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Re: [XEN][PATCH v10 12/20] xen/smmu: Add remove_device callback for smmu_iommu ops
- To: Stefano Stabellini <sstabellini@xxxxxxxxxx>
- From: Michal Orzel <michal.orzel@xxxxxxx>
- Date: Wed, 30 Aug 2023 11:17:30 +0200
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- Cc: Vikram Garhwal <vikram.garhwal@xxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxxx>, <julien@xxxxxxx>, Rahul Singh <rahul.singh@xxxxxxx>, Bertrand Marquis <bertrand.marquis@xxxxxxx>, Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>
- Delivery-date: Wed, 30 Aug 2023 09:17:50 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 30/08/2023 00:45, Stefano Stabellini wrote:
>
>
> On Tue, 29 Aug 2023, Michal Orzel wrote:
>> On 25/08/2023 10:02, Vikram Garhwal wrote:
>>> Add remove_device callback for removing the device entry from smmu-master
>>> using
>>> following steps:
>>> 1. Find if SMMU master exists for the device node.
>>> 2. Check if device is currently in use.
>> Since you removed a call to iommu_dt_device_is_assigned_locked(), you do not
>> check it from SMMU, right?
>> You are relying on a check done in iommu_remove_dt_device().
>> This wants to be mentioned. However, Julien suggested to do the check for
>> internal SMMU state.
>> Looking at the code, when the device is assigned, we do:
>> dev_iommu_domain(dev) = domain;
>> and when de-assigned:
>> dev_iommu_domain(dev) = NULL;
>>
>> This means that before calling remove_smmu_master() you could do:
>>
>> /* Make sure device is not assigned */
>> if (dev_iommu_domain(dev))
>> return -EBUSY;
>>
>> @Julien, @Stefano?
>
> I think it is OK without it, as we have a call to
> iommu_dt_device_is_assigned_locked(np) already in
> iommu_remove_dt_device?
Yes, but this would add an extra layer of protection by checking for IOMMU
domain for this device.
~Michal
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