linux-kernel - Re: [PATCH 0/2] iommufd: Only enforce_cache

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Date:   Mon, 23 Oct 2023 11:09:27 +0800
From:   Baolu Lu <baolu.lu@...ux.intel.com>
To:     "Tian, Kevin" <kevin.tian@...el.com>,
        Nicolin Chen <nicolinc@...dia.com>,
        "jgg@...dia.com" <jgg@...dia.com>
Cc:     baolu.lu@...ux.intel.com, "joro@...tes.org" <joro@...tes.org>,
        "will@...nel.org" <will@...nel.org>,
        "robin.murphy@....com" <robin.murphy@....com>,
        "iommu@...ts.linux.dev" <iommu@...ts.linux.dev>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Liu, Yi L" <yi.l.liu@...el.com>
Subject: Re: [PATCH 0/2] iommufd: Only enforce_cache_coherency when allocating
 hwpt

On 10/23/23 10:55 AM, Tian, Kevin wrote:
>> From: Baolu Lu <baolu.lu@...ux.intel.com>
>> Sent: Saturday, October 21, 2023 9:33 AM
>>
>> On 2023/10/21 8:37, Nicolin Chen wrote:
>>> https://lore.kernel.org/linux-
>> iommu/20231020135501.GG3952@...dia.com/
>>> The conversation above concluded that a hwpt should only enforce cache
>>> coherency per device at the stage of its allocation, and it should not
>>> be changed or updated in the attach/replace routines.
>>>
>>> Add two patches dropping the enforce_cache_coherency calls from attach
>>> and replce routines respectively, since they were introduced with two
>>> different commits.
>>>
>>> Nicolin Chen (2):
>>>     iommufd/device: Drop enforce_cache_coherency in
>>>       iommufd_device_do_replace
>>>     iommufd/device: Drop enforce_cache_coherency in
>>>       iommufd_hw_pagetable_attach
>>>
>>>    drivers/iommu/iommufd/device.c          | 19 ++-----------------
>>>    drivers/iommu/iommufd/hw_pagetable.c    |  2 +-
>>>    drivers/iommu/iommufd/iommufd_private.h |  1 -
>>>    3 files changed, 3 insertions(+), 19 deletions(-)
>>
>> Hi Kevin and Jason,
>>
>> With these two fixes, there's no issue in the intel driver any more. Do
>> I understand it right?
>>
> 
> But code-wise it's still good to explicitly disallow enforce-cc on a
> non-empty domain if there is no plan to support it. Just no Fix to
> stable.

Yes. Make sense. The device driver implementation should be self-
contained.

Best regards,
baolu