Re: [Xen-devel] [PATCH v2 1/4] arm: processor: rename iss to res0 in hsr_cond union

[Julien Grall <julien.grall@xxxxxxx>]

Hi Volodymyr,

On 09/08/2017 20:44, Volodymyr Babchuk wrote:
> Name "iss" in this case was used not exactly correctly, because this
> is only part of HSR.ISS field. ARM refence manual denotes this
> part of ISS as RES0 when it describes encoding for conditional
> exceptions (ARM DDI 0487A.k pages D7-1939 - D7-1949).   
Please use the latest ARM manual (i.e ARM DDI 0487A.b). And this is 
still not true. If you look at:
        - WFI/WFE, bit 1 is not res0.
        - MCR/MRC, all bits are defined

If you really want to rename this field, then name it pad or ign. But 
res0 is completely bogus.
Cheers,

> Signed-off-by: Volodymyr Babchuk <volodymyr_babchuk@xxxxxxxx>
> ---
>
> - Added reference to ARM archtecture manual in the commit message.
>
> ---
>  xen/include/asm-arm/processor.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/xen/include/asm-arm/processor.h b/xen/include/asm-arm/processor.h
> index 855ded1..f640d54 100644
> --- a/xen/include/asm-arm/processor.h
> +++ b/xen/include/asm-arm/processor.h
> @@ -434,7 +434,7 @@ union hsr {
>
>      /* Common to all conditional exception classes (0x0N, except 0x00). */
>      struct hsr_cond {
> -        unsigned long iss:20;  /* Instruction Specific Syndrome */
> +        unsigned long res0:20;  /* Reserved */
>          unsigned long cc:4;    /* Condition Code */
>          unsigned long ccvalid:1;/* CC Valid */
>          unsigned long len:1;   /* Instruction length */
--
Julien Grall

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