Re: [PATCH] kvm:vmx:code changes in handle_io() to save some CPU cycles.

[Paolo Bonzini]

On 10/12/20 09:15, Stephen Zhang wrote:
code changes in handle_io() to save some CPU cycles.
Signed-off-by: Stephen Zhang <starzhang...@gmail.com>
---
  arch/x86/kvm/vmx/vmx.c | 5 ++---
  1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 47b8357..109bcf64 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -4899,15 +4899,14 @@ static int handle_triple_fault(struct kvm_vcpu *vcpu)
  static int handle_io(struct kvm_vcpu *vcpu)
  {
        unsigned long exit_qualification;
-       int size, in, string;
+       int size, in;
        unsigned port;
  
  	exit_qualification = vmx_get_exit_qual(vcpu);
-       string = (exit_qualification & 16) != 0;
  
  	++vcpu->stat.io_exits;
  
-	if (string)
+       if (exit_qualification & 16)
                return kvm_emulate_instruction(vcpu, 0);
  
  	port = exit_qualification >> 16;


I would be very surprised if there's any change in the assembly code 
after this patch.

Paolo