(__KERNEL_CS)
);

kvm_after_interrupt(vcpu);
--
2.25.4