From: Suzuki K Poulose <suzuki.poulose@arm.com>
To: andrew.murray@arm.com, dave.martin@arm.com
Cc: mark.rutland@arm.com, libc-alpha@sourceware.org,
Szabolcs.Nagy@arm.com, catalin.marinas@arm.com,
will.deacon@arm.com, pb@pbcl.net, linux-api@vger.kernel.org,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v3 3/7] arm64: HWCAP: encapsulate elf_hwcap
Date: Tue, 2 Apr 2019 16:32:57 +0100 [thread overview]
Message-ID: <8f47d948-e5cd-68ab-b340-d40d3b11a3f5@arm.com> (raw)
In-Reply-To: <20190402150654.GD53702@e119886-lin.cambridge.arm.com>
Hi,
On 02/04/2019 16:06, Andrew Murray wrote:
> On Tue, Apr 02, 2019 at 03:58:21PM +0100, Dave Martin wrote:
>> On Mon, Apr 01, 2019 at 11:45:11AM +0100, Andrew Murray wrote:
>>> The introduction of AT_HWCAP2 introduced accessors which ensure that
>>> hwcap features are set and tested appropriately.
>>>
>>> Let's now mandate access to elf_hwcap via these accessors by making
>>> elf_hwcap static within cpufeature.c.
>>
>> Looks reasonable except for a couple of minor nits below.
>>
>> I had wondered whether putting these accessors out of line would affect
>> any hot paths, but I can't see these used from anything that looks like
>> a hot path. So we're probably fine.
>>
>> cpus_have_const_cap() is preferred for places where this matters,
>> anyway.
Btw, thats for cpu_hwcaps, which is completely different from elf_hwcaps.
>>
>> [...]
>>
>>> diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
>>> index 986ceeacd19f..84ca52fa75e5 100644
>>> --- a/arch/arm64/kernel/cpufeature.c
>>> +++ b/arch/arm64/kernel/cpufeature.c
>>> @@ -35,8 +35,7 @@
>>> #include <asm/traps.h>
>>> #include <asm/virt.h>
>>>
>>> -unsigned long elf_hwcap __read_mostly;
>>> -EXPORT_SYMBOL_GPL(elf_hwcap);
>>> +static unsigned long elf_hwcap __read_mostly;
>>
>> Now that this doesn't correspond directly to ELF_HWCAP any more and we
>> hide it, can we rename it to avoid confusion?
>>
>> Maybe "kernel_hwcap"?
>
> Yes this seems reasonable.
nit:
As mentioned above we have "cpu_hwcaps" for the features only internally
by the kernel. Naming it "kernel_hwcap" kind of looses the hint that the
major purpose is for userspace consumption and could easily confuse with
the poorly named "cpu_hwcaps" which should have been called kernel_hwcaps.
How about "user_hwcaps" ? Or preferrably something closer to that.
Cheers
Suzuki
next prev parent reply other threads:[~2019-04-02 15:32 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-01 10:45 [PATCH v3 0/7] arm64: Initial support for CVADP Andrew Murray
2019-04-01 10:45 ` [PATCH v3 1/7] arm64: Handle trapped DC CVADP Andrew Murray
2019-04-01 10:45 ` [PATCH v3 2/7] arm64: HWCAP: add support for AT_HWCAP2 Andrew Murray
2019-04-02 14:58 ` Dave Martin
2019-04-03 8:32 ` Andrew Murray
2019-04-03 9:11 ` Dave Martin
2019-04-03 9:29 ` Andrew Murray
2019-04-03 9:35 ` Dave Martin
2019-04-01 10:45 ` [PATCH v3 3/7] arm64: HWCAP: encapsulate elf_hwcap Andrew Murray
2019-04-02 14:58 ` Dave Martin
2019-04-02 15:06 ` Andrew Murray
2019-04-02 15:32 ` Suzuki K Poulose [this message]
2019-04-02 15:55 ` Dave Martin
2019-04-03 8:53 ` Andrew Murray
2019-04-03 9:13 ` Dave Martin
2019-04-01 10:45 ` [PATCH v3 4/7] arm64: Expose DC CVADP to userspace Andrew Murray
2019-04-01 10:45 ` [PATCH v3 5/7] arm64: add CVADP support to the cache maintenance helper Andrew Murray
2019-04-01 10:45 ` [PATCH v3 6/7] arm64: Advertise ARM64_HAS_DCPODP cpu feature Andrew Murray
2019-04-02 14:59 ` Dave Martin
2019-04-03 9:23 ` Andrew Murray
2019-04-03 9:32 ` Dave Martin
2019-04-03 9:57 ` Andrew Murray
2019-04-01 10:45 ` [PATCH v3 7/7] arm64: docs: document AT_HWCAP2 and unused AT_HWCAP bits Andrew Murray
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