[PATCH 24/37] KVM: PPC: booke: rework rescheduling checks

[Alexander Graf]

On 27.02.2012, at 20:28, Scott Wood wrote:

> On 02/24/2012 08:26 AM, Alexander Graf wrote:
>> -void kvmppc_core_prepare_to_enter(struct kvm_vcpu *vcpu)
>> +int kvmppc_core_prepare_to_enter(struct kvm_vcpu *vcpu)
>> {
>> 	unsigned long *pending = &vcpu->arch.pending_exceptions;
>> 	unsigned long old_pending = vcpu->arch.pending_exceptions;
>> @@ -283,6 +283,8 @@ void kvmppc_core_prepare_to_enter(struct kvm_vcpu *vcpu)
>> 
>> 	/* Tell the guest about our interrupt status */
>> 	kvmppc_update_int_pending(vcpu, *pending, old_pending);
>> +
>> +	return 0;
>> }
>> 
>> pfn_t kvmppc_gfn_to_pfn(struct kvm_vcpu *vcpu, gfn_t gfn)
>> diff --git a/arch/powerpc/kvm/booke.c b/arch/powerpc/kvm/booke.c
>> index 9979be1..3fcec2c 100644
>> --- a/arch/powerpc/kvm/booke.c
>> +++ b/arch/powerpc/kvm/booke.c
>> @@ -439,8 +439,9 @@ static void kvmppc_core_check_exceptions(struct kvm_vcpu *vcpu)
>> }
>> 
>> /* Check pending exceptions and deliver one, if possible. */
>> -void kvmppc_core_prepare_to_enter(struct kvm_vcpu *vcpu)
>> +int kvmppc_core_prepare_to_enter(struct kvm_vcpu *vcpu)
>> {
>> +	int r = 0;
>> 	WARN_ON_ONCE(!irqs_disabled());
>> 
>> 	kvmppc_core_check_exceptions(vcpu);
>> @@ -451,8 +452,44 @@ void kvmppc_core_prepare_to_enter(struct kvm_vcpu *vcpu)
>> 		local_irq_disable();
>> 
>> 		kvmppc_set_exit_type(vcpu, EMULATED_MTMSRWE_EXITS);
>> -		kvmppc_core_check_exceptions(vcpu);
>> +		r = 1;
>> 	};
>> +
>> +	return r;
>> +}
>> +
>> +/*
>> + * Common checks before entering the guest world.  Call with interrupts
>> + * disabled.
>> + *
>> + * returns !0 if a signal is pending and check_signal is true
>> + */
>> +static int kvmppc_prepare_to_enter(struct kvm_vcpu *vcpu, bool check_signal)
>> +{
>> +	int r = 0;
>> +
>> +	WARN_ON_ONCE(!irqs_disabled());
>> +	while (true) {
>> +		if (need_resched()) {
>> +			local_irq_enable();
>> +			cond_resched();
>> +			local_irq_disable();
>> +			continue;
>> +		}
>> +
>> +		if (kvmppc_core_prepare_to_enter(vcpu)) {
>> +			/* interrupts got enabled in between, so we
>> +			   are back at square 1 */
>> +			continue;
>> +		}
>> +
>> +
>> +		if (check_signal && signal_pending(current))
>> +			r = 1;
> 
> If there is a signal pending and MSR[WE] is set, we'll loop forever
> without reaching this check.

Good point. How about something like this on top (will fold in later)?

diff --git a/arch/powerpc/kvm/booke.c b/arch/powerpc/kvm/booke.c
index 430055e..9f27258 100644
--- a/arch/powerpc/kvm/booke.c
+++ b/arch/powerpc/kvm/booke.c
@@ -477,15 +477,17 @@ static int kvmppc_prepare_to_enter(struct kvm_vcpu *vcpu)
                        continue;
                }
 
+               if (signal_pending(current)) {
+                       r = 1;
+                       break;
+               }
+
                if (kvmppc_core_prepare_to_enter(vcpu)) {
                        /* interrupts got enabled in between, so we
                           are back at square 1 */
                        continue;
                }
 
-               if (signal_pending(current))
-                       r = 1;
-
                break;
        }
 

Alex