Re: [Xen-devel] [PATCH 4/9] xen/arm: traps: Simplify the switch in do_trap_*_abort_guest

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Wed, 22 Jun 2016, Julien Grall wrote:
> The fault status we care are all the form BBBBxx where xx is the lookup

                                 ^ in the form of

> level that gave the fault. We can simply the code by masking the 2 least

                                       ^ simplify

> significant bits.
> 
> Signed-off-by: Julien Grall <julien.grall@xxxxxxx>
> ---
>  xen/arch/arm/traps.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c
> index 2e84b5a..8a3fac0 100644
> --- a/xen/arch/arm/traps.c
> +++ b/xen/arch/arm/traps.c
> @@ -2388,9 +2388,9 @@ static void do_trap_instr_abort_guest(struct 
> cpu_user_regs *regs,
>      int rc;
>      register_t gva = READ_SYSREG(FAR_EL2);
>  
> -    switch ( hsr.iabt.ifsc & 0x3f )
> +    switch ( hsr.iabt.ifsc & ~FSC_LL_MASK )
>      {
> -    case FSC_FLT_PERM ... FSC_FLT_PERM + 3:
> +    case FSC_FLT_PERM:
>      {

This is a good improvement in code readability. I would go one step
further and replace the switch with a simple if.


>          paddr_t gpa;
>          const struct npfec npfec = {
> @@ -2451,9 +2451,9 @@ static void do_trap_data_abort_guest(struct 
> cpu_user_regs *regs,
>              return; /* Try again */
>      }
>  
> -    switch ( dabt.dfsc & 0x3f )
> +    switch ( dabt.dfsc & ~FSC_LL_MASK )
>      {
> -    case FSC_FLT_PERM ... FSC_FLT_PERM + 3:
> +    case FSC_FLT_PERM:
>      {
>          const struct npfec npfec = {
>              .read_access = !dabt.write,

same here


> -- 
> 1.9.1
> 

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