[PATCH 0/7] arm64: capabilities: Optimize checking and enabling

Vladimir Murzin
2018-11-05T12:14:16Z

Hi Suzuki,

On 05/11/18 11:55, Suzuki K Poulose wrote:
> We maintain two separate tables (i.e, arm64_features and arm64_errata) of
> struct arm64_cpu_capabilities which decide the capabilities of the system.
> We iterate over the two tables for detecting/verifying/enabling the capabilities.
> e.g, this_cpu_has_cap() needs to iterate over the two tables one by one to
> find the "capability" structure corresponding to the cap number and then
> check it on the CPU.
>
> Also, we enable all the non-boot scoped capabilities after all the SMP cpus
> are brought up by the kernel, using stop_machine() for each available
> capability. We could batch all the "enabling" activity to a single
> stop_machine() callback. But that implies you need a way to map
> a given capability number to the corresponding capability entry
> to finish the operation quickly.
>
> So we need a quicker way to access the entry for a given capability.
> We have two choices :
>
> 1) Unify both the tables to a static/dynamic sorted entry based on
> the capability number. This has the following drawbacks :
> a) The entries must be unique. i.e, no duplicate entries for a
> capability.
> b) Looses the separation of "features" vs. "errata" classification
> c) Statically sorting the list is error prone. Runtime sorting the
> array means more time for booting.
>
> 2) Keep an array of pointers to the capability sorted at boot time
> based on the capability.
> a) As for (1), the entries must be unique for a capability.
>
> This series implements (2) and uses the new list for optimizing the
> operations on the entries. As a prepatory step, we remove the
> duplicate entries for the same capabilities (Patch 1-3).
>

Thanks a lot for getting it sorted out! In case it'd help:

Reviewed-by: Vladimir Murzin <vladimir.murzin@arm.com>
Tested-by: Vladimir Murzin <vladimir.murzin@arm.com>

Cheers
Vladimir

>
> Suzuki K Poulose (7):
> arm64: capabilities: Merge entries for ARM64_WORKAROUND_CLEAN_CACHE
> arm64: capabilities: Merge duplicate Cavium erratum entries
> arm64: capabilities: Merge duplicate entries for Qualcomm erratum 1003
> arm64: capabilities: Speed up capability lookup
> arm64: capabilities: Optimize this_cpu_has_cap
> arm64: capabilities: Use linear array for detection and verification
> arm64: capabilities: Batch cpu_enable callbacks
>
> arch/arm64/include/asm/cpufeature.h | 3 +
> arch/arm64/include/asm/cputype.h | 2 +
> arch/arm64/kernel/cpu_errata.c | 94 ++++++++++----------
> arch/arm64/kernel/cpufeature.c | 165 ++++++++++++++++++++----------------
> 4 files changed, 145 insertions(+), 119 deletions(-)
>