linux-kernel - Re: [PATCH v3 0/6] iommu: Extend changing default domain to normal group

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Message-ID: <ZAqImOaQLMuWXhsv@nvidia.com>
Date:   Thu, 9 Mar 2023 21:32:08 -0400
From:   Jason Gunthorpe <jgg@...dia.com>
To:     Lu Baolu <baolu.lu@...ux.intel.com>, Joerg Roedel <joro@...tes.org>
Cc:     iommu@...ts.linux.dev, Christoph Hellwig <hch@...radead.org>,
        Kevin Tian <kevin.tian@...el.com>,
        Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 0/6] iommu: Extend changing default domain to normal
 group

On Mon, Mar 06, 2023 at 10:57:58AM +0800, Lu Baolu wrote:
> The IOMMU group sysfs interface allows users to change the default
> domain of a group. The current implementation uses device_lock() to make
> sure that the devices in the group are not bound to any driver and won't
> be bound during the process of changing the default domain. In order to
> avoid a possible deadlock caused by lock order of device_lock and
> group->mutex, it limits the functionality to singleton groups only.
> 
> The recently implemented DMA ownership framework can be applied here to
> replace device_lock(). In addition, use group->mutex to ensure that the
> iommu ops of the device are always valid during the process of changing
> default domain.
> 
> With above replacement and enhancement, the device_lock() could be
> removed and the singleton-group-only limitation could be removed.
> 
> This series is based on v6.3-rc1 with below series from Robin applied,
> https://lore.kernel.org/linux-iommu/cover.1674753627.git.robin.murphy@arm.com/

Joerg can you help Lu with patch planning here? Can we get Robin's
series, this one and a maybe few more that clash on this for the
cycle?

Should this one go before Robin's series? It didn't seem obviously
dependent beyond using the same helper function?

Thanks,
Jason