Why are imprecise external aborts masked on recent kernel while booting ?

[Russell King - ARM Linux]

On Fri, Jan 31, 2014 at 04:59:41PM +0100, Fabrice Gasnier wrote:
> Is it a desired change in recent kernels ?

I think it was an unnoticed behavioural change.

> Is it possible to unmask imprecise data aborts earlier in the boot  
> process (e.g. before PCIe bus enumeration, when drivers are being probed) 
> ?

How about this patch?

diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c
index 172ee18ff124..b0ff06f49cd0 100644
--- a/arch/arm/kernel/traps.c
+++ b/arch/arm/kernel/traps.c
@@ -900,6 +900,15 @@ void __init early_trap_init(void *vectors_base)
 
 	flush_icache_range(vectors, vectors + PAGE_SIZE * 2);
 	modify_domain(DOMAIN_USER, DOMAIN_CLIENT);
+
+	/* Enable imprecise aborts */
+	asm volatile(
+		"mrs	%0, cpsr\n"
+	"	bic	%0, %0, %1\n"
+	"	msr	cpsr_c, %0"
+		: "=&r" (i)
+		: "r" (PSR_A_BIT));
+
 #else /* ifndef CONFIG_CPU_V7M */
 	/*
 	 * on V7-M there is no need to copy the vector table to a dedicated


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