linux-kernel - Re: [PATCH v4 01/17] iommu: Add hwpt_type with user_data for domain_alloc

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Message-ID: <ZS1+VMEo+0bCecui@Asurada-Nvidia>
Date:   Mon, 16 Oct 2023 11:17:56 -0700
From:   Nicolin Chen <nicolinc@...dia.com>
To:     Jason Gunthorpe <jgg@...dia.com>
CC:     Yi Liu <yi.l.liu@...el.com>, <joro@...tes.org>,
        <alex.williamson@...hat.com>, <kevin.tian@...el.com>,
        <robin.murphy@....com>, <baolu.lu@...ux.intel.com>,
        <cohuck@...hat.com>, <eric.auger@...hat.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>,
        <zhenzhong.duan@...el.com>, <joao.m.martins@...cle.com>
Subject: Re: [PATCH v4 01/17] iommu: Add hwpt_type with user_data for
 domain_alloc_user op

On Mon, Oct 16, 2023 at 08:54:07AM -0300, Jason Gunthorpe wrote:
> On Mon, Oct 16, 2023 at 11:28:15AM +0800, Yi Liu wrote:
> > On 2023/10/14 01:56, Nicolin Chen wrote:
> > > On Fri, Oct 13, 2023 at 11:04:56AM -0300, Jason Gunthorpe wrote:
> > > > On Fri, Oct 13, 2023 at 12:33:13PM +0800, Yi Liu wrote:
> > > > 
> > > > > not really. Below the users of the struct iommu_user_data in my current
> > > > > iommufd_nesting branch. Only the domain_alloc_user op has type as there
> > > > > can be multiple vendor specific alloc data types. Basically, I'm ok to
> > > > > make the change you suggested, just not sure if it is good to add type
> > > > > as it is only needed by one path.
> > > > 
> > > > I don't think we should ever have an opaque data blob without a type
> > > > tag..
> > > 
> > > I can add those "missing" data types, and then a driver will be
> > > responsible for sanitizing the type along with the data_len.
> > > 
> > > I notice that the enum iommu_hwpt_data_type in the posted patch
> > > is confined to the alloc_user uAPI. Perhaps we should share it
> > > with invalidate too:
> > 
> > invalidation path does not need a type field today as the data
> > type is vendor specific, vendor driver should know the data type
> > when calls in.
> 
> I'm not keen on that, what if a driver needs another type in the
> future?  You'd want to make the invalidation data format part of the
> domain allocation?

The invalidation data has hwpt_id so it's tied to a hwpt and its 
hwpt->domain. Would it be reasonable to have a different type of
invalidation data for the same type of hwpt?

With this being asked, I added it for our next version. At this
moment, it only does a sanity job:

// API
__iommu_copy_struct_from_user(void *dst_data,
			      const struct iommu_user_data *src_data,
			      unsigned int data_type, size_t data_len,
			      size_t min_len)
{
	if (src_data->type != data_type)
		return -EINVAL;

// Caller
	rc = iommu_copy_struct_from_user(&user_cfg, user_data,
					 IOMMU_HWPT_DATA_SELFTEST, iotlb);
	if (rc)
		return ERR_PTR(rc);

Thanks
Nic