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From: Lu Baolu <baolu.lu@linux.intel.com>
To: Will Deacon <will@kernel.org>, Ashok Raj <ashok.raj@intel.com>,
	robin.murphy@arm.com
Cc: iommu@lists.linux-foundation.org,
	Will Deacon <will.deacon@arm.com>, Christoph Hellwig <hch@lst.de>
Subject: Re: [Patch V8 0/3] iommu: Add support to change default domain of an iommu group
Date: Thu, 19 Nov 2020 10:36:15 +0800	[thread overview]
Message-ID: <fbfcf459-2014-ac40-70e6-0288160fb915@linux.intel.com> (raw)
In-Reply-To: <20201118135225.GC2177@willie-the-truck>

On 11/18/20 9:52 PM, Will Deacon wrote:
> 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...

Sure. I will send a v9 after Robin's review.

> 
> Will

Best regards,
baolu
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      reply	other threads:[~2020-11-19  2:43 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
2020-11-19  2:36   ` Lu Baolu [this message]

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