Re: [PATCH 8/8] membarrier: Rewrite sync_core_before_usermode() and improve documentation

On 6/15/21 9:45 PM, Nicholas Piggin wrote:

Excerpts from Andy Lutomirski's message of June 16, 2021 1:21 pm:

...

The old sync_core_before_usermode() comments suggested that a non-icache-syncing return-to-usermode instruction is x86-specific and that all other architectures automatically notice cross-modified code on return to userspace.

...

+/*

• • XXX: can a powerpc person put an appropriate comment here?
• */

+static inline void membarrier_sync_core_before_usermode(void) +{ +}

+#endif /* _ASM_POWERPC_SYNC_CORE_H */

powerpc's can just go in asm/membarrier.h

$ ls arch/powerpc/include/asm/membarrier.h ls: cannot access 'arch/powerpc/include/asm/membarrier.h': No such file or directory

/*

• The RFI family of instructions are context synchronising, and
• that is how we return to userspace, so nothing is required here.

*/

Thanks!