Re: [PATCH v11 18/20] x86: Handle TDX erratum to reset TDX private memory during kexec() and reboot

[Dave Hansen]

On 6/19/23 04:43, Huang, Kai wrote:
> On Mon, 2023-06-12 at 06:47 -0700, Dave Hansen wrote:
>> On 6/12/23 03:27, Huang, Kai wrote:
>>> So I think a __mb() after setting tdmr->pamt_4k_base should be good enough, as
>>> it guarantees when setting to any pamt_*_size happens, the valid pamt_4k_base
>>> will be seen by other cpus.
>>>
>>> Does it make sense?
>> Just use a normal old atomic_t or set_bit()/test_bit().  They have
>> built-in memory barriers are are less likely to get botched.
> Hi Dave,
> 
> Using atomic_set() requires changing tdmr->pamt_4k_base to atomic_t, which is a
> little bit silly or overkill IMHO.  Looking at the code, it seems
> arch_atomic_set() simply uses __WRITE_ONCE():

How about _adding_ a variable that protects tdmr->pamt_4k_base?
Wouldn't that be more straightforward than mucking around with existing
types?