Re: [PATCH v5 09/22] x86/virt/seamldr: Introduce skeleton for TDX module updates

[Chao Gao]

>> +static struct {
>> +	enum module_update_state state;
>> +	int thread_ack;
>> +	/*
>> +	 * Protect update_data. Raw spinlock as it will be acquired from
>> +	 * interrupt-disabled contexts.
>> +	 */
>> +	raw_spinlock_t lock;
>> +} update_data = {
>> +	.lock = __RAW_SPIN_LOCK_UNLOCKED(update_data.lock)
>> +};
>
>multi_stop_cpu() used atomic_t for thread_ack insead of spinlock.
>Any particular reason you took different direction?

I switched from atomic_t to spinlock in v5 after Dave complained [*] that using
atomic_t and memory barriers is "overly complicated".

Testing both approaches showed no scalability issues, so I chose spinlock for
better readability.

*: https://lore.kernel.org/kvm/abP%2F2nPh9qkElV4L@xxxxxxxxx/