linux-kernel - Re: [PATCH] ARM: keystone: add a work around to handle asynchronous external abort

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Date:	Fri, 14 Aug 2015 16:20:59 +0200
From:	Lucas Stach <l.stach@...gutronix.de>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
Cc:	Murali Karicheri <m-karicheri2@...com>,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	ssantosh@...nel.org
Subject: Re: [PATCH] ARM: keystone: add a work around to handle asynchronous
 external abort

Hi Russell,

Am Freitag, den 14.08.2015, 15:09 +0100 schrieb Russell King - ARM
Linux:

[...]

> 
> What causes the abort?  We shouldn't be adding hacks like this to the
> kernel without having the full picture...
> 

some of the issues with tracking down such imprecise external aborts are
due to the fact that we only enable the signaling of those aborts on
entering the user-space. So the first schedule() crashes on the previous
dangling abort.

I'm carrying this patch locally to enable imprecise aborts much earlier
in the boot process. I think it has already been on the list some times,
but apparently it has fallen through the cracks. If you agree that this
is the right thing to do I can do a proper repost.

Regards,
Lucas

---------------------->8---------------------------------------------
>From bb9117d94cc2f1061dc364f42c446ccd9191e869 Mon Sep 17 00:00:00 2001
From: Lucas Stach <l.stach@...gutronix.de>
Date: Thu, 19 Feb 2015 18:12:50 +0100
Subject: [PATCH] ARM: Add imprecise abort enable/disable macro

This patch adds imprecise abort enable/disable macros.
It also enables imprecise aborts when starting kernel.

Changes in v2:
Only ARMv6 and later have CPSR.A bit. On earlier CPUs,
and ARMv7M this should be a no-op.

Signed-off-by: Fabrice Gasnier <fabrice.gasnier@...com>
Signed-off-by: Lucas Stach <l.stach@...gutronix.de>
---
lst: rebased on v3.19
---
 arch/arm/include/asm/irqflags.h | 10 ++++++++++
 arch/arm/kernel/smp.c           |  1 +
 arch/arm/kernel/traps.c         |  4 ++++
 3 files changed, 15 insertions(+)

diff --git a/arch/arm/include/asm/irqflags.h
b/arch/arm/include/asm/irqflags.h
index 3b763d6652a0..8301f875564e 100644
--- a/arch/arm/include/asm/irqflags.h
+++ b/arch/arm/include/asm/irqflags.h
@@ -51,6 +51,14 @@ static inline void arch_local_irq_disable(void)
 
 #define local_fiq_enable()  __asm__("cpsie f   @ __stf" : : : "memory",
"cc")
 #define local_fiq_disable() __asm__("cpsid f   @ __clf" : : : "memory",
"cc")
+
+#ifndef CONFIG_CPU_V7M
+#define local_abt_enable()  __asm__("cpsie a   @ __sta" : : : "memory",
"cc")
+#define local_abt_disable() __asm__("cpsid a   @ __cla" : : : "memory",
"cc")
+#else
+#define local_abt_enable()     do { } while (0)
+#define local_abt_disable()    do { } while (0)
+#endif
 #else
 
 /*
@@ -130,6 +138,8 @@ static inline void arch_local_irq_disable(void)
        : "memory", "cc");                                      \
        })
 
+#define local_abt_enable()     do { } while (0)
+#define local_abt_disable()    do { } while (0)
 #endif
 
 /*
diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c
index 86ef244c5a24..7b6b93cabef4 100644
--- a/arch/arm/kernel/smp.c
+++ b/arch/arm/kernel/smp.c
@@ -378,6 +378,7 @@ asmlinkage void secondary_start_kernel(void)
 
        local_irq_enable();
        local_fiq_enable();
+       local_abt_enable();
 
        /*
         * OK, it's off to the idle thread for us
diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c
index 788e23fe64d8..466726ba9bdb 100644
--- a/arch/arm/kernel/traps.c
+++ b/arch/arm/kernel/traps.c
@@ -881,6 +881,10 @@ 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 */
+       local_abt_enable();
+
 #else /* ifndef CONFIG_CPU_V7M */
        /*
         * on V7-M there is no need to copy the vector table to a
dedicated
-- 
2.1.4

-- 
Pengutronix e.K.             | Lucas Stach                 |
Industrial Linux Solutions   | http://www.pengutronix.de/  |

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