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

[Peter Zijlstra]

On Thu, Jun 29, 2023 at 12:00:44AM +0000, Huang, Kai wrote:

> The spec says it doesn't have a latency requirement, so theoretically it could
> be long.  SEAMCALL is a VMEXIT so it would at least cost thousands of cycles.

:-(

> If raw_spinlock isn't desired, I think I can introduce another function to do
> this and let the caller to call it before calling tdx_cpu_enable().  E.g., we
> can have below functions:
> 
> 1) tdx_global_init()	-> TDH_SYS_INIT
> 2) tdx_cpu_init()	-> TDH_SYS_LP_INIT
> 3) tdx_enable()		-> actual module initialization
> 
> How does this sound?

Ah, wait, I hadn't had enough wake-up juice, it's tdx_global_init() that
did the raw_spinlock_t, but that isn't the IPI thing.

Then perhaps just use a mutex to serialize things?