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SubjectRe: [PATCH v12 19/22] x86/kexec(): Reset TDX private memory on platforms with TDX erratum
On Tue, Jun 27, 2023 at 02:12:49AM +1200, Kai Huang wrote:
> @@ -1113,6 +1115,17 @@ static int init_tdx_module(void)
> */
> wbinvd_on_all_cpus();
>
> + /*
> + * Starting from this point the system may have TDX private
> + * memory. Make it globally visible so tdx_reset_memory() only
> + * reads TDMRs/PAMTs when they are stable.
> + *
> + * Note using atomic_inc_return() to provide the explicit memory
> + * ordering isn't mandatory here as the WBINVD above already
> + * does that. Compiler barrier isn't needed here either.
> + */
> + atomic_inc_return(&tdx_may_has_private_mem);

Why do we need atomics at all here? Writers seems serialized with
tdx_module_lock and reader accesses the variable when all CPUs, but one is
down and cannot race.

Hm?

--
Kiryl Shutsemau / Kirill A. Shutemov

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