On Fri, Feb 12, 2021 at 12:00:15PM +0000, Lorenzo Pieralisi wrote:

On Thu, Feb 11, 2021 at 03:33:52PM +0000, Vincenzo Frascino wrote:

quoted

+void mte_suspend_enter(void)
+{
+	if (!system_supports_mte())
+		return;
+
+	/*
+	 * The barriers are required to guarantee that the indirect writes
+	 * to TFSR_EL1 are synchronized before we report the state.
+	 */
+	dsb(nsh);
+	isb();
+
+	/* Report SYS_TFSR_EL1 before suspend entry */
+	mte_check_tfsr_el1();
+}
+
 void mte_suspend_exit(void)
 {
 	if (!system_supports_mte())
 		return;
 
 	update_gcr_el1_excl(gcr_kernel_excl);
+
+	/* Clear SYS_TFSR_EL1 after suspend exit */
+	write_sysreg_s(0, SYS_TFSR_EL1);

AFAICS it is not needed, it is done already in __cpu_setup() (that is
called by cpu_resume on return from cpu_suspend() from firmware).

However, I have a question. We are relying on context switch to set
sctlr_el1_tfc0 right ? If that's the case, till the thread resuming from
low power switches context we are running with SCTLR_EL1_TCF0 not
reflecting the actual value.

I think you have a point here, though not for SCTLR_EL1 as it is already
restored. GCR_EL1 is only updated after some C code has run and may mess
up stack tagging when/if we ever support it. Anyway, something to worry
about later, I think even the boot path gets this wrong.

-- 
Catalin

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