From: Anshuman Khandual <anshuman.khandual@arm.com>
To: Will Deacon <will@kernel.org>, Catalin Marinas <catalin.marinas@arm.com>
Cc: mark.rutland@arm.com, Mark Brown <broonie@kernel.org>,
linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
Suzuki K Poulose <suzuki.poulose@arm.com>
Subject: Re: [PATCH V2] arm64/cpufeature: Add get_arm64_ftr_reg_nowarn()
Date: Wed, 27 May 2020 07:56:30 +0530 [thread overview]
Message-ID: <ca38b2c0-533f-9b98-46a2-37ba8bf21d83@arm.com> (raw)
In-Reply-To: <20200526194648.GA2206@willie-the-truck>
On 05/27/2020 01:16 AM, Will Deacon wrote:
> On Tue, May 26, 2020 at 04:01:35PM +0100, Catalin Marinas wrote:
>> On Tue, May 26, 2020 at 07:09:13PM +0530, Anshuman Khandual wrote:
>>> @@ -632,8 +654,6 @@ static void __init init_cpu_ftr_reg(u32 sys_reg, u64 new)
>>> const struct arm64_ftr_bits *ftrp;
>>> struct arm64_ftr_reg *reg = get_arm64_ftr_reg(sys_reg);
>>>
>>> - BUG_ON(!reg);
>>> -
>>> for (ftrp = reg->ftr_bits; ftrp->width; ftrp++) {
>>> u64 ftr_mask = arm64_ftr_mask(ftrp);
>>> s64 ftr_new = arm64_ftr_value(ftrp, new);
>>> @@ -762,7 +782,6 @@ static int check_update_ftr_reg(u32 sys_id, int cpu, u64 val, u64 boot)
>>> {
>>> struct arm64_ftr_reg *regp = get_arm64_ftr_reg(sys_id);
>>>
>>> - BUG_ON(!regp);
>>> update_cpu_ftr_reg(regp, val);
>>> if ((boot & regp->strict_mask) == (val & regp->strict_mask))
>>> return 0;
>>> @@ -776,9 +795,6 @@ static void relax_cpu_ftr_reg(u32 sys_id, int field)
>>> const struct arm64_ftr_bits *ftrp;
>>> struct arm64_ftr_reg *regp = get_arm64_ftr_reg(sys_id);
>>>
>>> - if (WARN_ON(!regp))
>>> - return;
>>
>> I think Will wanted an early return in all these functions not just
>> removing the BUG_ON(). I'll let him clarify.
>
> Yes, the callers need to check the pointer and return early.
Sure, will do. But for check_update_ftr_reg(), a feature register search
failure should be treated as a success (0) or a failure (1). What should
it return ? Seems bit tricky, as there are good reasons to go either way.
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next prev parent reply other threads:[~2020-05-27 2:27 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-26 13:39 [PATCH V2] arm64/cpufeature: Add get_arm64_ftr_reg_nowarn() Anshuman Khandual
2020-05-26 14:04 ` Suzuki K Poulose
2020-05-26 14:03 ` Anshuman Khandual
2020-05-26 15:01 ` Catalin Marinas
2020-05-26 19:46 ` Will Deacon
2020-05-27 2:26 ` Anshuman Khandual [this message]
2020-05-27 7:53 ` Will Deacon
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