KVM: retpolines: x86: eliminate retpoline from svm.c exit handlers
It's enough to check the exit value and issue a direct call to avoid
the retpoline for all the common vmexit reasons.
After this commit is applied, here the most common retpolines executed
under a high resolution timer workload in the guest on a SVM host:
[..]
@[
trace_retpoline+1
__trace_retpoline+30
__x86_indirect_thunk_rax+33
ktime_get_update_offsets_now+70
hrtimer_interrupt+131
smp_apic_timer_interrupt+106
apic_timer_interrupt+15
start_sw_timer+359
restart_apic_timer+85
kvm_set_msr_common+1497
msr_interception+142
vcpu_enter_guest+684
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
]: 1940
@[
trace_retpoline+1
__trace_retpoline+30
__x86_indirect_thunk_r12+33
force_qs_rnp+217
rcu_gp_kthread+1270
kthread+268
ret_from_fork+34
]: 4644
@[]: 25095
@[
trace_retpoline+1
__trace_retpoline+30
__x86_indirect_thunk_rax+33
lapic_next_event+28
clockevents_program_event+148
hrtimer_start_range_ns+528
start_sw_timer+356
restart_apic_timer+85
kvm_set_msr_common+1497
msr_interception+142
vcpu_enter_guest+684
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
]: 41474
@[
trace_retpoline+1
__trace_retpoline+30
__x86_indirect_thunk_rax+33
clockevents_program_event+148
hrtimer_start_range_ns+528
start_sw_timer+356
restart_apic_timer+85
kvm_set_msr_common+1497
msr_interception+142
vcpu_enter_guest+684
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
]: 41474
@[
trace_retpoline+1
__trace_retpoline+30
__x86_indirect_thunk_rax+33
ktime_get+58
clockevents_program_event+84
hrtimer_start_range_ns+528
start_sw_timer+356
restart_apic_timer+85
kvm_set_msr_common+1497
msr_interception+142
vcpu_enter_guest+684
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
]: 41887
@[
trace_retpoline+1
__trace_retpoline+30
__x86_indirect_thunk_rax+33
lapic_next_event+28
clockevents_program_event+148
hrtimer_try_to_cancel+168
hrtimer_cancel+21
kvm_set_lapic_tscdeadline_msr+43
kvm_set_msr_common+1497
msr_interception+142
vcpu_enter_guest+684
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
]: 42723
@[
trace_retpoline+1
__trace_retpoline+30
__x86_indirect_thunk_rax+33
clockevents_program_event+148
hrtimer_try_to_cancel+168
hrtimer_cancel+21
kvm_set_lapic_tscdeadline_msr+43
kvm_set_msr_common+1497
msr_interception+142
vcpu_enter_guest+684
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
]: 42766
@[
trace_retpoline+1
__trace_retpoline+30
__x86_indirect_thunk_rax+33
ktime_get+58
clockevents_program_event+84
hrtimer_try_to_cancel+168
hrtimer_cancel+21
kvm_set_lapic_tscdeadline_msr+43
kvm_set_msr_common+1497
msr_interception+142
vcpu_enter_guest+684
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
]: 42848
@[
trace_retpoline+1
__trace_retpoline+30
__x86_indirect_thunk_rax+33
ktime_get+58
start_sw_timer+279
restart_apic_timer+85
kvm_set_msr_common+1497
msr_interception+142
vcpu_enter_guest+684
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
]: 499845
@total: 1780243
SVM has no TSC based programmable preemption timer so it is invoking
ktime_get() frequently.
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>