| Message ID | 20150718090913.GN14024@cbox |
|---|---|
| State | New |
| Headers | show |
Hi Christoffer, On 07/18/2015 11:09 AM, Christoffer Dall wrote: > On Mon, Jul 06, 2015 at 02:49:55PM +0200, Eric Auger wrote: >> The kvm_vcpu_arch pause field is renamed into power_off to prepare >> for the introduction of a new pause field. >> >> Signed-off-by: Eric Auger <eric.auger@linaro.org> >> >> v4 -> v5: >> - fix compilation issue on arm64 (add power_off field in kvm_host.h) >> --- >> arch/arm/include/asm/kvm_host.h | 4 ++-- >> arch/arm/kvm/arm.c | 10 +++++----- >> arch/arm/kvm/psci.c | 10 +++++----- >> arch/arm64/include/asm/kvm_host.h | 4 ++-- >> 4 files changed, 14 insertions(+), 14 deletions(-) >> >> diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h >> index e896d2c..304004d 100644 >> --- a/arch/arm/include/asm/kvm_host.h >> +++ b/arch/arm/include/asm/kvm_host.h >> @@ -129,8 +129,8 @@ struct kvm_vcpu_arch { >> * here. >> */ >> >> - /* Don't run the guest on this vcpu */ >> - bool pause; >> + /* vcpu power-off state */ >> + bool power_off; >> >> /* IO related fields */ >> struct kvm_decode mmio_decode; >> diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c >> index bcdf799..7537e68 100644 >> --- a/arch/arm/kvm/arm.c >> +++ b/arch/arm/kvm/arm.c >> @@ -475,7 +475,7 @@ static void vcpu_pause(struct kvm_vcpu *vcpu) >> { >> wait_queue_head_t *wq = kvm_arch_vcpu_wq(vcpu); >> >> - wait_event_interruptible(*wq, !vcpu->arch.pause); >> + wait_event_interruptible(*wq, !vcpu->arch.power_off); > > would there be any benefit to simply calling kvm_vcpu_block() instead of > vcpu_pause, and rewrite kvm_arch_vcpu_runnable to: Wouldn't it somehow change the known behavior or kvm_vcpu_block which is expected/used to exit on IRQ/FIQ (WFI). Here it would exit when power_off changes to false (or maybe you meant pause below in the new context?). > > int kvm_arch_vcpu_runnable(struct kvm_vcpu *v) > { > ▸ return !vcpu->arch.power_off && > (!!v->arch.irq_lines || kvm_vgic_vcpu_pending_irq(v)); > } > > Not sure really, certainly the runnable function does not become more > readable. To me the usage of kvm_vcpu_block looks more complex than this code and I would prefer keeping that version if you don't mind. > >> } >> >> static int kvm_vcpu_initialized(struct kvm_vcpu *vcpu) >> @@ -525,7 +525,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run) >> >> update_vttbr(vcpu->kvm); >> >> - if (vcpu->arch.pause) >> + if (vcpu->arch.power_off) >> vcpu_pause(vcpu); > > looking back over this code, how does this actually guarantee that we > don't run a powered-off cpu? > > vcpu_pause() just does a wait_event_interruptible(), so if we get > scheduled again, we'll just proceed running. actually it also checks the !vcpu->arch.power_off condition, right? Is there any case where we > could get scheduled without signal_pending() being true and therefore > inadvertedly run the vcpu? kvm_arm_halt_guest can happen at any time, including after the execution of above vcpu_pause(vcpu) call. This is the reason why I added the second check below, once we entered the critical section and just before running the vcpu. With regard to renamed power_off boolean my understanding is: power_off is set - on kvm_arch_vcpu_ioctl_vcpu_init/KVM_ARM_VCPU_POWER_OFF - on PSCI calls from guests through traps from HVC instructions in that case I don't think this can happen - on KVM_SET_MP_STATE ioctl: I think in that case, what you describe can happen. Do you share the same understanding? Best Regards Eric > > if so, we should change the line below like this: > > diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c > index bc738d2..98f31e6 100644 > --- a/arch/arm/kvm/arm.c > +++ b/arch/arm/kvm/arm.c > @@ -542,7 +542,8 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run) > run->exit_reason = KVM_EXIT_INTR; > } > > - if (ret <= 0 || need_new_vmid_gen(vcpu->kvm)) { > + if (ret <= 0 || need_new_vmid_gen(vcpu->kvm) || > + vcpu->arch.power_off) { > local_irq_enable(); > preempt_enable(); > kvm_timer_sync_hwstate(vcpu); > > > Sorry for polluting your patch with these questions, I'm otherwise fine > with the rename. > > Thanks, > -Christoffer > >> >> /* >> @@ -766,12 +766,12 @@ static int kvm_arch_vcpu_ioctl_vcpu_init(struct kvm_vcpu *vcpu, >> vcpu_reset_hcr(vcpu); >> >> /* >> - * Handle the "start in power-off" case by marking the VCPU as paused. >> + * Handle the "start in power-off" case. >> */ >> if (test_bit(KVM_ARM_VCPU_POWER_OFF, vcpu->arch.features)) >> - vcpu->arch.pause = true; >> + vcpu->arch.power_off = true; >> else >> - vcpu->arch.pause = false; >> + vcpu->arch.power_off = false; >> >> return 0; >> } >> diff --git a/arch/arm/kvm/psci.c b/arch/arm/kvm/psci.c >> index 4b94b51..134971a 100644 >> --- a/arch/arm/kvm/psci.c >> +++ b/arch/arm/kvm/psci.c >> @@ -63,7 +63,7 @@ static unsigned long kvm_psci_vcpu_suspend(struct kvm_vcpu *vcpu) >> >> static void kvm_psci_vcpu_off(struct kvm_vcpu *vcpu) >> { >> - vcpu->arch.pause = true; >> + vcpu->arch.power_off = true; >> } >> >> static unsigned long kvm_psci_vcpu_on(struct kvm_vcpu *source_vcpu) >> @@ -87,7 +87,7 @@ static unsigned long kvm_psci_vcpu_on(struct kvm_vcpu *source_vcpu) >> */ >> if (!vcpu) >> return PSCI_RET_INVALID_PARAMS; >> - if (!vcpu->arch.pause) { >> + if (!vcpu->arch.power_off) { >> if (kvm_psci_version(source_vcpu) != KVM_ARM_PSCI_0_1) >> return PSCI_RET_ALREADY_ON; >> else >> @@ -115,7 +115,7 @@ static unsigned long kvm_psci_vcpu_on(struct kvm_vcpu *source_vcpu) >> * the general puspose registers are undefined upon CPU_ON. >> */ >> *vcpu_reg(vcpu, 0) = context_id; >> - vcpu->arch.pause = false; >> + vcpu->arch.power_off = false; >> smp_mb(); /* Make sure the above is visible */ >> >> wq = kvm_arch_vcpu_wq(vcpu); >> @@ -152,7 +152,7 @@ static unsigned long kvm_psci_vcpu_affinity_info(struct kvm_vcpu *vcpu) >> kvm_for_each_vcpu(i, tmp, kvm) { >> mpidr = kvm_vcpu_get_mpidr_aff(tmp); >> if (((mpidr & target_affinity_mask) == target_affinity) && >> - !tmp->arch.pause) { >> + !tmp->arch.power_off) { >> return PSCI_0_2_AFFINITY_LEVEL_ON; >> } >> } >> @@ -175,7 +175,7 @@ static void kvm_prepare_system_event(struct kvm_vcpu *vcpu, u32 type) >> * re-initialized. >> */ >> kvm_for_each_vcpu(i, tmp, vcpu->kvm) { >> - tmp->arch.pause = true; >> + tmp->arch.power_off = true; >> kvm_vcpu_kick(tmp); >> } >> >> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h >> index 2709db2..009da6b 100644 >> --- a/arch/arm64/include/asm/kvm_host.h >> +++ b/arch/arm64/include/asm/kvm_host.h >> @@ -122,8 +122,8 @@ struct kvm_vcpu_arch { >> * here. >> */ >> >> - /* Don't run the guest */ >> - bool pause; >> + /* vcpu power-off state */ >> + bool power_off; >> >> /* IO related fields */ >> struct kvm_decode mmio_decode; >> -- >> 1.9.1 >>
diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c index bc738d2..98f31e6 100644 --- a/arch/arm/kvm/arm.c +++ b/arch/arm/kvm/arm.c @@ -542,7 +542,8 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run) run->exit_reason = KVM_EXIT_INTR; } - if (ret <= 0 || need_new_vmid_gen(vcpu->kvm)) { + if (ret <= 0 || need_new_vmid_gen(vcpu->kvm) || + vcpu->arch.power_off) { local_irq_enable(); preempt_enable(); kvm_timer_sync_hwstate(vcpu);