linux-kernel - Re: [PATCH 1/6] iommu: Add new iommu op to get iommu hardware information

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Date:   Mon, 13 Feb 2023 16:46:44 +0800
From:   Baolu Lu <baolu.lu@...ux.intel.com>
To:     Binbin Wu <binbin.wu@...ux.intel.com>, Yi Liu <yi.l.liu@...el.com>,
        joro@...tes.org, alex.williamson@...hat.com, jgg@...dia.com,
        kevin.tian@...el.com, robin.murphy@....com
Cc:     baolu.lu@...ux.intel.com, cohuck@...hat.com, eric.auger@...hat.com,
        nicolinc@...dia.com, kvm@...r.kernel.org, mjrosato@...ux.ibm.com,
        chao.p.peng@...ux.intel.com, yi.y.sun@...ux.intel.com,
        peterx@...hat.com, jasowang@...hat.com,
        shameerali.kolothum.thodi@...wei.com, lulu@...hat.com,
        suravee.suthikulpanit@....com, iommu@...ts.linux.dev,
        linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH 1/6] iommu: Add new iommu op to get iommu hardware
 information

On 2023/2/13 10:36, Binbin Wu wrote:
> 
> On 2/9/2023 12:16 PM, Yi Liu wrote:
>> From: Lu Baolu <baolu.lu@...ux.intel.com>
>>
>> Introduce a new iommu op get
> 
> get -> to get
> 
> 
>> the IOMMU hardware capabilities for iommufd.
>> This information will be used by any vIOMMU driver which is owned by
>> userspace.
>>
>> This op chooses to make the special parameters opaque to the core. This
>> suits the current usage model where accessing any of the IOMMU device
>> special parameters does require a userspace driver that matches the 
>> kernel
>> driver. If a need for common parameters, implemented similarly by several
>> drivers, arises then there is room in the design to grow a generic 
>> parameter
>> set as well. No warpper
> 
> warpper -> wrapper

Thanks, will update.

> 
>>   API is added as it is supposed to be used by
>> iommufd only.
>>
>> Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
>> Signed-off-by: Yi Liu <yi.l.liu@...el.com>
>> Signed-off-by: Nicolin Chen <nicolinc@...dia.com>
>> ---
>>   include/linux/iommu.h        | 8 ++++++++
>>   include/uapi/linux/iommufd.h | 6 ++++++
>>   2 files changed, 14 insertions(+)
>>
>> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
>> index cb586d054c57..97b398d19fd2 100644
>> --- a/include/linux/iommu.h
>> +++ b/include/linux/iommu.h
>> @@ -15,6 +15,7 @@
>>   #include <linux/of.h>
>>   #include <linux/ioasid.h>
>>   #include <uapi/linux/iommu.h>
>> +#include <uapi/linux/iommufd.h>
>>   #define IOMMU_READ    (1 << 0)
>>   #define IOMMU_WRITE    (1 << 1)
>> @@ -223,6 +224,11 @@ struct iommu_iotlb_gather {
>>   /**
>>    * struct iommu_ops - iommu ops and capabilities
>>    * @capable: check capability
>> + * @hw_info: IOMMU hardware capabilities. The type of the returned 
>> data is
>> + *           defined in include/uapi/linux/iommufd.h. The data buffer is
>> + *           allocated in the IOMMU driver and the caller should free it
>> + *           after use. Return the data buffer if success, or ERR_PTR on
>> + *          failure.
>>    * @domain_alloc: allocate iommu domain
>>    * @probe_device: Add device to iommu driver handling
>>    * @release_device: Remove device from iommu driver handling
>> @@ -252,6 +258,7 @@ struct iommu_iotlb_gather {
>>    */
>>   struct iommu_ops {
>>       bool (*capable)(struct device *dev, enum iommu_cap);
>> +    void *(*hw_info)(struct device *dev, u32 *length);
>>       /* Domain allocation and freeing by the iommu driver */
>>       struct iommu_domain *(*domain_alloc)(unsigned iommu_domain_type);
>> @@ -280,6 +287,7 @@ struct iommu_ops {
>>       void (*remove_dev_pasid)(struct device *dev, ioasid_t pasid);
>>       const struct iommu_domain_ops *default_domain_ops;
>> +    enum iommu_device_data_type driver_type;
> 
> 
> How to understand the name "iommu_device_data_type"?

This is to tell userspace which type of IOMMU the returned information
comes from, Intel VT-d, ARM or others...

> Is it just refer to the driver types or it has a more generic meaning?

IOMMU driver sets this field to distinguish different IOMMU hardware.

Best regards,
baolu