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From: Lu Baolu <baolu.lu@linux.intel.com>
To: Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com>,
	iommu@lists.linux-foundation.org
Cc: Ashok Raj <ashok.raj@intel.com>,
	Will Deacon <will.deacon@arm.com>,
	Robin Murphy <robin.murphy@arm.com>,
	Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH V4 3/3] iommu: Document usage of "/sys/kernel/iommu_groups/<grp_id>/type" file
Date: Mon, 8 Jun 2020 09:50:58 +0800	[thread overview]
Message-ID: <41050628-4dd2-c31b-e870-36a40c5d9c7b@linux.intel.com> (raw)
In-Reply-To: <24102f22824b26cf4fa6ec1c84d176110b21c574.1591290586.git.sai.praneeth.prakhya@intel.com>

On 6/5/20 9:32 AM, Sai Praneeth Prakhya wrote:
> The default domain type of an iommu group can be changed by writing to
> "/sys/kernel/iommu_groups/<grp_id>/type" file. Hence, document it's usage
> and more importantly spell out its limitations.
> 
> Cc: Christoph Hellwig <hch@lst.de>
> Cc: Joerg Roedel <joro@8bytes.org>
> Cc: Ashok Raj <ashok.raj@intel.com>
> Cc: Will Deacon <will.deacon@arm.com>
> Cc: Lu Baolu <baolu.lu@linux.intel.com>

Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>

Best regards,
baolu

> Cc: Sohil Mehta <sohil.mehta@intel.com>
> Cc: Robin Murphy <robin.murphy@arm.com>
> Cc: Jacob Pan <jacob.jun.pan@linux.intel.com>
> Signed-off-by: Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com>
> ---
>   .../ABI/testing/sysfs-kernel-iommu_groups     | 30 +++++++++++++++++++
>   1 file changed, 30 insertions(+)
> 
> diff --git a/Documentation/ABI/testing/sysfs-kernel-iommu_groups b/Documentation/ABI/testing/sysfs-kernel-iommu_groups
> index 017f5bc3920c..a498daffeb0c 100644
> --- a/Documentation/ABI/testing/sysfs-kernel-iommu_groups
> +++ b/Documentation/ABI/testing/sysfs-kernel-iommu_groups
> @@ -33,3 +33,33 @@ Description:    In case an RMRR is used only by graphics or USB devices
>   		it is now exposed as "direct-relaxable" instead of "direct".
>   		In device assignment use case, for instance, those RMRR
>   		are considered to be relaxable and safe.
> +
> +What:		/sys/kernel/iommu_groups/<grp_id>/type
> +Date:		June 2020
> +KernelVersion:	v5.8
> +Contact:	Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com>
> +Description:	Let the user know the type of default domain in use by iommu
> +		for this group. A privileged user could request kernel to change
> +		the group type by writing to this file. Presently, only three
> +		types are supported
> +		1. DMA: All the DMA transactions from the device in this group
> +			are translated by the iommu.
> +		2. identity: All the DMA transactions from the device in this
> +			     group are *not* translated by the iommu.
> +		3. auto: Change to the type the device was booted with. When the
> +			 user reads the file he would never see "auto". This is
> +			 just a write only value.
> +		Note:
> +		-----
> +		A group type could be modified only when
> +		1. The group has *only* one device
> +		2. The device in the group is not bound to any device driver.
> +		   So, the user must first unbind the appropriate driver and
> +		   then change the default domain type.
> +		Caution:
> +		--------
> +		Unbinding a device driver will take away the driver's control
> +		over the device and if done on devices that host root file
> +		system could lead to catastrophic effects (the user might
> +		need to reboot the machine to get it to normal state). So, it's
> +		expected that the user understands what he is doing.
> 
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  reply	other threads:[~2020-06-08  1:55 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-05  1:32 [PATCH V4 0/3] iommu: Add support to change default domain of an iommu group Sai Praneeth Prakhya
2020-06-05  1:32 ` [PATCH V4 1/3] " Sai Praneeth Prakhya
2020-06-08  1:49   ` Lu Baolu
2020-06-30  9:16   ` Joerg Roedel
2020-07-01  3:04     ` Prakhya, Sai Praneeth
2020-07-14 18:23       ` Prakhya, Sai Praneeth
2020-07-22 13:52         ` Joerg Roedel
2020-07-22 17:14           ` Prakhya, Sai Praneeth
2020-06-05  1:32 ` [PATCH V4 2/3] iommu: Take lock before reading iommu group default domain type Sai Praneeth Prakhya
2020-06-08  1:50   ` Lu Baolu
2020-06-05  1:32 ` [PATCH V4 3/3] iommu: Document usage of "/sys/kernel/iommu_groups/<grp_id>/type" file Sai Praneeth Prakhya
2020-06-08  1:50   ` Lu Baolu [this message]
2020-06-26 21:34 ` [PATCH V4 0/3] iommu: Add support to change default domain of an iommu group Prakhya, Sai Praneeth

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