Re: [Xen-devel] [PATCH 2/2] xen/arm: support compressed kernels

[Julien Grall <julien.grall@xxxxxxxxxx>]

On 12/08/15 16:22, Stefano Stabellini wrote:
>>>  obj-$(perfc)       += perfc.o
>>>  obj-$(crash_debug) += gdbstub.o
>>> diff --git a/xen/include/asm-arm/byteorder.h b/xen/include/asm
>>> -arm/byteorder.h
>>> index 9c712c4..3b7feda 100644
>>> --- a/xen/include/asm-arm/byteorder.h
>>> +++ b/xen/include/asm-arm/byteorder.h
>>> @@ -5,6 +5,8 @@
>>>  
>>>  #include <xen/byteorder/little_endian.h>
>>>  
>>> +#define CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
>>
>> While CONFIG_HAVE_UNALIGNED_ACCESS might be true on arm64 it may not be the
>> case that it is efficient. Also I'm not sure about arm32 at all.
> 
> It is true on arm archs >= v8, so we should be fine. See:

I guess you meant v6?

Although, unaligned access are not allowed in Xen on ARM32. See
arm32/head.S:353

Given that the uncompress code is only used for decompressing DOM0
kernel, I don't think it's worth to enable unaligned access.

Regards,

-- 
Julien Grall

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