[RFC PATCH v2 06/45] arm64: suspend: Initialize PMR on resume

[Vladimir Murzin]

When we resume from cpu_suspend() context tracking, specially,
ct_idle_exit() performs IRQ save/restore sequence. It doesn't cause
any functional issues since we have masked all exceptions prior
suspend and have not restored them. However, in case of pseudo-NMI PMR
can be set by firmware to arbitrary value, thus IRQ save/restore
routines manipulates this arbitrary value. Again, it doesn't cause any
issues since PMR variant of IRQ save helper carries a
__pmr_irqs_disabled_flags() guard.

Going forward __pmr_irqs_disabled_flags() guard will be gone and we
will call __pmr_local_irq_disable() unconditionally - that would cause
warning in case CONFIG_ARM64_DEBUG_PRIORITY_MASKING is set.

Initialize PMR to a value known to Linux on resume until the normal
exception restore path restores the saved DAIF and PMR state.

Signed-off-by: Vladimir Murzin <vladimir.murzin at arm.com>
---
 arch/arm64/mm/proc.S | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S
index 22866b49be37..06c8bc9a85d6 100644
--- a/arch/arm64/mm/proc.S
+++ b/arch/arm64/mm/proc.S
@@ -169,6 +169,13 @@ alternative_if ARM64_HAS_RAS_EXTN
 	msr_s	SYS_DISR_EL1, xzr
 alternative_else_nop_endif
 
+#ifdef CONFIG_ARM64_PSEUDO_NMI
+alternative_if ARM64_HAS_GIC_PRIO_MASKING
+	mov	x1, #GIC_PRIO_IRQON
+	msr_s	SYS_ICC_PMR_EL1, x1
+alternative_else_nop_endif
+#endif
+
 	ptrauth_keys_install_kernel_nosync x14, x1, x2, x3
 	isb
 	ret
-- 
2.34.1