From: Keqian Zhu <zhukeqian1@huawei.com>
To: Robin Murphy <robin.murphy@arm.com>, Will Deacon <will@kernel.org>
Cc: Jean-Philippe Brucker <jean-philippe@linaro.org>,
linux-kernel <linux-kernel@vger.kernel.org>,
iommu <iommu@lists.linux-foundation.org>,
Yang Yingliang <yangyingliang@huawei.com>,
linux-arm-kernel <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH 1/1] iommu/arm-smmu-v3: add support for BBML
Date: Fri, 29 Jan 2021 14:12:46 +0800 [thread overview]
Message-ID: <29fd5c20-faeb-1fd3-6535-4fca60463d01@huawei.com> (raw)
In-Reply-To: <301590f1-817b-d8eb-1585-31208cba18af@arm.com>
On 2021/1/29 0:17, Robin Murphy wrote:
> On 2021-01-28 15:18, Keqian Zhu wrote:
>>
>>
>> On 2021/1/27 17:39, Robin Murphy wrote:
>>> On 2021-01-27 07:36, Keqian Zhu wrote:
>>>>
>>>>
>>>> On 2021/1/27 10:01, Leizhen (ThunderTown) wrote:
>>>>>
>>>>>
>>>>> On 2021/1/26 18:12, Will Deacon wrote:
>>>>>> On Mon, Jan 25, 2021 at 08:23:40PM +0000, Robin Murphy wrote:
>>>>>>> Now we probably will need some degreee of BBML feature awareness for the
>>>>>>> sake of SVA if and when we start using it for CPU pagetables, but I still
>>>>>>> cannot see any need to consider it in io-pgtable.
>>>>>>
>>>>>> Agreed; I don't think this is something that io-pgtable should have to care
>>>>>> about.
>>>> Hi,
>>>>
>>>> I have a question here :-).
>>>> If the old table is not live, then the break procedure seems unnecessary. Do I miss something?
>>>
>>> The MMU is allowed to prefetch translations at any time, so not following the proper update procedure could still potentially lead to a TLB conflict, even if there's no device traffic to worry about disrupting.
>>>
>>> Robin.
>>
>> Thanks. Does the MMU you mention here includes MMU and SMMU? I know that at SMMU side, ATS can prefetch translation.
>
> Yes, both - VMSAv8 allows speculative translation table walks, so SMMUv3 inherits from there (per 3.21.1 "Translation tables and TLB invalidation completion behavior").
OK, I Get it. Thanks.
Keqian.
>
> Robin.
>
>>
>> Keqian
>>>
>>>> Thanks,
>>>> Keqian
>>>>
>>>>>
>>>>> Yes, the SVA works in stall mode, and the failed device access requests are not
>>>>> discarded.
>>>>>
>>>>> Let me look for examples. The BBML usage scenario was told by a former colleague.
>>>>>
>>>>>>
>>>>>> Will
>>>>>>
>>>>>> .
>>>>>>
>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> linux-arm-kernel mailing list
>>>>> linux-arm-kernel@lists.infradead.org
>>>>> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
>>>>> .
>>>>>
>>>> _______________________________________________
>>>> iommu mailing list
>>>> iommu@lists.linux-foundation.org
>>>> https://lists.linuxfoundation.org/mailman/listinfo/iommu
>>>>
>>> .
>>>
> .
>
prev parent reply other threads:[~2021-01-29 6:14 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-26 3:42 [PATCH 1/1] iommu/arm-smmu-v3: add support for BBML Zhen Lei
2021-01-22 12:51 ` Will Deacon
2021-01-22 13:00 ` Robin Murphy
2021-01-22 13:21 ` Leizhen (ThunderTown)
2021-01-22 13:26 ` Will Deacon
2021-01-23 10:20 ` Leizhen (ThunderTown)
2021-01-25 19:54 ` Robin Murphy
2021-01-23 10:08 ` Leizhen (ThunderTown)
2021-01-25 20:23 ` Robin Murphy
2021-01-26 10:12 ` Will Deacon
2021-01-27 2:01 ` Leizhen (ThunderTown)
2021-01-27 7:36 ` Keqian Zhu
2021-01-27 9:39 ` Robin Murphy
2021-01-28 15:18 ` Keqian Zhu
2021-01-28 16:17 ` Robin Murphy
2021-01-29 6:12 ` Keqian Zhu [this message]
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