Re: [PATCH v8 01/13] x86/apic: Construct a selector for the interrupt delivery mode

From: Dou Liyang <douly.fnst@cn.fujitsu.com>
To: Baoquan He <bhe@redhat.com>
Cc: <x86@kernel.org>, <linux-kernel@vger.kernel.org>,
	<tglx@linutronix.de>, <mingo@kernel.org>, <hpa@zytor.com>,
	<rjw@rjwysocki.net>, <bp@alien8.de>, <indou.takao@jp.fujitsu.com>,
	<izumi.taku@jp.fujitsu.com>
Subject: Re: [PATCH v8 01/13] x86/apic: Construct a selector for the interrupt delivery mode
Date: Wed, 13 Sep 2017 11:48:03 +0800	[thread overview]
Message-ID: <33509937-ab65-c250-394e-3f17647271a2@cn.fujitsu.com> (raw)
In-Reply-To: <20170913023043.GG12824@x1>

Hi Baoquan,

At 09/13/2017 10:30 AM, Baoquan He wrote:
> Hi dou,
>
> On 09/12/17 at 09:20am, Dou Liyang wrote:
>> I thought again and again, I would not change this check logic.
>>
>> Because actually, we have three possibilities:
>>
>>   1. ACPI on chip
>>   2. 82489DX
>>   3. no APIC
>>
>> lapic_is_integrated() is used to check the APIC's type which is
>> APIC on chip or 82489DX. It has a prerequisite, we should avoid
>> the third possibility(no APIC) first, which is decided by
>> boot_cpu_has(X86_FEATURE_APIC) and smp_found_config. So, the original
>> logic:
>>
>> if (!boot_cpu_has(X86_FEATURE_APIC) && !smp_found_config)
>
> I won't insist that the logic need be changed. From the test result, the
> patchset works very well with notsc specified. And the whole patchset
> looks not risky. Maybe the patch putting acpi_early_init() earlier can
> be posted independently and involve other ARCHes maintainer to review.
>

Yes,  I will send it as an independent patch, and Cc other ARCH
maintainers

> About the code logic, I think the confusion comes from the unclear
> condition check. E.g the above case, you said it's used to check
> discrete apic, in fact !boot_cpu_has(X86_FEATURE_APIC) could means 3
> cases:
> 1) discrete apic
> 2) no apic
> 3) integrated apic but disabled by bios.

Indeed

>
> See, that's why it's confusing, the condition of judgement is not
> adequate. I don't know why the code contributer wanted to check discrete
> apic case with it.
>
> Anyway, after discussion, it's clear to me now. And the code works well.
> So it's up to you to change it or not. Except of this place, the whole
> patchset looks good.

Thank you very much for your review and test.

Thanks,
	dou.
>
> Thanks
> Baoquan
>
>>
>> ...is not just for 82489DX, but also for no APIC.
>>
>> It looks more correct and understandable than us.
>>
>> I am sorry my comments were wrong, and misled us. I will modify it
>> in my next version.
>>
>> BTW, How about your test result, is this series OK?
>>
>> Thanks,
>> 	dou.
>>
>>
>
>
>