Re: [Xen-devel] [PATCH] xen: arm: bitops take unsigned int (Was: Re: [PATCH] xen/arm64: disable alignment check)

[Julien Grall <julien.grall@xxxxxxxxxx>]

Hi Ian,

On 05/09/2014 05:19 PM, Ian Campbell wrote:
> (Just adding the other ARM guys...)
> 
> On Fri, 2014-05-09 at 14:24 +0100, Ian Campbell wrote:
>> On Tue, 2014-04-29 at 09:58 +0100, Ian Campbell wrote:
>>> On Tue, 2014-04-29 at 08:38 +0100, Vladimir Murzin wrote:
>>>> On Mon, Apr 28, 2014 at 11:43 AM, Ian Campbell <Ian.Campbell@xxxxxxxxxx> 
>>>> wrote:
>>>>> But I also wanted confirmation that the problematic instruction was
>>>>> generated by gcc and not by some handcoded asm somewhere which we hadn't
>>>>> properly fixed.
>>>
>>>> I believe it comes form test_bit (xen/include/asm-arm/bitops.h).
>>>
>>> Ah, then I think this code needs fixing too. Probably switching to
>>> unsigned int * throughout would work, what do you think?
>>
>> I finally managed to upgrade to a new enough kernel to trigger this.
>>
>> This Works For Me(tm), along with the Linux patch "xen/events/fifo:
>> correctly align bitops" which is queued for 3.15 Linus (but not sent
>> yet?)
>>
>> 8<-------------------
>>
>> From aa6afe6520ea22241fb0ce430ef315c49a73867f Mon Sep 17 00:00:00 2001
>> From: Ian Campbell <ian.campbell@xxxxxxxxxx>
>> Date: Thu, 8 May 2014 16:13:55 +0100
>> Subject: [PATCH] xen: arm: bitops take unsigned int
>>
>> Xen bitmaps can be 4 rather than 8 byte aligned, so use the appropriate type.
>> Otherwise the compiler can generate unaligned 8 byte accesses and cause 
>> traps.
>>
>> Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
>> ---
>>  xen/include/asm-arm/bitops.h |   37 +++++++++++++++++++------------------
>>  1 file changed, 19 insertions(+), 18 deletions(-)
>>
>> diff --git a/xen/include/asm-arm/bitops.h b/xen/include/asm-arm/bitops.h
>> index 0a7caee..25f96c8 100644
>> --- a/xen/include/asm-arm/bitops.h
>> +++ b/xen/include/asm-arm/bitops.h
>> @@ -18,13 +18,14 @@
>>  #define __set_bit(n,p)            set_bit(n,p)
>>  #define __clear_bit(n,p)          clear_bit(n,p)
>>  
>> +#define BITS_PER_WORD           32

Can you define BITS_PER_WORD in asm-arm/config.h rather than here?

Regards,

-- 
Julien Grall

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