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Re: [PATCH v2 2/3] xen: make include/xen/unaligned.h usable on all architectures
- To: Juergen Gross <jgross@xxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Wed, 6 Dec 2023 09:46:49 +0100
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- Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, George Dunlap <george.dunlap@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, Arnd Bergmann <arnd@xxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx
- Delivery-date: Wed, 06 Dec 2023 08:46:59 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 06.12.2023 08:10, 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.
>
> Modify the Linux variant to not use underscore prefixed identifiers,
> avoid unneeded parentheses and drop the 24-bit accessors.
>
> Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
> Origin: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
> 803f4e1eab7a
> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
Nevertheless ...
> @@ -15,67 +7,82 @@
> #include <asm/byteorder.h>
> #endif
>
> -#define get_unaligned(p) (*(p))
> -#define put_unaligned(val, p) (*(p) = (val))
> +/*
> + * This is the most generic implementation of unaligned accesses
> + * and should work almost anywhere.
> + */
> +
> +#define get_unaligned_t_(type, ptr) ({
> \
..., do we need the trailing underscores here in addition to the already
sufficiently clear _t suffixes? (Leaving aside that ..._t generally is to
denote types, not macros or functions.)
Jan
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