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KVM: ppc: optimize irq delivery path
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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>
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Hollis Blanchard authored and Avi Kivity committed Dec 31, 2008
1 parent 9ab8084 commit d4cf389
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Showing 4 changed files with 140 additions and 156 deletions.
3 changes: 0 additions & 3 deletions arch/powerpc/include/asm/kvm_ppc.h
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Original file line number Diff line number Diff line change
Expand Up @@ -36,9 +36,6 @@ enum emulation_result {
EMULATE_FAIL, /* can't emulate this instruction */
};

extern const unsigned char exception_priority[];
extern const unsigned char priority_exception[];

extern int __kvmppc_vcpu_run(struct kvm_run *kvm_run, struct kvm_vcpu *vcpu);
extern char kvmppc_handlers_start[];
extern unsigned long kvmppc_handler_len;
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100 changes: 67 additions & 33 deletions arch/powerpc/kvm/44x_emulate.c
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Original file line number Diff line number Diff line change
Expand Up @@ -228,39 +228,56 @@ int kvmppc_core_emulate_mtspr(struct kvm_vcpu *vcpu, int sprn, int rs)
vcpu->arch.sprg7 = vcpu->arch.gpr[rs]; break;

case SPRN_IVPR:
vcpu->arch.ivpr = vcpu->arch.gpr[rs]; break;
vcpu->arch.ivpr = vcpu->arch.gpr[rs];
break;
case SPRN_IVOR0:
vcpu->arch.ivor[0] = vcpu->arch.gpr[rs]; break;
vcpu->arch.ivor[BOOKE_IRQPRIO_CRITICAL] = vcpu->arch.gpr[rs];
break;
case SPRN_IVOR1:
vcpu->arch.ivor[1] = vcpu->arch.gpr[rs]; break;
vcpu->arch.ivor[BOOKE_IRQPRIO_MACHINE_CHECK] = vcpu->arch.gpr[rs];
break;
case SPRN_IVOR2:
vcpu->arch.ivor[2] = vcpu->arch.gpr[rs]; break;
vcpu->arch.ivor[BOOKE_IRQPRIO_DATA_STORAGE] = vcpu->arch.gpr[rs];
break;
case SPRN_IVOR3:
vcpu->arch.ivor[3] = vcpu->arch.gpr[rs]; break;
vcpu->arch.ivor[BOOKE_IRQPRIO_INST_STORAGE] = vcpu->arch.gpr[rs];
break;
case SPRN_IVOR4:
vcpu->arch.ivor[4] = vcpu->arch.gpr[rs]; break;
vcpu->arch.ivor[BOOKE_IRQPRIO_EXTERNAL] = vcpu->arch.gpr[rs];
break;
case SPRN_IVOR5:
vcpu->arch.ivor[5] = vcpu->arch.gpr[rs]; break;
vcpu->arch.ivor[BOOKE_IRQPRIO_ALIGNMENT] = vcpu->arch.gpr[rs];
break;
case SPRN_IVOR6:
vcpu->arch.ivor[6] = vcpu->arch.gpr[rs]; break;
vcpu->arch.ivor[BOOKE_IRQPRIO_PROGRAM] = vcpu->arch.gpr[rs];
break;
case SPRN_IVOR7:
vcpu->arch.ivor[7] = vcpu->arch.gpr[rs]; break;
vcpu->arch.ivor[BOOKE_IRQPRIO_FP_UNAVAIL] = vcpu->arch.gpr[rs];
break;
case SPRN_IVOR8:
vcpu->arch.ivor[8] = vcpu->arch.gpr[rs]; break;
vcpu->arch.ivor[BOOKE_IRQPRIO_SYSCALL] = vcpu->arch.gpr[rs];
break;
case SPRN_IVOR9:
vcpu->arch.ivor[9] = vcpu->arch.gpr[rs]; break;
vcpu->arch.ivor[BOOKE_IRQPRIO_AP_UNAVAIL] = vcpu->arch.gpr[rs];
break;
case SPRN_IVOR10:
vcpu->arch.ivor[10] = vcpu->arch.gpr[rs]; break;
vcpu->arch.ivor[BOOKE_IRQPRIO_DECREMENTER] = vcpu->arch.gpr[rs];
break;
case SPRN_IVOR11:
vcpu->arch.ivor[11] = vcpu->arch.gpr[rs]; break;
vcpu->arch.ivor[BOOKE_IRQPRIO_FIT] = vcpu->arch.gpr[rs];
break;
case SPRN_IVOR12:
vcpu->arch.ivor[12] = vcpu->arch.gpr[rs]; break;
vcpu->arch.ivor[BOOKE_IRQPRIO_WATCHDOG] = vcpu->arch.gpr[rs];
break;
case SPRN_IVOR13:
vcpu->arch.ivor[13] = vcpu->arch.gpr[rs]; break;
vcpu->arch.ivor[BOOKE_IRQPRIO_DTLB_MISS] = vcpu->arch.gpr[rs];
break;
case SPRN_IVOR14:
vcpu->arch.ivor[14] = vcpu->arch.gpr[rs]; break;
vcpu->arch.ivor[BOOKE_IRQPRIO_ITLB_MISS] = vcpu->arch.gpr[rs];
break;
case SPRN_IVOR15:
vcpu->arch.ivor[15] = vcpu->arch.gpr[rs]; break;
vcpu->arch.ivor[BOOKE_IRQPRIO_DEBUG] = vcpu->arch.gpr[rs];
break;

default:
return EMULATE_FAIL;
Expand Down Expand Up @@ -295,37 +312,54 @@ int kvmppc_core_emulate_mfspr(struct kvm_vcpu *vcpu, int sprn, int rt)
vcpu->arch.gpr[rt] = vcpu->arch.dbcr1; break;

case SPRN_IVOR0:
vcpu->arch.gpr[rt] = vcpu->arch.ivor[0]; break;
vcpu->arch.gpr[rt] = vcpu->arch.ivor[BOOKE_IRQPRIO_CRITICAL];
break;
case SPRN_IVOR1:
vcpu->arch.gpr[rt] = vcpu->arch.ivor[1]; break;
vcpu->arch.gpr[rt] = vcpu->arch.ivor[BOOKE_IRQPRIO_MACHINE_CHECK];
break;
case SPRN_IVOR2:
vcpu->arch.gpr[rt] = vcpu->arch.ivor[2]; break;
vcpu->arch.gpr[rt] = vcpu->arch.ivor[BOOKE_IRQPRIO_DATA_STORAGE];
break;
case SPRN_IVOR3:
vcpu->arch.gpr[rt] = vcpu->arch.ivor[3]; break;
vcpu->arch.gpr[rt] = vcpu->arch.ivor[BOOKE_IRQPRIO_INST_STORAGE];
break;
case SPRN_IVOR4:
vcpu->arch.gpr[rt] = vcpu->arch.ivor[4]; break;
vcpu->arch.gpr[rt] = vcpu->arch.ivor[BOOKE_IRQPRIO_EXTERNAL];
break;
case SPRN_IVOR5:
vcpu->arch.gpr[rt] = vcpu->arch.ivor[5]; break;
vcpu->arch.gpr[rt] = vcpu->arch.ivor[BOOKE_IRQPRIO_ALIGNMENT];
break;
case SPRN_IVOR6:
vcpu->arch.gpr[rt] = vcpu->arch.ivor[6]; break;
vcpu->arch.gpr[rt] = vcpu->arch.ivor[BOOKE_IRQPRIO_PROGRAM];
break;
case SPRN_IVOR7:
vcpu->arch.gpr[rt] = vcpu->arch.ivor[7]; break;
vcpu->arch.gpr[rt] = vcpu->arch.ivor[BOOKE_IRQPRIO_FP_UNAVAIL];
break;
case SPRN_IVOR8:
vcpu->arch.gpr[rt] = vcpu->arch.ivor[8]; break;
vcpu->arch.gpr[rt] = vcpu->arch.ivor[BOOKE_IRQPRIO_SYSCALL];
break;
case SPRN_IVOR9:
vcpu->arch.gpr[rt] = vcpu->arch.ivor[9]; break;
vcpu->arch.gpr[rt] = vcpu->arch.ivor[BOOKE_IRQPRIO_AP_UNAVAIL];
break;
case SPRN_IVOR10:
vcpu->arch.gpr[rt] = vcpu->arch.ivor[10]; break;
vcpu->arch.gpr[rt] = vcpu->arch.ivor[BOOKE_IRQPRIO_DECREMENTER];
break;
case SPRN_IVOR11:
vcpu->arch.gpr[rt] = vcpu->arch.ivor[11]; break;
vcpu->arch.gpr[rt] = vcpu->arch.ivor[BOOKE_IRQPRIO_FIT];
break;
case SPRN_IVOR12:
vcpu->arch.gpr[rt] = vcpu->arch.ivor[12]; break;
vcpu->arch.gpr[rt] = vcpu->arch.ivor[BOOKE_IRQPRIO_WATCHDOG];
break;
case SPRN_IVOR13:
vcpu->arch.gpr[rt] = vcpu->arch.ivor[13]; break;
vcpu->arch.gpr[rt] = vcpu->arch.ivor[BOOKE_IRQPRIO_DTLB_MISS];
break;
case SPRN_IVOR14:
vcpu->arch.gpr[rt] = vcpu->arch.ivor[14]; break;
vcpu->arch.gpr[rt] = vcpu->arch.ivor[BOOKE_IRQPRIO_ITLB_MISS];
break;
case SPRN_IVOR15:
vcpu->arch.gpr[rt] = vcpu->arch.ivor[15]; break;
vcpu->arch.gpr[rt] = vcpu->arch.ivor[BOOKE_IRQPRIO_DEBUG];
break;

default:
return EMULATE_FAIL;
}
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