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

[Juergen Gross]

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 <a...@arndb.de>

Signed-off-by: Juergen Gross <jgr...@suse.com>

Origin: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 803f4e1eab7a

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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