Re: [PATCH v5] KVM: VMX: Execute WBINVD to keep data consistency with assigned devices

Marcelo Tosatti
2010-06-29T18:12:35Z

On Tue, Jun 29, 2010 at 04:50:49PM +0300, Avi Kivity wrote:
> On 06/29/2010 04:35 PM, Marcelo Tosatti wrote:
> >>>
> >>>work_on_cpu() loop instead of smp_call_function_many(), to avoid executing
> >>>wbinvd with interrupts disabled.
> >>Why? wbinvd is not interruptible.
> >Right. But still, smp_call_function_many() is going to busy-spin until
> >the target CPUs finish their work, while work_on_cpu() will schedule.
> >
>
> Good point. So in the worst case we double the hit.
>
> >Also the IPI request has to handled immediately, bypassing the
> >scheduler.
>
> We're screwed on that point in any case, once wbinvd starts the
> scheduler is bypassed.
>
> But work_on_cpu() has its own problems. It creates a kthread
> (perhaps not too bad). Maybe queue_work_on()?

queue_work_on + flush_work should be equivalent to work_on_cpu (without
thread creation).