Re: [PATCH 3/4] arm64: KVM: let other tasks run when hitting WFE

Marc Zyngier
2013-07-19T14:29:48Z

On 19/07/13 15:25, Will Deacon wrote:
> On Fri, Jul 19, 2013 at 02:53:54PM +0100, Marc Zyngier wrote:
>> So far, when a guest executes WFE (like when waiting for a spinlock
>> to become unlocked), we don't do a thing and let it run uninterrupted.
>>
>> Another option is to trap a blocking WFE and offer the opportunity
>> to the scheduler to switch to another task, potentially giving the
>> vcpu holding the spinlock a chance to run sooner.
>>
>> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
>
> [...]
>
>> +static int kvm_handle_wfx(struct kvm_vcpu *vcpu, struct kvm_run *run)
>> {
>> - kvm_vcpu_block(vcpu);
>> + if (kvm_vcpu_get_hsr(vcpu) & 1)
>> + cond_resched();
>
> The hardcoded `1' doesn't make it obvious that we're treating wfi and wfe
> differently. Could you use a #define for that bit in hsr.iss please?

Good point. I'll rework that part.

M.
--
Jazz is not dead. It just smells funny...