Re: [PATCH] arm64: armv8_deprecated: Fix warning in isndep cpuhp starting process

From: "liwei (GF)" <liwei391@huawei.com>
To: Will Deacon <will@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>,
	Joel Granados <j.granados@samsung.com>,
	Luis Chamberlain <mcgrof@kernel.org>, <xiexiuqi@huawei.com>,
	<linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH] arm64: armv8_deprecated: Fix warning in isndep cpuhp starting process
Date: Tue, 21 May 2024 11:10:43 +0800	[thread overview]
Message-ID: <f1c64afa-91bf-4b2a-aa19-4918b3592ca4@huawei.com> (raw)
In-Reply-To: <20240430150638.GB14187@willie-the-truck>

On 2024/4/30 23:06, Will Deacon wrote:
> On Tue, Apr 23, 2024 at 05:35:01PM +0800, Wei Li wrote:
>> The function run_all_insn_set_hw_mode() is registered as startup callback
>> of 'CPUHP_AP_ARM64_ISNDEP_STARTING', it invokes set_hw_mode() methods of
>> all emulated instructions.
>>
>> As the STARTING callbacks are not expected to fail, if one of the
>> set_hw_mode() fails, e.g. due to el0 mixed-endian is not supported for
>> 'setend', it will report a warning:
>>
>> ```
>> CPU[2] cannot support the emulation of setend
>> CPU 2 UP state arm64/isndep:starting (136) failed (-22)
>> CPU2: Booted secondary processor 0x0000000002 [0x414fd0c1]
>> ```
>>
>> To fix it, add a check for INSN_UNAVAILABLE status and skip the process.
>>
>> Signed-off-by: Wei Li <liwei391@huawei.com>
>> ---
>>  arch/arm64/kernel/armv8_deprecated.c | 3 +++
>>  1 file changed, 3 insertions(+)
>>
>> diff --git a/arch/arm64/kernel/armv8_deprecated.c b/arch/arm64/kernel/armv8_deprecated.c
>> index dd6ce86d4332..b776e7424fe9 100644
>> --- a/arch/arm64/kernel/armv8_deprecated.c
>> +++ b/arch/arm64/kernel/armv8_deprecated.c
>> @@ -462,6 +462,9 @@ static int run_all_insn_set_hw_mode(unsigned int cpu)
>>  	for (int i = 0; i < ARRAY_SIZE(insn_emulations); i++) {
>>  		struct insn_emulation *insn = insn_emulations[i];
>>  		bool enable = READ_ONCE(insn->current_mode) == INSN_HW;
>> +		if (insn->status == INSN_UNAVAILABLE)
>> +			continue;
>> +
>>  		if (insn->set_hw_mode && insn->set_hw_mode(enable)) {
>>  			pr_warn("CPU[%u] cannot support the emulation of %s",
>>  				cpu, insn->name);
> 
> Isn't this part of the warning useful, though? ^^^
> 

Sorry I missed your replay, I think the warning here is unexpected.

As far as setend is concerned, the 'INSN_UNAVAILABLE' state is marked in armv8_deprecated_init(),
with a prompt message, and skipped in following register process too. So the warning here should
be intended to indicate the situation where set_hw_mode() should succeed.

Thanks,
Wei

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