powerpc/powernv: copy/paste - Mask XERS0 bit in CR

[Michael Ellerman]

Haren Myneni <haren at linux.vnet.ibm.com> writes:
> On 06/03/2018 03:48 AM, Michael Ellerman wrote:
>> Haren Myneni <haren at linux.vnet.ibm.com> writes:
>>> NX can set 3rd bit in CR register for XER[SO] (Summation overflow)
>>> which is not related to paste request. The current paste function
>>> returns failure for the successful request when this bit is set.
>>> So mask this bit and check the proper return status.
>>>
>>> Fixes: 2392c8c8c045 ("powerpc/powernv/vas: Define copy/paste interfaces")
>>> Cc: stable at vger.kernel.org # v4.14+    
>>> Signed-off-by: Haren Myneni <haren at us.ibm.com>
>>>
>>> diff --git a/arch/powerpc/platforms/powernv/copy-paste.h b/arch/powerpc/platforms/powernv/copy-paste.h
>>> index c9a5036..82392e3 100644
>>> --- a/arch/powerpc/platforms/powernv/copy-paste.h
>>> +++ b/arch/powerpc/platforms/powernv/copy-paste.h
>>> @@ -9,7 +9,8 @@
>>>  #include <asm/ppc-opcode.h>
>>>  
>>>  #define CR0_SHIFT	28
>>> -#define CR0_MASK	0xF
>>> +#define CR0_MASK	0xE /* 3rd bit undefined or set for XER[SO] */
>>> +
>>>  /*
>>>   * Copy/paste instructions:
>>>   *
>> 
>> Unfortunately this no longer applies to my next branch, because those
>> macros have been moved out of this header as part of an unrelated patch.
>> 
>> The following patch should work instead, can you please confirm by
>> testing it?
>> 
>> diff --git a/arch/powerpc/platforms/powernv/copy-paste.h b/arch/powerpc/platforms/powernv/copy-paste.h
>> index 3fa62de96d9c..c46a326776cf 100644
>> --- a/arch/powerpc/platforms/powernv/copy-paste.h
>> +++ b/arch/powerpc/platforms/powernv/copy-paste.h
>> @@ -41,5 +41,7 @@ static inline int vas_paste(void *paste_address, int offset)
>>  		: "b" (offset), "b" (paste_address)
>>  		: "memory", "cr0");
>> 
>> -	return (cr >> CR0_SHIFT) & CR0_MASK;
>> +
>> +	/* We mask with 0xE to ignore SO */
>> +	return (cr >> CR0_SHIFT) & 0xE;
>>  }
>
> Tested with this patch and it works.

Thanks. I sent a new version to the list and will apply that.

cheers