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KVM: PPC: Enable lightweight exits again

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The PowerPC C ABI defines that registers r14-r31 need to be preserved across
function calls. Since our exit handler is written in C, we can make use of that
and don't need to reload r14-r31 on every entry/exit cycle.

This technique is also used in the BookE code and is called "lightweight exits"
there. To follow the tradition, it's called the same in Book3S.

So far this optimization was disabled though, as the code didn't do what it was
expected to do, but failed to work.

This patch fixes and enables lightweight exits again.

Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
This commit is contained in:
Alexander Graf 2010-01-04 22:19:25 +01:00 committed by Marcelo Tosatti
parent b480f780f0
commit 97c4cfbe89
2 changed files with 57 additions and 53 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

4
arch/powerpc/kvm/book3s.c
View file

@ -539,8 +539,6 @@ int kvmppc_handle_pagefault(struct kvm_run *run, struct kvm_vcpu *vcpu,
r = kvmppc_emulate_mmio(run, vcpu);
if ( r == RESUME_HOST_NV )
r = RESUME_HOST;
if ( r == RESUME_GUEST_NV )
r = RESUME_GUEST;
}
return r;
@ -645,7 +643,7 @@ int kvmppc_handle_exit(struct kvm_run *run, struct kvm_vcpu *vcpu,
er = kvmppc_emulate_instruction(run, vcpu);
switch (er) {
case EMULATE_DONE:
r = RESUME_GUEST;
r = RESUME_GUEST_NV;
break;
case EMULATE_FAIL:
printk(KERN_CRIT "%s: emulation at %lx failed (%08x)\n",

106
arch/powerpc/kvm/book3s_64_interrupts.S
View file

@ -40,6 +40,26 @@
mtmsrd r0,1
.endm
#define VCPU_LOAD_NVGPRS(vcpu) \
ld r14, VCPU_GPR(r14)(vcpu); \
ld r15, VCPU_GPR(r15)(vcpu); \
ld r16, VCPU_GPR(r16)(vcpu); \
ld r17, VCPU_GPR(r17)(vcpu); \
ld r18, VCPU_GPR(r18)(vcpu); \
ld r19, VCPU_GPR(r19)(vcpu); \
ld r20, VCPU_GPR(r20)(vcpu); \
ld r21, VCPU_GPR(r21)(vcpu); \
ld r22, VCPU_GPR(r22)(vcpu); \
ld r23, VCPU_GPR(r23)(vcpu); \
ld r24, VCPU_GPR(r24)(vcpu); \
ld r25, VCPU_GPR(r25)(vcpu); \
ld r26, VCPU_GPR(r26)(vcpu); \
ld r27, VCPU_GPR(r27)(vcpu); \
ld r28, VCPU_GPR(r28)(vcpu); \
ld r29, VCPU_GPR(r29)(vcpu); \
ld r30, VCPU_GPR(r30)(vcpu); \
ld r31, VCPU_GPR(r31)(vcpu); \
/*****************************************************************************
* *
* Guest entry / exit code that is in kernel module memory (highmem) *
@ -67,12 +87,16 @@ kvm_start_entry:
SAVE_NVGPRS(r1)
/* Save LR */
mflr r14
std r14, _LINK(r1)
std r0, _LINK(r1)
/* Load non-volatile guest state from the vcpu */
VCPU_LOAD_NVGPRS(r4)
/* XXX optimize non-volatile loading away */
kvm_start_lightweight:
ld r9, VCPU_PC(r4) /* r9 = vcpu->arch.pc */
ld r10, VCPU_SHADOW_MSR(r4) /* r10 = vcpu->arch.shadow_msr */
DISABLE_INTERRUPTS
/* Save R1/R2 in the PACA */
@ -81,29 +105,6 @@ kvm_start_lightweight:
ld r3, VCPU_HIGHMEM_HANDLER(r4)
std r3, PACASAVEDMSR(r13)
/* Load non-volatile guest state from the vcpu */
ld r14, VCPU_GPR(r14)(r4)
ld r15, VCPU_GPR(r15)(r4)
ld r16, VCPU_GPR(r16)(r4)
ld r17, VCPU_GPR(r17)(r4)
ld r18, VCPU_GPR(r18)(r4)
ld r19, VCPU_GPR(r19)(r4)
ld r20, VCPU_GPR(r20)(r4)
ld r21, VCPU_GPR(r21)(r4)
ld r22, VCPU_GPR(r22)(r4)
ld r23, VCPU_GPR(r23)(r4)
ld r24, VCPU_GPR(r24)(r4)
ld r25, VCPU_GPR(r25)(r4)
ld r26, VCPU_GPR(r26)(r4)
ld r27, VCPU_GPR(r27)(r4)
ld r28, VCPU_GPR(r28)(r4)
ld r29, VCPU_GPR(r29)(r4)
ld r30, VCPU_GPR(r30)(r4)
ld r31, VCPU_GPR(r31)(r4)
ld r9, VCPU_PC(r4) /* r9 = vcpu->arch.pc */
ld r10, VCPU_SHADOW_MSR(r4) /* r10 = vcpu->arch.shadow_msr */
ld r3, VCPU_TRAMPOLINE_ENTER(r4)
mtsrr0 r3
@ -247,7 +248,6 @@ kvmppc_handler_highmem:
no_dcbz32_off:
/* XXX maybe skip on lightweight? */
std r14, VCPU_GPR(r14)(r12)
std r15, VCPU_GPR(r15)(r12)
std r16, VCPU_GPR(r16)(r12)
@ -267,9 +267,6 @@ no_dcbz32_off:
std r30, VCPU_GPR(r30)(r12)
std r31, VCPU_GPR(r31)(r12)
/* Restore non-volatile host registers (r14 - r31) */
REST_NVGPRS(r1)
/* Save guest PC (R10) */
std r10, VCPU_PC(r12)
@ -351,42 +348,51 @@ kvm_return_point:
/* Jump back to lightweight entry if we're supposed to */
/* go back into the guest */
/* Pass the exit number as 3rd argument to kvmppc_handle_exit */
mr r5, r3
/* Restore r3 (kvm_run) and r4 (vcpu) */
REST_2GPRS(3, r1)
bl KVMPPC_HANDLE_EXIT
#if 0 /* XXX get lightweight exits back */
/* If RESUME_GUEST, get back in the loop */
cmpwi r3, RESUME_GUEST
bne kvm_exit_heavyweight
beq kvm_loop_lightweight
/* put VCPU and KVM_RUN back into place and roll again! */
REST_2GPRS(3, r1)
b kvm_start_lightweight
cmpwi r3, RESUME_GUEST_NV
beq kvm_loop_heavyweight
kvm_exit_heavyweight:
/* Restore non-volatile host registers */
ld r14, _LINK(r1)
mtlr r14
REST_NVGPRS(r1)
kvm_exit_loop:
addi r1, r1, SWITCH_FRAME_SIZE
#else
ld r4, _LINK(r1)
mtlr r4
cmpwi r3, RESUME_GUEST
bne kvm_exit_heavyweight
/* Restore non-volatile host registers (r14 - r31) */
REST_NVGPRS(r1)
addi r1, r1, SWITCH_FRAME_SIZE
blr
kvm_loop_heavyweight:
ld r4, _LINK(r1)
std r4, (16 + SWITCH_FRAME_SIZE)(r1)
/* Load vcpu and cpu_run */
REST_2GPRS(3, r1)
addi r1, r1, SWITCH_FRAME_SIZE
/* Load non-volatile guest state from the vcpu */
VCPU_LOAD_NVGPRS(r4)
b kvm_start_entry
/* Jump back into the beginning of this function */
b kvm_start_lightweight
kvm_exit_heavyweight:
kvm_loop_lightweight:
addi r1, r1, SWITCH_FRAME_SIZE
#endif
/* We'll need the vcpu pointer */
REST_GPR(4, r1)
/* Jump back into the beginning of this function */
b kvm_start_lightweight
blr