linux-kernel - Re: [RFC PATCH v1 0/3] arm64: tlb: add support for TTL field

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Message-ID: <6279257b-2b8c-10d0-8bb8-b0f4b851febb@huawei.com>
Date:   Wed, 11 Mar 2020 19:29:35 +0800
From:   "yezhenyu (A)" <yezhenyu2@...wei.com>
To:     Marc Zyngier <maz@...nel.org>
CC:     <mark.rutland@....com>, <catalin.marinas@....com>,
        <will@...nel.org>, <aneesh.kumar@...ux.ibm.com>,
        <steven.price@....com>, <broonie@...nel.org>,
        <guohanjun@...wei.com>, <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <linux-arch@...r.kernel.org>,
        <linux-mm@...ck.org>, <arm@...nel.org>, <xiexiangyou@...wei.com>,
        <prime.zeng@...ilicon.com>, <zhangshaokun@...ilicon.com>
Subject: Re: [RFC PATCH v1 0/3] arm64: tlb: add support for TTL field

Hi Marc,

On 2020/3/11 17:12, Marc Zyngier wrote:
> Zhenyu,
> 
> On 2020-03-11 02:53, Zhenyu Ye wrote:
>> ARMv8.4-TTL provides the TTL field in tlbi instruction to indicate
>> the level of translation table walk holding the leaf entry for the
>> address that is being invalidated. Hardware can use this information
>> to determine if there was a risk of splintering.
>>
>> This set of patches adds TTL field to __TLBI_ADDR, and uses
>> Architecture-specific MM context to pass the TTL value to tlb interface.
>>
>> The default value of TTL is 0, which will not have any impact on the
>> TLB maintenance instructions. The last patch trys to use TTL field in
>> some obviously tlb-flush interface.
> 
> I have already posted some support for ARMv8.4-TTL as part of my NV series [1],
> patches 62, 67, 68 and 69. This only deals with Stage-2 translation so far.
> If you intend to add Stage-1, please build on top of what I have already posted
> (I can extract the patches on a separate branch if you want).
> 
> Thanks,
> 
>         M.
> 
> [1] https://lore.kernel.org/linux-arm-kernel/20200211174938.27809-1-maz@kernel.org/

I just readed your code changes to TTL. You pass the TTL value by changing the
function interface, which only involves the ARM and ARM64 architectures in Stage-2
translation.

However, in Stage-1, many common interfaces(such as flush_tlb_range) need to be
modified, which involves very much architectures. So I try to use MM context in
mm_struct to pass the TTL value.

I will send patch v2 based on top of your kvm-arm64/nv-5.6-rc1 branch soon.

https://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git/log/?h=kvm-arm64/nv-5.6-rc1


Thanks,
Zhenyu