Re: [PATCH -v4 5/5] x86,smp: limit spinlock delay on virtual machines

[Rik van Riel]

On 01/26/2013 07:47 AM, Borislav Petkov wrote:
> On Sat, Jan 26, 2013 at 01:00:43PM +0100, Ingo Molnar wrote:
> > > +void __init init_spinlock_delay(void)
> > > +{
> > > +	if (x86_hyper)
> > > +		max_spinlock_delay = MAX_SPINLOCK_DELAY_GUEST;
> >
> > I realize that you took existing code and extended it, but that
> > chunk of code looks pretty disgusting visually now - at minimum
> > it should be vertically aligned as most other kernel code does.
> >
> > The comment should also tell that the unit of these values is
> > 'spinlock-op loops' or so.

Will do.

> Also, with currently making PARAVIRT_GUEST optional, x86_hyper is maybe
> a bad choice of a variable to test.
>
> Maybe instead to this:
>
> 	if (IS_ENABLED(CONFIG_PARAVIRT_GUEST))
> 		...

We need to know whether we are actually running on top of a
hypervisor, not whether we have the code compiled in to do
so.

After all, the majority of distribution kernels will have
CONFIG_PARAVIRT_GUEST set, but the majority of those kernels
will be running bare metal...

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