linux-kernel - RE: [PATCH RFC] paravirt_ops: refactor struct paravirt_ops into smaller pv_*

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Message-ID: <97D612E30E1F88419025B06CB4CF1BE1039B6D3E@scsmsx412.amr.corp.intel.com>
Date:	Fri, 28 Sep 2007 17:19:07 -0700
From:	"Nakajima, Jun" <jun.nakajima@...el.com>
To:	"Jeremy Fitzhardinge" <jeremy@...p.org>
Cc:	"Andi Kleen" <ak@...e.de>, "Zachary Amsden" <zach@...are.com>,
	"Rusty Russell" <rusty@...tcorp.com.au>,
	"Avi Kivity" <avi@...ranet.com>,
	"Glauber de Oliveira Costa" <glommer@...il.com>,
	"Anthony Liguori" <anthony@...emonkey.ws>,
	"Virtualization Mailing List" <virtualization@...ts.osdl.org>,
	"Ingo Molnar" <mingo@...e.hu>,
	"Thomas Gleixner" <tglx@...utronix.de>,
	"Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>,
	"Alan Cox" <alan@...rguk.ukuu.org.uk>
Subject: RE: [PATCH RFC] paravirt_ops: refactor struct paravirt_ops into smaller pv_*_ops

Jeremy Fitzhardinge wrote:
> Nakajima, Jun wrote:
> > Jeremy Fitzhardinge wrote:
> > 
> > 
> > > +	.pv_irq_ops = {
> > > +		 .init_IRQ = native_init_IRQ,
> > > +		 .save_fl = native_save_fl,
> > > +		 .restore_fl = native_restore_fl,
> > > +		 .irq_disable = native_irq_disable,
> > > +		 .irq_enable = native_irq_enable,
> > > +		 .safe_halt = native_safe_halt,
> > > +		 .halt = native_halt,
> > > +	 },
> > > 
> > 
> > I think the halt stuff should be moved to pv_cpu_ops?
> > 
> You mean halt's alternate "shutdown vcpu" meaning if you call it with
> interrupts disabled?  Yeah, I'd be happy to have an explicit op for
> that, rather than making it a secondary overloaded meaning.  And use
> "safe_halt" for all uses of "wait for next interrupt".

Yes. For the native, "safe_halt" is "sti; hlt". The "native_halt" is
just "hlt". So the para_virt part of "hlt" could be moved to pv_cpu_ops,
and the "sti" part stays in pv_irq_ops.

> 
> > > +	.pv_misc_ops = {
> > > +		 .set_lazy_mode = paravirt_nop,
> > > +	 },
> > > 
> > 
> > Or you can split it to pv_cpu_ops and pv_mmu_ops, assuming that they
> > don't need to interact with each other in terms of the lazy
handling.
> > 
> 
> You mean have separate lazy_mmu and lazy_cpu (lazy_context_switch)
ops?
> Possible, but they're still exclusive.  (I think VMI, at least,
assumes
> that you can't have lazy_mmu and lazy_cpu active at the same time, and
> its nice to enforce this in the interface.)

Okay I understand what you are saying.

> 
> But having a whole misc structure for this interface is pretty warty,
I
> admit.
> 
>     J

Actually my concern was that such misc ops might grow to include the
things don't fit well anywhere else. To me, then pv_lazy_ops (with just
.set_mode) might be better.

Jun
---
Intel Open Source Technology Center
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