Andrea Arcangeli 74c504a6d7 x86: retpolines: eliminate retpoline from msr event handlers
It's enough to check the value and issue the direct call.

After this commit is applied, here the most common retpolines executed
under a high resolution timer workload in the guest on a VMX host:

[..]
@[
    trace_retpoline+1
    __trace_retpoline+30
    __x86_indirect_thunk_rax+33
    do_syscall_64+89
    entry_SYSCALL_64_after_hwframe+68
]: 267
@[]: 2256
@[
    trace_retpoline+1
    __trace_retpoline+30
    __x86_indirect_thunk_rax+33
    __kvm_wait_lapic_expire+284
    vmx_vcpu_run.part.97+1091
    vcpu_enter_guest+377
    kvm_arch_vcpu_ioctl_run+261
    kvm_vcpu_ioctl+559
    do_vfs_ioctl+164
    ksys_ioctl+96
    __x64_sys_ioctl+22
    do_syscall_64+89
    entry_SYSCALL_64_after_hwframe+68
]: 2390
@[]: 33410

@total: 315707

Note the highest hit above is __delay so probably not worth optimizing
even if it would be more frequent than 2k hits per sec.

Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2019-11-15 11:43:58 +01:00
..
2019-09-20 08:36:47 -07:00
2019-07-14 20:36:12 +02:00
2019-09-19 13:27:23 -07:00
2019-09-15 21:37:14 +02:00
2019-10-12 14:11:21 -07:00