linux-kernel - Re: [PATCH 2/2] iommu/vt-d: don's issue devTLB flush request when device is disconnected

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Message-ID: <a121f7ee-6993-4784-a199-e747643d441a@linux.intel.com>
Date: Fri, 15 Dec 2023 09:51:10 +0800
From: Ethan Zhao <haifeng.zhao@...ux.intel.com>
To: Baolu Lu <baolu.lu@...ux.intel.com>, bhelgaas@...gle.com,
 dwmw2@...radead.org, will@...nel.org, robin.murphy@....com
Cc: linux-pci@...r.kernel.org, iommu@...ts.linux.dev,
 linux-kernel@...r.kernel.org, Haorong Ye <yehaorong@...edance.com>
Subject: Re: [PATCH 2/2] iommu/vt-d: don's issue devTLB flush request when
 device is disconnected


On 12/15/2023 9:34 AM, Baolu Lu wrote:
> On 2023/12/15 9:03, Ethan Zhao wrote:
>>
>> 2. supprise_removal
>>
>>   Users remove the devece directly or bring the device link down/turn 
>> off
>>
>>   device power first by setting pci config space, link-down/not-present/
>>
>>   power-off are all handled by pciehp the same way 
>> "supprise_removal", in
>>
>>   such case, pciehp_ist() will flag the device as "disconnected" 
>> first, then
>>
>>   unconfig the devcie, unload driver, iommu release device(issing 
>> devTLB flush)
>>
>>   delete device. so we checking the device state could work such cases.
>
> If so, then it is fine for the iommu driver. As Robin said, if the
> device needs more cleanup, the iommu core should register a right
> callback to the driver core and handle it before the device goes away.
>
> Disabling PCI features seems to be a reasonable device cleanup. This
> gives us another reason to move ATS enabling/disabling out from the

For supprise_removal, device was already removed, powered-off, iommu

device-release got notification  or cleanup callback is  invoked to disable

ATS to not-present device etc ,

I didn't get the meaning to do so, perhaps I misunderstand ?

Thanks,

Ethan

> iommu subsystem. Once this is done, the device driver will enable ATS
> during its probe and disable it during its release. There will be no
> such workaround in the iommu driver anymore.
>
> Best regards,
> baolu