Re: [Xen-devel] [PATCH v2 05/19] xen: arm: Add and use r/o+raz and w/o+wi helpers

[Julien Grall <julien.grall@xxxxxxxxxx>]

Hi Ian,

On 17/04/2015 19:01, Ian Campbell wrote:
> Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
> ---
> v2: Move last paramter of a handle_ro_raz call to next patch where it
>      belongs.
> ---
>   xen/arch/arm/traps.c |   52 ++++++++++++++++++++++++++++++++------------------
>   1 file changed, 33 insertions(+), 19 deletions(-)
>
> diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c
> index 8b1846a..b54aef6 100644
> --- a/xen/arch/arm/traps.c
> +++ b/xen/arch/arm/traps.c
> @@ -1587,6 +1587,34 @@ static void handle_raz_wi(struct cpu_user_regs *regs,
>       advance_pc(regs, hsr);
>   }
>
> +/* Write only + write ignore */
[..]

> +/* Read only + read as zero */
I'm not sure if we finished the discussion on those comment on v1 before 
you sent the v2.
The "+" is very confusing for me because it indicates two parts: write 
only and write ignore (same for the read). Both part doesn't really fit 
together. Although this helper clearly choose to implement WO as WI 
(resp. RO as RAZ).
I think this should be clearer in order to avoid people think this can 
be used for RO but with a different value than 0.
Regards,

--
Julien Grall

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