Re: [PATCH 1/2] xen: make include/xen/unaligned.h usable on all architectures

[Juergen Gross <jgross@suse.com>]

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On 05.12.23 12:53, Julien Grall wrote:
> Hi Juergen,
> 
> On 05/12/2023 10:07, Juergen Gross wrote:
>> Instead of defining get_unaligned() and put_unaligned() in a way that
>> is only supporting architectures allowing unaligned accesses, use the
>> same approach as the Linux kernel and let the compiler do the
>> decision how to generate the code for probably unaligned data accesses.
>>
>> Update include/xen/unaligned.h from include/asm-generic/unaligned.h of
>> the Linux kernel.
>>
>> The generated code has been checked to be the same on x86.
>>
>> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
>> Origin: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 
>> 803f4e1eab7a
>> Signed-off-by: Juergen Gross <jgross@suse.com>
> 
> Can you outline your end goal? At least on arm32, I believe this will result to 
> abort because event if the architecture support unaligned access, we are 
> preventing them on Arm32.

I need something like that in Xen tools for supporting packed data accesses
on the 9pfs ring page, so I looked into the hypervisor for related support.

I guess for arm32 using -mno-unaligned-access when building should avoid any
unaligned accesses?


Juergen

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