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Message-ID: <bea651c0-9184-79ea-5613-c59fa6c64a79@arm.com>
Date: Fri, 26 Jan 2018 12:21:43 +0000
From: Suzuki K Poulose <Suzuki.Poulose@....com>
To: Dave Martin <Dave.Martin@....com>
Cc: linux-arm-kernel@...ts.infradead.org, mark.rutland@....com,
ckadabi@...eaurora.org, ard.biesheuvel@...aro.org,
marc.zyngier@....com, catalin.marinas@....com, will.deacon@....com,
linux-kernel@...r.kernel.org, jnair@...iumnetworks.com
Subject: Re: [PATCH 07/16] arm64: capabilities: Filter the entries based on a
given type
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@....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
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