Re: [PATCH v3 05/25] arm64: context switch POR_EL0 register

On Fri, Nov 24, 2023 at 04:34:50PM +0000, Joey Gouly wrote:

+static void flush_poe(void) +{

• if (system_supports_poe())

• write_sysreg_s(POR_EL0_INIT, SYS_POR_EL0);
  

+}

Here we have no isb()...

+static void permission_overlay_switch(struct task_struct *next) +{

• if (system_supports_poe()) {

• current->thread.por_el0 = read_sysreg_s(SYS_POR_EL0);
  

• if (current->thread.por_el0 != next->thread.por_el0) {
  

• 	write_sysreg_s(next->thread.por_el0, SYS_POR_EL0);
  

• 	isb();
  

• }
  

• }

+}

...but here we do, I'd expect them to be consistent.

If the barrier is needed it'd probably be helpful to have a comment explaining why we need it before the ERET.