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

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Date:   Thu, 14 Dec 2023 10:26:10 +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 12/13/2023 7:59 PM, Baolu Lu wrote:
> On 2023/12/13 11:46, Ethan Zhao wrote:
>> For those endpoint devices connect to system via hotplug capable ports,
>> users could request a warm reset to the device by flapping device's link
>> through setting the slot's link control register, as pciehpt_ist() DLLSC
>> interrupt sequence response, pciehp will unload the device driver and
>> then power it off.
>
> Is it possible for pciehp to disable ATS on the device before unloading
> the driver? Or should the device follow some specific steps to warm
> reset the device?
>
In this case, link down first, then pciehp_ist() got DLLSC interrupt to 
know

that, I don't think it makes sense to disable device ATS here, but it could

flag the device is ATS disabled, well,  "disconnected" is enough to let

vt-d like software knows the device state.


> What happens if IOMMU issues device TLB invalidation after link down but
> before pci_dev_is_disconnected() returns true?

Seems it wouldn't happen with hotplug cases, safe_removal or

supprise_removal.



Thanks,

Ethan

>
> Best regards,
> baolu