From: Will Deacon <will@kernel.org>
To: Ashok Raj <ashok.raj@intel.com>, robin.murphy@arm.com
Cc: Will Deacon <will.deacon@arm.com>,
iommu@lists.linux-foundation.org, Christoph Hellwig <hch@lst.de>
Subject: Re: [Patch V8 0/3] iommu: Add support to change default domain of an iommu group
Date: Wed, 18 Nov 2020 13:52:26 +0000 [thread overview]
Message-ID: <20201118135225.GC2177@willie-the-truck> (raw)
In-Reply-To: <20200925190620.18732-1-ashok.raj@intel.com>
On Fri, Sep 25, 2020 at 12:06:17PM -0700, Ashok Raj wrote:
> Presently, the default domain of an iommu group is allocated during boot time
> and it cannot be changed later. So, the device would typically be either in
> identity (pass_through) mode or the device would be in DMA mode as long as the
> system is up and running. There is no way to change the default domain type
> dynamically i.e. after booting, a device cannot switch between identity mode and
> DMA mode.
>
> Assume a use case wherein the privileged user would want to use the device in
> pass-through mode when the device is used for host so that it would be high
> performing. Presently, this is not supported. Hence add support to change the
> default domain of an iommu group dynamically.
>
> Support this by writing to a sysfs file, namely
> "/sys/kernel/iommu_groups/<grp_id>/type".
>
> Testing:
> --------
> Tested by dynamically changing storage device (nvme) from
> 1. identity mode to DMA and making sure file transfer works
> 2. DMA mode to identity mode and making sure file transfer works
> Tested only for intel_iommu/vt-d. Would appreciate if someone could test on AMD
> and ARM based machines.
>
> Based on iommu maintainer's 'next' branch.
Modulo my minor comments, I think this looks good for 5.11 if you can
please send a version 9.
Robin -- please can you give it the once-over too? I think root can break
things quite badly with this interface, but root can do that in other ways
anyway...
Will
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next prev parent reply other threads:[~2020-11-18 13:52 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-25 19:06 [Patch V8 0/3] iommu: Add support to change default domain of an iommu group Ashok Raj
2020-09-25 19:06 ` [Patch V8 1/3] " Ashok Raj
2020-11-18 13:51 ` Will Deacon
2020-11-19 2:18 ` Lu Baolu
2020-11-19 8:53 ` Will Deacon
2020-11-20 2:11 ` Lu Baolu
2020-11-20 11:03 ` Will Deacon
2020-11-20 11:27 ` Shameerali Kolothum Thodi
2020-11-20 13:09 ` Lu Baolu
2020-09-25 19:06 ` [Patch V8 2/3] iommu: Take lock before reading iommu group default domain type Ashok Raj
2020-09-25 19:06 ` [Patch V8 3/3] iommu: Document usage of "/sys/kernel/iommu_groups/<grp_id>/type" file Ashok Raj
2020-11-18 13:51 ` Will Deacon
2020-11-19 2:32 ` Lu Baolu
2020-11-19 8:55 ` Will Deacon
2020-11-20 2:13 ` Lu Baolu
2020-10-01 12:58 ` [Patch V8 0/3] iommu: Add support to change default domain of an iommu group Joerg Roedel
2020-10-01 13:51 ` Raj, Ashok
2020-11-18 13:52 ` Will Deacon [this message]
2020-11-19 2:36 ` Lu Baolu
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