linux-kernel - Re: [PATCH v4 2/3] iommu/vt-d: Track device aux-attach with subdevice_domain

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Message-ID: <20210107134906.GA3043@willie-the-truck>
Date:   Thu, 7 Jan 2021 13:49:07 +0000
From:   Will Deacon <will@...nel.org>
To:     Liu Yi L <yi.l.liu@...el.com>
Cc:     baolu.lu@...ux.intel.com, joro@...tes.org, kevin.tian@...el.com,
        ashok.raj@...el.com, jun.j.tian@...el.com,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        yi.y.sun@...el.com, dan.carpenter@...cle.com,
        Xin Zeng <xin.zeng@...el.com>
Subject: Re: [PATCH v4 2/3] iommu/vt-d: Track device aux-attach with
 subdevice_domain_info

On Thu, Jan 07, 2021 at 12:03:56AM +0800, Liu Yi L wrote:
> In the existing code, loop all devices attached to a domain does not
> include sub-devices attached via iommu_aux_attach_device().
> 
> This was found by when I'm working on the below patch, There is no
> device in the domain->devices list, thus unable to get the cap and
> ecap of iommu unit. But this domain actually has subdevice which is
> attached via aux-manner. But it is tracked by domain. This patch is
> going to fix it.
> 
> https://lore.kernel.org/kvm/1599734733-6431-17-git-send-email-yi.l.liu@intel.com/
> 
> And this fix goes beyond the patch above, such sub-device tracking is
> necessary for other cases. For example, flushing device_iotlb for a
> domain which has sub-devices attached by auxiliary manner.

Sorry, but I'm having a really hard time understanding what this patch is
doing based on this commit message. Baolu -- do you think you could reword
it for me please? No need to resend the patch.

Thanks,

Will