Re: [PATCH] locking/x86/xen: Use try_cmpxchg() in xen_alloc_p2m_entry()

[Jürgen Groß]

On 05.04.24 10:32, Uros Bizjak wrote:
> Use try_cmpxchg() instead of cmpxchg(*ptr, old, new) == old.
>
> The x86 CMPXCHG instruction returns success in the ZF flag,
> so this change saves a compare after CMPXCHG.
>
> Also, try_cmpxchg() implicitly assigns old *ptr value to "old"
> when CMPXCHG fails. There is no need to explicitly assign
> old *ptr value to the temporary, which can simplify the
> surrounding source code.
>
> No functional change intended.
>
> Signed-off-by: Uros Bizjak <ubizjak@xxxxxxxxx>
> Cc: Juergen Gross <jgross@xxxxxxxx>
> Cc: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Cc: Ingo Molnar <mingo@xxxxxxxxxx>
> Cc: Borislav Petkov <bp@xxxxxxxxx>
> Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
> Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>

Reviewed-by: Juergen Gross <jgross@xxxxxxxx>


Juergen