KVM: VMX: Use try_cmpxchg64 in pi_try_set_control

Use try_cmpxchg64 instead of cmpxchg64 (*ptr, old, new) != old
in pi_try_set_control.  cmpxchg returns success in ZF flag, so this
change saves a compare after cmpxchg (and related move instruction
in front of cmpxchg):

  b9:   88 44 24 60             mov    %al,0x60(%rsp)
  bd:   48 89 c8                mov    %rcx,%rax
  c0:   c6 44 24 62 f2          movb   $0xf2,0x62(%rsp)
  c5:   48 8b 74 24 60          mov    0x60(%rsp),%rsi
  ca:   f0 49 0f b1 34 24       lock cmpxchg %rsi,(%r12)
  d0:   48 39 c1                cmp    %rax,%rcx
  d3:   75 cf                   jne    a4 <vmx_vcpu_pi_load+0xa4>

patched:

  c1:   88 54 24 60             mov    %dl,0x60(%rsp)
  c5:   c6 44 24 62 f2          movb   $0xf2,0x62(%rsp)
  ca:   48 8b 54 24 60          mov    0x60(%rsp),%rdx
  cf:   f0 48 0f b1 13          lock cmpxchg %rdx,(%rbx)
  d4:   75 d5                   jne    ab <vmx_vcpu_pi_load+0xab>

Signed-off-by: Uros Bizjak <[email protected]>
Cc: Paolo Bonzini <[email protected]>
Cc: Sean Christopherson <[email protected]>
Cc: Vitaly Kuznetsov <[email protected]>
Cc: Wanpeng Li <[email protected]>
Cc: Jim Mattson <[email protected]>
Cc: Joerg Roedel <[email protected]>
Reported-by: kernel test robot <[email protected]>
Message-Id: <[email protected]>
Signed-off-by: Paolo Bonzini <[email protected]>

0 files changed, 0 insertions, 0 deletions