Re: [PATCH 07/16] arm64: capabilities: Filter the entries based on a given type

[Suzuki K Poulose <Suzuki.Poulose@arm.com>]

On 26/01/18 11:22, Dave Martin wrote:
> On Tue, Jan 23, 2018 at 12:28:00PM +0000, Suzuki K Poulose wrote:
>> While processing the list of capabilities, it is useful to
>> filter out some of the entries based on the given type to
>> allow better control. This can be used later for handling
>> LOCAL vs SYSTEM wide capabilities and more.
>>
>> Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
>> ---
>>   arch/arm64/include/asm/cpufeature.h |  5 +++++
>>   arch/arm64/kernel/cpufeature.c      | 30 ++++++++++++++++++++----------
>>   2 files changed, 25 insertions(+), 10 deletions(-)
>>
>> diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
>> index 27d037bb0451..a621d2184227 100644
>> --- a/arch/arm64/include/asm/cpufeature.h
>> +++ b/arch/arm64/include/asm/cpufeature.h
>> @@ -99,6 +99,11 @@ extern struct arm64_ftr_reg arm64_ftr_reg_ctrel0;
>>   /* Is it safe for a late CPU to miss this capability when system has it */
>>   #define ARM64_CPUCAP_LATE_CPU_SAFE_TO_MISS	BIT(3)
>>   
>> +#define ARM64_CPUCAP_TYPE_ALL			 \
>> +	(ARM64_CPUCAP_SCOPE_LOCAL_CPU		|\
>> +	 ARM64_CPUCAP_SCOPE_SYSTEM		|\
>> +	 ARM64_CPUCAP_LATE_CPU_SAFE_TO_HAVE	|\
>> +	 ARM64_CPUCAP_LATE_CPU_SAFE_TO_MISS)
> 
> Nit: can we have another tab between | and \?
> 
> This will help to make missing |s stand out more if/when more entries
> are added to this list in future.
> 

Sure, will do.

>>   /*
>>    * CPU errata detected at boot time based on feature of one or more CPUs.
>>    * It is not safe for a late CPU to have this feature when the system doesn't
>> diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
>> index 79737034a628..198c5daddd65 100644
>> --- a/arch/arm64/kernel/cpufeature.c
>> +++ b/arch/arm64/kernel/cpufeature.c
>> @@ -1180,9 +1180,11 @@ static bool __this_cpu_has_cap(const struct arm64_cpu_capabilities *cap_array,
>>   }
>>   
>>   static void update_cpu_capabilities(const struct arm64_cpu_capabilities *caps,
>> -			    const char *info)
>> +				    u16 cap_type, const char *info)
> 
> Semantically "cap_type" represents a set of accepted types, not a single
> type here.
> 
> Can we rename it to "cap_types", "cap_type_mask" or similar?
> 
>>   {
>>   	for (; caps->matches; caps++) {
>> +		if (!(caps->type & cap_type))
>> +			continue;
> 
> Minor nit: insert a blank line here?
> 
> To me, lack of a blank line suggests that the code will always fall
> through to the next line, which is not the case after
> return/continue/break/goto.
> 
> Alternatively:
> 
> 		if (!(caps->type & cap_type) ||
> 		    !caps->matches(caps, caps->def_scope))
> 			continue;
> 
> still seems fairly intelligible ...[1]
> 
>>   		if (!caps->matches(caps, cpucap_default_scope(caps)))
>>   			continue;
>>   

Yep, will do.

>> @@ -1204,12 +1206,13 @@ static int __enable_cpu_capability(void *arg)
>>    * Run through the enabled capabilities and enable() it on all active
>>    * CPUs
>>    */
>> -static void __init enable_cpu_capabilities(const struct arm64_cpu_capabilities *caps)
>> +static void __init
>> +enable_cpu_capabilities(const struct arm64_cpu_capabilities *caps, u16 caps_type)
> 
> The "caps_type" argument should be named consistently with the
> corresponding argument to update_cpu_capabilities().
> 
>>   {
>>   	for (; caps->matches; caps++) {
>>   		unsigned int num = caps->capability;
>>   
>> -		if (!cpus_have_cap(num))
>> +		if (!(caps->type & caps_type) || !cpus_have_cap(num))
> 
> [1]... and would match the approach taken here.
> 
>>   			continue;
>>   
>>   		/* Ensure cpus_have_const_cap(num) works */
>> @@ -1231,12 +1234,16 @@ static void __init enable_cpu_capabilities(const struct arm64_cpu_capabilities *
>>    * Run through the list of capabilities to check for conflicts.
>>    * Returns "false" on conflicts.
>>    */
>> -static bool __verify_local_cpu_caps(const struct arm64_cpu_capabilities *caps_list)
>> +static bool __verify_local_cpu_caps(const struct arm64_cpu_capabilities *caps_list,
>> +				    u16 caps_type)
>>   {
>>   	bool cpu_has_cap, system_has_cap;
>>   	const struct arm64_cpu_capabilities *caps = caps_list;
>>   
>>   	for (; caps->matches; caps++) {
>> +		if (!(caps->type & caps_type))
>> +			continue;
>> +
>>   		cpu_has_cap = __this_cpu_has_cap(caps_list, caps->capability);
>>   		system_has_cap =  cpus_have_cap(caps->capability);
>>   
>> @@ -1299,7 +1306,7 @@ verify_local_elf_hwcaps(const struct arm64_cpu_capabilities *caps)
>>   
>>   static void verify_local_cpu_features(void)
>>   {
>> -	if (!__verify_local_cpu_caps(arm64_features))
>> +	if (!__verify_local_cpu_caps(arm64_features, ARM64_CPUCAP_TYPE_ALL))
>>   		cpu_die_early();
>>   }
>>   
>> @@ -1327,18 +1334,20 @@ static void verify_sve_features(void)
>>    */
>>   static void verify_local_cpu_errata_workarounds(void)
>>   {
>> -	if (__verify_local_cpu_caps(arm64_errata))
>> +	if (!__verify_local_cpu_caps(arm64_errata, ARM64_CPUCAP_TYPE_ALL))
>>   		cpu_die_early();
> 
> Did you mean to insert the ! here?

Thanks for spotting. I think it should have been there in the first place,
as we get "false" when there is a conflict. I will fix the previous patch which
adds the call.

Cheers
Suzuki