linux-kernel - RE: [PATCH v2 2/4] iommu: Add new iommu op to get iommu hardware information

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Date:   Fri, 17 Mar 2023 00:08:25 +0000
From:   "Tian, Kevin" <kevin.tian@...el.com>
To:     Baolu Lu <baolu.lu@...ux.intel.com>,
        "Liu, Yi L" <yi.l.liu@...el.com>,
        "joro@...tes.org" <joro@...tes.org>,
        "alex.williamson@...hat.com" <alex.williamson@...hat.com>,
        "jgg@...dia.com" <jgg@...dia.com>,
        "robin.murphy@....com" <robin.murphy@....com>
CC:     "cohuck@...hat.com" <cohuck@...hat.com>,
        "eric.auger@...hat.com" <eric.auger@...hat.com>,
        "nicolinc@...dia.com" <nicolinc@...dia.com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "mjrosato@...ux.ibm.com" <mjrosato@...ux.ibm.com>,
        "chao.p.peng@...ux.intel.com" <chao.p.peng@...ux.intel.com>,
        "yi.y.sun@...ux.intel.com" <yi.y.sun@...ux.intel.com>,
        "peterx@...hat.com" <peterx@...hat.com>,
        "jasowang@...hat.com" <jasowang@...hat.com>,
        "shameerali.kolothum.thodi@...wei.com" 
        <shameerali.kolothum.thodi@...wei.com>,
        "lulu@...hat.com" <lulu@...hat.com>,
        "suravee.suthikulpanit@....com" <suravee.suthikulpanit@....com>,
        "iommu@...ts.linux.dev" <iommu@...ts.linux.dev>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-kselftest@...r.kernel.org" <linux-kselftest@...r.kernel.org>
Subject: RE: [PATCH v2 2/4] iommu: Add new iommu op to get iommu hardware
 information

> From: Baolu Lu <baolu.lu@...ux.intel.com>
> Sent: Thursday, March 16, 2023 4:30 PM
> 
> On 2023/3/16 16:16, Tian, Kevin wrote:
> >> + *           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
> >> @@ -246,11 +252,17 @@ struct iommu_iotlb_gather {
> >>    * @remove_dev_pasid: Remove any translation configurations of a
> specific
> >>    *                    pasid, so that any DMA transactions with this pasid
> >>    *                    will be blocked by the hardware.
> >> + * @driver_type: One of enum iommu_hw_info_type. This is used in the
> >> hw_info
> >> + *               reporting path. For the drivers that supports it, a unique
> >> + *               type should be defined. For the driver that does not support
> >> + *               it, this field is the IOMMU_HW_INFO_TYPE_DEFAULT that is 0.
> >> + *               Hence, such drivers do not need to care this field.
> > The meaning of "driver_type" is much broader than reporting hw_info.
> >
> > let's be accurate to call it as "hw_info_type". and while we have two
> > separate fields for one feature where is the check enforced on whether
> > both are provided?
> >
> > Is it simpler to return the type directly in @hw_info?
> 
> If I remember correctly, the vendor iommu type and hardware info are
> reported to user space separately.
> 

there is only one IOMMU_DEVICE_GET_HW_INFO cmd. It's written as:

	data = ops->hw_info(idev->dev, &data_len);
	copy_to_user(u64_to_user_ptr(cmd->data_ptr), data, length);
	cmd->out_data_type = ops->driver_type;