Re: [PATCH v12 07/22] x86/virt/tdx: Add skeleton to enable TDX on demand

[kirill.shutemov@xxxxxxxxxxxxxxx]

On Wed, Jun 28, 2023 at 12:28:12AM +0000, Huang, Kai wrote:
> On Tue, 2023-06-27 at 22:37 +0000, Huang, Kai wrote:
> > > > 
> > > > +/*
> > > > + * Do the module global initialization if not done yet.
> > > > + * It's always called with interrupts and preemption disabled.
> > > > + */
> > > 
> > > If interrupts are always disabled why do you need _irqsave()?
> > > 
> > 
> > I'll remove the _irqsave().
> > 
> > AFAICT Isaku preferred this for additional security, but this is not
> > necessary.
> > 
> > 
> 
> Damn.  I think we can change the comment to say this function is called with
> preemption being disabled, but _can_ be called with interrupt disabled.  And we
> keep using the _irqsave() version.
> 
> 	/*
> 	 * Do the module global initialization if not done yet.  It's always
> 	 * called with preemption disabled and can be called with interrupts
> 	 * disabled.
> 	 */
> 
> This allows a use case that the caller simply wants to call some SEAMCALL on
> local cpu, e.g., IOMMU code may just use below to get some TDX-IO information:
> 
> 	preempt_disable();
> 	vmxon();
> 	tdx_cpu_enable();
> 	SEAMCALL;
> 	vmxoff();
> 	preempt_enable();
> 
> Are you OK with this?

Is it hypothetical use-case? If so, I would rather keep it simple for now
and adjust in the future if needed.

-- 
  Kiryl Shutsemau / Kirill A. Shutemov