linux-kernel - Re: [PATCH RFC v2 0/3] Add set_dev_data and unset_dev

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Date:   Fri, 21 Apr 2023 11:19:20 -0700
From:   Nicolin Chen <nicolinc@...dia.com>
To:     Jason Gunthorpe <jgg@...dia.com>
CC:     "Tian, Kevin" <kevin.tian@...el.com>,
        "alex.williamson@...hat.com" <alex.williamson@...hat.com>,
        "robin.murphy@....com" <robin.murphy@....com>,
        "eric.auger@...hat.com" <eric.auger@...hat.com>,
        "Liu, Yi L" <yi.l.liu@...el.com>,
        "baolu.lu@...ux.intel.com" <baolu.lu@...ux.intel.com>,
        "will@...nel.org" <will@...nel.org>,
        "joro@...tes.org" <joro@...tes.org>,
        "shameerali.kolothum.thodi@...wei.com" 
        <shameerali.kolothum.thodi@...wei.com>,
        "jean-philippe@...aro.org" <jean-philippe@...aro.org>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "iommu@...ts.linux.dev" <iommu@...ts.linux.dev>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH RFC v2 0/3] Add set_dev_data and unset_dev_data support

On Fri, Apr 21, 2023 at 02:59:37PM -0300, Jason Gunthorpe wrote:
> On Fri, Apr 21, 2023 at 10:37:22AM -0700, Nicolin Chen wrote:
> 
> > How about the following piece? Needs a test with QEMU though..
> > 
> > static const size_t iommufd_device_data_size[] = {
> > 	[IOMMU_HW_INFO_TYPE_NONE] = 0,
> > 	[IOMMU_HW_INFO_TYPE_INTEL_VTD] = 0,
> > 	[IOMMU_HW_INFO_TYPE_ARM_SMMUV3] =
> > 		sizeof(struct iommu_device_data_arm_smmuv3),
> > };
> 
> If we need more than one of these things we'll need a better
> solution..

How about adding ops->device_data_size to store the value?

And, since we have a few size arrays in hw_pagetable.c too,
perhaps a new structure in ops packing all these sizes can
clean up a bit things too? For example,

static struct iommu_user_data_size arm_smmu_user_data_size = {
	.device_data_size = sizeof(iommu_device_data_arm_smmuv3),
	.hwpt_alloc_data_size = sizeof(iommu_hwpt_alloc_arm_smmuv3),
	.hwpt_invalidate_data_size = sizeof(iommu_hwpt_invalidate_arm_smmuv3),
}

The hwpt_xxx_data_size might be in form of arrays for multi-
HWPT_TYPE support.

> > 	rc = ops->set_dev_data_user(idev->dev, data);
> 
> Where will the iommu driver store the vsid to sid xarray from these
> arguments?

The ARM structure packs a vsid. For example:

static int arm_smmu_set_data(struct device *dev, const void *user_data)
{
	const struct iommufd_device_data_arm_smmuv3 *data = user_data;
	struct arm_smmu_master *master = dev_iommu_priv_get(dev);
	struct arm_smmu_stream *stream = &master->streams[0];
	struct arm_smmu_device *smmu = master->smmu;
	u32 sid_user = data->sid;
	int ret = 0;

	if (!sid_user)
		return -EINVAL;

	ret = xa_alloc(&smmu->streams_user, &sid_user, stream,
			XA_LIMIT(sid_user, sid_user), GFP_KERNEL_ACCOUNT);
	if (ret)
		return ret;
	stream->id_user = sid_user;
	return 0;
}

Thanks
Nic