KVM: PPC: Book3S HV: Fix "rm_exit" entry in debugfs timings

At debugfs/kvm/<pid>/vcpu0/timings we show how long each part of the
code takes to run:

$ cat /sys/kernel/debug/kvm/*-*/vcpu0/timings
rm_entry: 123785 49398892 118 4898
rm_intr: 123780 6075890 22 390
rm_exit: 0 0 0 0                     <-- NOK
guest: 123780 46732919988 402 9997638
cede: 0 0 0 0                        <-- OK, no cede napping in P9

The "rm_exit" is always showing zero because it is the last one and
end_timing does not increment the counter of the previous entry.

We can fix it by calling accumulate_time again instead of
end_timing. That way the counter gets incremented. The rest of the
arithmetic can be ignored because there are no timing points after
this and the accumulators are reset before the next round.
Signed-off-by: Fabiano Rosas <farosas@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220525130554.2614394-2-farosas@linux.ibm.com

arch/powerpc/kvm/book3s_hv_p9_entry.c

@@ -438,15 +438,6 @@ void restore_p9_host_os_sprs(struct kvm_vcpu *vcpu,
 EXPORT_SYMBOL_GPL(restore_p9_host_os_sprs);
 
 #ifdef CONFIG_KVM_BOOK3S_HV_EXIT_TIMING
-static void __start_timing(struct kvm_vcpu *vcpu, struct kvmhv_tb_accumulator *next)
-{
-	struct kvmppc_vcore *vc = vcpu->arch.vcore;
-	u64 tb = mftb() - vc->tb_offset_applied;
-
-	vcpu->arch.cur_activity = next;
-	vcpu->arch.cur_tb_start = tb;
-}
-
 static void __accumulate_time(struct kvm_vcpu *vcpu, struct kvmhv_tb_accumulator *next)
 {
 	struct kvmppc_vcore *vc = vcpu->arch.vcore;
@@ -478,8 +469,8 @@ static void __accumulate_time(struct kvm_vcpu *vcpu, struct kvmhv_tb_accumulator
 	curr->seqcount = seq + 2;
 }
 
-#define start_timing(vcpu, next) __start_timing(vcpu, next)
-#define end_timing(vcpu) __start_timing(vcpu, NULL)
+#define start_timing(vcpu, next) __accumulate_time(vcpu, next)
+#define end_timing(vcpu) __accumulate_time(vcpu, NULL)
 #define accumulate_time(vcpu, next) __accumulate_time(vcpu, next)
 #else
 #define start_timing(vcpu, next) do {} while (0)