Re: [Intel-gfx] refactor the i915 GVT support

Christoph Hellwig
2021-08-20T14:17:30Z

On Thu, Aug 19, 2021 at 04:29:29PM +0800, Zhenyu Wang wrote:
> I'm working on below patch to resolve this. But I met a weird issue in
> case when building i915 as module and also kvmgt module, it caused
> busy wait on request_module("kvmgt") when boot, it doesn't happen if
> building i915 into kernel. I'm not sure what could be the reason?

Luis, do you know if there is a problem with a request_module from
a driver ->probe routine that is probably called by a module_init
function itself?

In the meantime I'll try to reproduce it locally, but I always had a
hard time getting useful results out of a modular i915, especially
when combined with module paramters. (no blame on i915, just the problem
with modules needed early on).

>
> > But the problem I see is that after moving gvt device model (gvt/*.c
> > except kvmgt.c) into kvmgt module, we'll have issue with initial mmio
> > state which current gvt relies on, that is in design supposed to get
> > initial HW state before i915 driver has taken any operation. Before
> > we can ensure that, I think we may only remove MPT part first but
> > still keep gvt device model as part of i915 with config. I'll try to
> > split that out.
>
> Sorry I misread the code that as we always request kvmgt module when
> gvt init, so it should still apply original method that this isn't a
> problem. Our current validation result has shown no regression as well.

What does initial mmio state mean? This is something new to me. But
as you said in this mail unless I missed something very big it should
work the same as before.

> -static inline void intel_context_unpin(struct intel_context *ce)
> +static inline void _intel_context_unpin(struct intel_context *ce)
> {
> if (!ce->ops->sched_disable) {
> __intel_context_do_unpin(ce, 1);
> @@ -150,6 +150,7 @@ static inline void intel_context_unpin(struct intel_context *ce)
> }
> }
> }
> +void intel_context_unpin(struct intel_context *ce);

Looking at intel_context_unpin/_intel_context_unpin is there really
a need to have this inline to start with? It don't see much the compiler
could optimize by inlining it.