linux-kernel - Re: [RFC PATCH] iommu/vt-d: Fix IOMMU field not populated on device hot re-plug

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Date:   Tue, 3 Sep 2019 09:29:40 +0800
From:   Lu Baolu <baolu.lu@...ux.intel.com>
To:     Janusz Krzysztofik <janusz.krzysztofik@...ux.intel.com>
Cc:     baolu.lu@...ux.intel.com, David Woodhouse <dwmw2@...radead.org>,
        Joerg Roedel <joro@...tes.org>,
        iommu@...ts.linux-foundation.org, intel-gfx@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org,
        Michał Wajdeczko <michal.wajdeczko@...el.com>
Subject: Re: [RFC PATCH] iommu/vt-d: Fix IOMMU field not populated on device
 hot re-plug

Hi Janusz,

On 9/2/19 4:37 PM, Janusz Krzysztofik wrote:
>> I am not saying that keeping data is not acceptable. I just want to
>> check whether there are any other solutions.
> Then reverting 458b7c8e0dde and applying this patch still resolves the issue
> for me.  No errors appear when mappings are unmapped on device close after the
> device has been removed, and domain info preserved on device removal is
> successfully reused on device re-plug.

This patch doesn't look good to me although I agree that keeping data is
acceptable. It updates dev->archdata.iommu, but leaves the hardware
context/pasid table unchanged. This might cause problems somewhere.

> 
> Is there anything else I can do to help?

Can you please tell me how to reproduce the problem? Keeping the per
device domain info while device is unplugged is a bit dangerous because
info->dev might be a wild pointer. We need to work out a clean fix.

> 
> Thanks,
> Janusz
> 

Best regards,
Baolu