Re: [Xen-devel] [PATCH 08/18] xen/arm: Introduce a initcall to update cpu_hwcaps by serror_op

[Wei Chen <Wei.Chen@xxxxxxx>]

Hi Stefano,

On 2017/3/17 7:30, Stefano Stabellini wrote:
> On Mon, 13 Mar 2017, Wei Chen wrote:
>> In the later patches of this series, we want to use the alternative
>> patching framework to avoid checking serror_op in every entries.
>> So we define a new cpu feature "SKIP_CHECK_PENDING_VSERROR" for
>> serror_op. When serror_op is not equal to SERROR_DIVERSE, this
>> feature will be set to cpu_hwcaps.
>>
>> But we could not update cpu_hwcaps directly in the serror parameter
>> parsing function. Because if the serror parameter is not placed in
>> the command line, the parsing function would not be invoked.
>
> Wait, the only way to set serrors_op != SERRORS_DIVERSE is to pass the
> "serror" command line parameter. The parsing function is always invoked
> if serrors_op != SERRORS_DIVERSE.
>

Yes, but that because we set serrors_op to SERRORS_DIVERSE by default.
If we change the policy and set serrors_op to SERRORS_PANIC by default, 
then the parsing function would never be invoked.

>
>> So, we introduce this initcall to guarantee the cpu_hwcaps can be
>> updated no matter the serror parameter is placed in the command line
>> or not.
>>
>> Signed-off-by: Wei Chen <Wei.Chen@xxxxxxx>
>> ---
>>  xen/arch/arm/traps.c             | 9 +++++++++
>>  xen/include/asm-arm/cpufeature.h | 3 ++-
>>  2 files changed, 11 insertions(+), 1 deletion(-)
>>
>> diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c
>> index 5e31699..053b7fc 100644
>> --- a/xen/arch/arm/traps.c
>> +++ b/xen/arch/arm/traps.c
>> @@ -134,6 +134,15 @@ static void __init parse_serrors_behavior(const char 
>> *str)
>>  }
>>  custom_param("serrors", parse_serrors_behavior);
>>
>> +static __init int update_serrors_cpu_caps(void)
>
> I think the coding style is "static int __init" ...
>

Oh, thanks, I will fix it.

>
>> +{
>> +    if ( serrors_op != SERRORS_DIVERSE )
>> +        cpus_set_cap(SKIP_CHECK_PENDING_VSERROR);
>> +
>> +    return 0;
>> +}
>> +__initcall(update_serrors_cpu_caps);
>> +
>>  register_t get_default_hcr_flags(void)
>>  {
>>      return  (HCR_PTW|HCR_BSU_INNER|HCR_AMO|HCR_IMO|HCR_FMO|HCR_VM|
>> diff --git a/xen/include/asm-arm/cpufeature.h 
>> b/xen/include/asm-arm/cpufeature.h
>> index c0a25ae..ec3f9e5 100644
>> --- a/xen/include/asm-arm/cpufeature.h
>> +++ b/xen/include/asm-arm/cpufeature.h
>> @@ -40,8 +40,9 @@
>>  #define ARM32_WORKAROUND_766422 2
>>  #define ARM64_WORKAROUND_834220 3
>>  #define LIVEPATCH_FEATURE   4
>> +#define SKIP_CHECK_PENDING_VSERROR 5
>>
>> -#define ARM_NCAPS           5
>> +#define ARM_NCAPS           6
>>
>>  #ifndef __ASSEMBLY__
>>
>> --
>> 2.7.4
>>
>>
>> _______________________________________________
>> Xen-devel mailing list
>> Xen-devel@xxxxxxxxxxxxx
>> https://lists.xen.org/xen-devel
>>
>


-- 
Regards,
Wei Chen

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