Re: [PATCH 0/8] x86, acpi: Move acpi_initrd_override() earlier.

From: Zhang Yanfei <zhangyanfei.yes@gmail.com>
To: Toshi Kani <toshi.kani@hp.com>
Cc: Tejun Heo <tj@kernel.org>, Tang Chen <tangchen@cn.fujitsu.com>,
	konrad.wilk@oracle.com, robert.moore@intel.com,
	lv.zheng@intel.com, rjw@sisk.pl, lenb@kernel.org,
	tglx@linutronix.de, mingo@elte.hu, hpa@zytor.com,
	akpm@linux-foundation.org, trenn@suse.de, yinghai@kernel.org,
	jiang.liu@huawei.com, wency@cn.fujitsu.com, laijs@cn.fujitsu.com,
	isimatu.yasuaki@jp.fujitsu.com, izumi.taku@jp.fujitsu.com,
	mgorman@suse.de, minchan@kernel.org, mina86@mina86.com,
	gong.chen@linux.intel.com, vasilis.liaskovitis@profitbricks.com,
	lwoodman@redhat.com, riel@redhat.com, jweiner@redhat.com,
	prarit@redhat.com, zhangyanfei@cn.fujitsu.com,
	yanghy@cn.fujitsu.com, x86@kernel.org, linux-doc@vger.kernel.org,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	linux-acpi@vger.kernel.org
Subject: Re: [PATCH 0/8] x86, acpi: Move acpi_initrd_override() earlier.
Date: Sat, 24 Aug 2013 01:29:56 +0800	[thread overview]
Message-ID: <52179C14.20407@gmail.com> (raw)
In-Reply-To: <1377278016.10300.814.camel@misato.fc.hp.com>

Hi Toshi,

On 08/24/2013 01:13 AM, Toshi Kani wrote:
> Hello,
> 
> On Fri, 2013-08-23 at 12:24 -0400, Tejun Heo wrote:
>> On Fri, Aug 23, 2013 at 10:14:08AM -0600, Toshi Kani wrote:
>>> I still think acpi table info should be available earlier, but I do not
>>> think I can convince you on this.  This can be religious debate.
>>
>> I'm curious.  If there aren't substantial enough benefits, why would
>> you still want to pull it earlier when it brings in things like initrd
>> override and crafting the code carefully so that it's safe to execute
>> it from different address modes and so on?  Please note that x86 is
>> not ia64.  The early environment is completely different not only
>> technically but also in its diversity and suckiness.  It wasn't too
>> long ago that vendors were screwing up ACPI left and right.  It has
>> been getting better but there's a reason why, for example, we still
>> consider e820 to be the authoritative information over ACPI.
> 
> Firmware generates tables, and provides them via some interface.  Memory
> map table can be provided via e820 or EFI memory map.  Memory topology
> table is provided via ACPI.  I agree to prioritize one table over the
> other when there is overlap.  But in the end, it is the firmware that
> generates the tables.  Because it is provided via ACPI does not make it
> suddenly unreliable.  I think table info from e820/EFI/ACPI should be
> available at the same time.  To me, it makes more sense to use the
> hotplug info to initialize memblock than try to find a way to workaround
> without it.  

Yeah, agreed. But sigh.... on x86, we have ACPI initrd override, so we still
cannot convince Tj....

I think we will continue to be in that way to find a
> workaround in this direction. 
> 
> I came from ia64 background, and am not very familiar with x86.  So, you
> may be very right about that x86 is different.  I also agree that initrd
> is making it unnecessarily complicated.  We may see some initial issues,
> but my hope is that the code gets matured over the time.
> 
> Thanks,
> -Toshi
> 

-- 
Thanks.
Zhang Yanfei

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