KVM: ppc: optimize irq delivery path

In kvmppc_deliver_interrupt is just one case left in the switch and it is a
rare one (less than 8%) when looking at the exit numbers. Therefore we can
at least drop the switch/case and if an if. I inserted an unlikely too, but
that's open for discussion.

In kvmppc_can_deliver_interrupt all frequent cases are in the default case.
I know compilers are smart but we can make it easier for them. By writing
down all options and removing the default case combined with the fact that
ithe values are constants 0..15 should allow the compiler to write an easy
jump table.
Modifying kvmppc_can_deliver_interrupt pointed me to the fact that gcc seems
to be unable to reduce priority_exception[x] to a build time constant.
Therefore I changed the usage of the translation arrays in the interrupt
delivery path completely. It is now using priority without translation to irq
on the full irq delivery path.
To be able to do that ivpr regs are stored by their priority now.

Additionally the decision made in kvmppc_can_deliver_interrupt is already
sufficient to get the value of interrupt_msr_mask[x]. Therefore we can replace
the 16x4byte array used here with a single 4byte variable (might still be one
miss, but the chance to find this in cache should be better than the right
entry of the whole array).

Signed-off-by: Christian Ehrhardt <ehrhardt@linux.vnet.ibm.com>
Signed-off-by: Hollis Blanchard <hollisb@us.ibm.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

1 files changed, 18 insertions, 0 deletions

diff --git a/arch/powerpc/kvm/booke.h b/arch/powerpc/kvm/booke.h
index f694a4b2dafa..48d905fd60ab 100644
--- a/arch/powerpc/kvm/booke.h
+++ b/arch/powerpc/kvm/booke.h
@@ -23,6 +23,24 @@
 #include <linux/types.h>
 #include <linux/kvm_host.h>
 
+/* interrupt priortity ordering */
+#define BOOKE_IRQPRIO_DATA_STORAGE 0
+#define BOOKE_IRQPRIO_INST_STORAGE 1
+#define BOOKE_IRQPRIO_ALIGNMENT 2
+#define BOOKE_IRQPRIO_PROGRAM 3
+#define BOOKE_IRQPRIO_FP_UNAVAIL 4
+#define BOOKE_IRQPRIO_SYSCALL 5
+#define BOOKE_IRQPRIO_AP_UNAVAIL 6
+#define BOOKE_IRQPRIO_DTLB_MISS 7
+#define BOOKE_IRQPRIO_ITLB_MISS 8
+#define BOOKE_IRQPRIO_MACHINE_CHECK 9
+#define BOOKE_IRQPRIO_DEBUG 10
+#define BOOKE_IRQPRIO_CRITICAL 11
+#define BOOKE_IRQPRIO_WATCHDOG 12
+#define BOOKE_IRQPRIO_EXTERNAL 13
+#define BOOKE_IRQPRIO_FIT 14
+#define BOOKE_IRQPRIO_DECREMENTER 15
+
 /* Helper function for "full" MSR writes. No need to call this if only EE is
  * changing. */
 static inline void kvmppc_set_msr(struct kvm_vcpu *vcpu, u32 new_msr)