diff options
| author | Uros Bizjak <ubizjak@gmail.com> | 2022-05-20 16:37:37 +0200 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2022-06-15 08:11:24 -0400 |
| commit | 0ac304de73b37b66793d6cc1ad3a03886aa79791 (patch) | |
| tree | 522990c19985ab7a8eae835511bddc521e7e2d09 /arch/x86/kvm/vmx/posted_intr.c | |
| parent | aee98a6838d52d5cca14610d228893e9208f4ed1 (diff) | |
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 <ubizjak@gmail.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Sean Christopherson <seanjc@google.com>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: Wanpeng Li <wanpengli@tencent.com>
Cc: Jim Mattson <jmattson@google.com>
Cc: Joerg Roedel <joro@8bytes.org>
Reported-by: kernel test robot <lkp@intel.com>
Message-Id: <20220520143737.62513-1-ubizjak@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch/x86/kvm/vmx/posted_intr.c')
| -rw-r--r-- | arch/x86/kvm/vmx/posted_intr.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/x86/kvm/vmx/posted_intr.c b/arch/x86/kvm/vmx/posted_intr.c index 237a1f40f939..73f60aa480fe 100644 --- a/arch/x86/kvm/vmx/posted_intr.c +++ b/arch/x86/kvm/vmx/posted_intr.c @@ -42,7 +42,7 @@ static int pi_try_set_control(struct pi_desc *pi_desc, u64 old, u64 new) * update must be retried with a fresh snapshot an ON change causes * the cmpxchg to fail. */ - if (cmpxchg64(&pi_desc->control, old, new) != old) + if (!try_cmpxchg64(&pi_desc->control, &old, new)) return -EBUSY; return 0; |