On 02/17/2012 11:13 AM, Alexander Graf wrote:
> Instead of checking whether we should reschedule only when we exited
> due to an interrupt, let's always check before entering the guest back
> again. This gets the target more in line with the other archs.
>
> Signed-off-by: Alexander Graf <agraf@xxxxxxx>
> ---
> arch/powerpc/kvm/booke.c | 15 ++++++++++-----
> 1 files changed, 10 insertions(+), 5 deletions(-)
>
> diff --git a/arch/powerpc/kvm/booke.c b/arch/powerpc/kvm/booke.c
> index bfb2092..de30b6d 100644
> --- a/arch/powerpc/kvm/booke.c
> +++ b/arch/powerpc/kvm/booke.c
> @@ -572,6 +572,7 @@ int kvmppc_handle_exit(struct kvm_run *run, struct kvm_vcpu *vcpu,
> unsigned int exit_nr)
> {
> int r = RESUME_HOST;
> + int resched_needed = 1;
>
> /* update before a new last_exit_type is rewritten */
> kvmppc_update_timing_stats(vcpu);
> @@ -602,25 +603,21 @@ int kvmppc_handle_exit(struct kvm_run *run, struct kvm_vcpu *vcpu,
>
> switch (exit_nr) {
> case BOOKE_INTERRUPT_MACHINE_CHECK:
> - kvm_resched(vcpu);
> r = RESUME_GUEST;
> break;
>
> case BOOKE_INTERRUPT_EXTERNAL:
> kvmppc_account_exit(vcpu, EXT_INTR_EXITS);
> - kvm_resched(vcpu);
> r = RESUME_GUEST;
> break;
>
> case BOOKE_INTERRUPT_DECREMENTER:
> kvmppc_account_exit(vcpu, DEC_EXITS);
> - kvm_resched(vcpu);
> r = RESUME_GUEST;
> break;
>
> case BOOKE_INTERRUPT_DOORBELL:
> kvmppc_account_exit(vcpu, DBELL_EXITS);
> - kvm_resched(vcpu);
> r = RESUME_GUEST;
> break;
>
> @@ -869,8 +866,16 @@ int kvmppc_handle_exit(struct kvm_run *run, struct kvm_vcpu *vcpu,
> BUG();
> }
>
> - local_irq_disable();
> + /* make sure we reschedule if we need to */
> + while (resched_needed) {
> + local_irq_disable();
>
> + resched_needed = need_resched();
> + if (resched_needed) {
> + local_irq_enable();
> + cond_resched();
> + }
> + }
> kvmppc_core_prepare_to_enter(vcpu);
>
> if (!(r & RESUME_HOST)) {
kvmppc_core_prepare_to_enter can enable interrupts (and block) if guest
MSR_WE is set. We may take an interrupt that wants a resched after
waking but before interrupts are disabled again.
We also want to check for a resched in kvmppc_vcpu_run. So, the resched
check belongs in kvmppc_core_prepare_to_enter, something like:
/* Check pending exceptions and deliver one, if possible. */
void kvmppc_core_prepare_to_enter(struct kvm_vcpu *vcpu)
{
WARN_ON_ONCE(!irqs_disabled());
while (true) {
if (signal_pending(current))
break;
if (need_resched()) {
local_irq_enable();
cond_resched();
local_irq_disable();
continue;
}
kvmppc_core_check_exceptions(vcpu);
if (vcpu->arch.shared->msr & MSR_WE) {
local_irq_enable();
kvm_vcpu_block(vcpu);
local_irq_disable();
kvmppc_set_exit_type(vcpu,
EMULATED_MTMSRWE_EXITS);
continue;
}
break;
}
}
It would be simpler (both here and in the idle hcall) if we could just
drop support for CONFIG_PREEMPT=n. :-P
-Scott
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