On Thu, 2023-06-08 at 06:43 -0700, Dave Hansen wrote:
> On 6/7/23 19:10, Huang, Kai wrote:
> > On Wed, 2023-06-07 at 08:22 -0700, Dave Hansen wrote:
> > > On 6/4/23 07:27, Kai Huang wrote:
> > > ...
> > > > +static int try_init_module_global(void)
> > > > +{
> > > > + unsigned long flags;
> > > > + int ret;
> > > > +
> > > > + /*
> > > > + * The TDX module global initialization only needs to be done
> > > > + * once on any cpu.
> > > > + */
> > > > + raw_spin_lock_irqsave(&tdx_global_init_lock, flags);
> > >
> > > Why is this "raw_"?
> > >
> > > There's zero mention of it anywhere.
> >
> > Isaku pointed out the normal spinlock_t is converted to sleeping lock for
> > PREEMPT_RT kernel. KVM calls this with IRQ disabled, thus requires a non-
> > sleeping lock.
> >
> > How about adding below comment here?
> >
> > /*
> > * Normal spinlock_t is converted to sleeping lock in PREEMPT_RT
> > * kernel. Use raw_spinlock_t instead so this function can be called
> > * even when IRQ is disabled in any kernel configuration.
> > */
>
> Go look at *EVERY* *OTHER* raw_spinlock_t in the kernel. Do any of them
> say this?
>
> Comment the function, say that it's always called with interrupts and
> preempt disabled. Leaves it at that. *Maybe* add on that it needs raw
> spinlocks because of it. But don't (try to) explain the background of
> the lock type.
>
Thanks. Will do, with one minor:
I'd like to replace "it's always called with interrupts and preempt disabled"
with "it can be called with interrupts disabled", because in the future non-KVM
code may call this when interrupt is enabled but preemption is disabled.
[...]
> > > > +EXPORT_SYMBOL_GPL(tdx_cpu_enable);
> > >
> > > You danced around it in the changelog, but the reason for the exports is
> > > not clear.
> >
> > I'll add one sentence to the changelog to explain:
> >
> > Export both tdx_cpu_enable() and tdx_enable() as KVM will be the kernel
> > component to use TDX.
>
> Intel doesn't pay me by the word. Do you get paid that way? If not,
> please just say:
>
> Export both tdx_cpu_enable() and tdx_enable() for KVM use.
Thanks!
