From mboxrd@z Thu Jan  1 00:00:00 1970
From: gerg@uclinux.org (Greg Ungerer)
Date: Thu, 9 Mar 2017 09:51:58 +1000
Subject: [PATCH v2 2/4] ARM: nommu: dynamic exception base address setting
In-Reply-To: <20170308162258.GA3515@afzalpc>
References: <314159a7-b664-1256-647d-c05880ad7710@uclinux.org>
 <20170308162258.GA3515@afzalpc>
Message-ID: <7ab1dfbd-9240-4f4b-70e2-d09ffc1039de@uclinux.org>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

Hi Afzal,

On 09/03/17 02:22, afzal mohammed wrote:
> Was standing on one leg & hoping that nothing breaks, knocked down,

I think you are still standing... Breaking an out-of-tree patch
is a bit like the tree that falls in the forest that no-one hears :-)


> On Wed, Mar 08, 2017 at 01:21:36PM +1000, Greg Ungerer wrote:
> 
>> This patch (which is in mainline now as commit f8300a0b5d) breaks
>> my patch series to support running the Versatile QEMU target with
>> a nommu configured linux kernel.
> 
> Sorry
>
>>> +	return !!cpuid_feature_extract(CPUID_EXT_PFR1, 4);
>>
>> The problem is here. This ends up generating the asm code:
>>
>>   2ebacc:       ee103f31        mrc     15, 0, r3, cr0, cr1, {1}
> 
> Thanks for finding the root cause
> 
> 
> i have in mind the diff at the end (need to recheck it's correctness),
> saw your response that Vladimir's fix works for you, either (if this
> works) way, let's fix ASAP.

The patch below works too. Thanks for the quick response.

Regards
Greg


> ---8<---
> diff --git a/arch/arm/mm/nommu.c b/arch/arm/mm/nommu.c
> index 3b5c7aaf9c76..081562f5436e 100644
> --- a/arch/arm/mm/nommu.c
> +++ b/arch/arm/mm/nommu.c
> @@ -303,7 +303,9 @@ static inline void set_vbar(unsigned long val)
>   */
>  static inline bool security_extensions_enabled(void)
>  {
> -	return !!cpuid_feature_extract(CPUID_EXT_PFR1, 4);
> +	if ((read_cpuid_id() & 0x000F0000) == 0x000F0000)
> +		return !!cpuid_feature_extract(CPUID_EXT_PFR1, 4);
> +	return 0;
>  }
>  
>  static unsigned long __init setup_vectors_base(void)
>