[PATCH 2/3] kvmppc: optimize kvm stat handling

[ehrhardt@linux.vnet.ibm.com]

From: Christian Ehrhardt <ehrhardt@linux.vnet.ibm.com>

Currently we use an unneicessary if&switch to detect some cases.
To be honest we don't need the ligh_exits counter anyway, because we can
calculate it out of others. Sum_exits can also be calculated, so we can
remove that too. 
MMIO, DCR  and INTR can be counted on other places without these
additional control structures (The INTR case was never hit anyway).

The handling of BOOKE_INTERRUPT_EXTERNAL/BOOKE_INTERRUPT_DECREMENTER is
similar, but we can avoid the additional if when copying 3 lines of code.
I thought about a goto there to prevent duplicate lines, but rewriting three
lines should be better style than a goto cross switch/case statements (its
also not enough code to justify a new inline function).

Signed-off-by: Christian Ehrhardt <ehrhardt@linux.vnet.ibm.com>
---

[diffstat]
 booke_guest.c |   40 ++++++++++++----------------------------
 1 file changed, 12 insertions(+), 28 deletions(-)

[diff]

diff --git a/arch/powerpc/kvm/booke_guest.c b/arch/powerpc/kvm/booke_guest.c
--- a/arch/powerpc/kvm/booke_guest.c
+++ b/arch/powerpc/kvm/booke_guest.c
@@ -36,11 +36,9 @@
 #define VCPU_STAT(x) offsetof(struct kvm_vcpu, stat.x), KVM_STAT_VCPU
 
 struct kvm_stats_debugfs_item debugfs_entries[] = {
-	{ "exits",      VCPU_STAT(sum_exits) },
 	{ "mmio",       VCPU_STAT(mmio_exits) },
 	{ "dcr",        VCPU_STAT(dcr_exits) },
 	{ "sig",        VCPU_STAT(signal_exits) },
-	{ "light",      VCPU_STAT(light_exits) },
 	{ "itlb_r",     VCPU_STAT(itlb_real_miss_exits) },
 	{ "itlb_v",     VCPU_STAT(itlb_virt_miss_exits) },
 	{ "dtlb_r",     VCPU_STAT(dtlb_real_miss_exits) },
@@ -270,7 +268,16 @@
 		break;
 
 	case BOOKE_INTERRUPT_EXTERNAL:
+		vcpu->stat.ext_intr_exits++;
+		set_last_exit_type(EXT_INTR_EXITS);
+		if (need_resched())
+			cond_resched();
+		r = RESUME_GUEST;
+		break;
+
 	case BOOKE_INTERRUPT_DECREMENTER:
+		vcpu->stat.dec_exits++;
+		set_last_exit_type(DEC_EXITS);
 		/* Since we switched IVPR back to the host's value, the host
 		 * handled this interrupt the moment we enabled interrupts.
 		 * Now we just offer it a chance to reschedule the guest. */
@@ -281,13 +288,6 @@
 		 * misses before ceding control. */
 		if (need_resched())
 			cond_resched();
-		if (exit_nr = BOOKE_INTERRUPT_DECREMENTER) {
-			vcpu->stat.dec_exits++;
-			set_last_exit_type(DEC_EXITS);
-		} else {
-			vcpu->stat.ext_intr_exits++;
-			set_last_exit_type(EXT_INTR_EXITS);
-		}
 		r = RESUME_GUEST;
 		break;
 
@@ -313,6 +313,7 @@
 			break;
 		case EMULATE_DO_DCR:
 			run->exit_reason = KVM_EXIT_DCR;
+			vcpu->stat.dcr_exits++;
 			set_last_exit_type(DCR_EXITS);
 			r = RESUME_HOST;
 			break;
@@ -415,6 +416,7 @@
 			 * actually RAM. */
 			r = kvmppc_emulate_mmio(run, vcpu);
 			set_last_exit_type(MMIO_EXITS);
+			vcpu->stat.mmio_exits++;
 		}
 
 		break;
@@ -485,8 +487,6 @@
 
 	kvmppc_check_and_deliver_interrupts(vcpu);
 
-	/* Do some exit accounting. */
-	vcpu->stat.sum_exits++;
 	if (!(r & RESUME_HOST)) {
 		/* To avoid clobbering exit_reason, only check for signals if
 		 * we aren't already exiting to userspace for some other
@@ -494,24 +494,8 @@
 		if (signal_pending(current)) {
 			run->exit_reason = KVM_EXIT_INTR;
 			r = (-EINTR << 2) | RESUME_HOST | (r & RESUME_FLAG_NV);
-
+			set_last_exit_type(SIGNAL_EXITS);
 			vcpu->stat.signal_exits++;
-			set_last_exit_type(SIGNAL_EXITS);
-		} else {
-			vcpu->stat.light_exits++;
-		}
-	} else {
-		switch (run->exit_reason) {
-		case KVM_EXIT_MMIO:
-			vcpu->stat.mmio_exits++;
-			break;
-		case KVM_EXIT_DCR:
-			vcpu->stat.dcr_exits++;
-			break;
-		case KVM_EXIT_INTR:
-			vcpu->stat.signal_exits++;
-			set_last_exit_type(SIGNAL_EXITS);
-			break;
 		}
 	}