Re: [RFC PATCH v2] arm64: cpufeatures: add support for tlbi range instructions

From: Hanjun Guo <guohanjun@huawei.com>
To: Will Deacon <will@kernel.org>
Cc: mark.rutland@arm.com, Rob Herring <robh@kernel.org>,
	wanghuiqiang <wanghuiqiang@huawei.com>,
	Anna.Chen@arm.com, Zhenyu Ye <yezhenyu2@huawei.com>,
	catalin.marinas@arm.com, suzuki.poulose@arm.com,
	'Matteo Carlini' <Matteo.Carlini@arm.com>,
	xiexiangyou@huawei.com, Linuxarm <linuxarm@huawei.com>,
	Shaokun Zhang <zhangshaokun@hisilicon.com>,
	tangnianyao@huawei.com, Marc Zyngier <maz@kernel.org>,
	linux-arm-kernel@lists.infradead.org, qiuzhenfa@hisilicon.com
Subject: Re: [RFC PATCH v2] arm64: cpufeatures: add support for tlbi range instructions
Date: Sat, 11 Apr 2020 14:24:40 +0800	[thread overview]
Message-ID: <66e88366-770c-d3b7-2005-b6ba7045fea8@huawei.com> (raw)
In-Reply-To: <20200410115446.GA24814@willie-the-truck>

Hi Will,

On 2020/4/10 19:54, Will Deacon wrote:
> On Fri, Apr 10, 2020 at 09:43:49AM +0800, Hanjun Guo wrote:
>> On 2019/11/20 9:29, Hanjun Guo wrote:
>>>>
>>>> I also wonder if the ARMv8.4-TTL extension (which I have patches for in
>>>> the nested virt series) requires the same kind of treatment (after all,
>>>> it has an implicit range based on the base granule size and level).
>>>>
>>>> In any way, this requires careful specification, and I don't think
>>>> we can improvise this on the ML... ;-)
>>>
>>> Sure :), the good news is that ARM officially announced will be
>>> working with Huawei again.
>>>
>>> So if I understand your point correctly, we need steps to take:
>>>    - ARM spec needs to make TIBi by range crystal clear and being
>>>      written down in the spec;
>>>    - Firmware description of supporting TLBi by range in system level
>>>      for both FDT and ACPI;
>>>    - Then upstream the code.
>>
>> Do we have update here? I noticed that the TLBI by rang for SMMU is
>> merged for upstream from Rob, any plan or progress for the CPU side?
>>
>> Sorry to ping you on the mailling list, our upcoming new chip has
>> this feature and it's good to enable it, so it's a bit urgent for us.
> 
> Have you tried look at the latest version of the patches rather than
> "pinging" old history? We're also in the merge window at the moment, so
> please cut us some slack.

Sorry, I think I missed something, do you mean the patch set for TTL
from Zhenyu?

> 
> I also fail to see the urgency. This thing is a pure performance play, and a
> fairly niche one at that. I'm not especially comfortable ripping up our TLBI
> code without being able to test it.

As discussed before, if it needs the ACPI spec update, it will take
much longer time to get it enabled in mainline kernel, that's the
"urgency", not to ask for merging this patch for this merge window.

Thanks
Hanjun

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