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

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Date:   Thu, 12 Oct 2023 17:34:58 -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 Tue, Oct 10, 2023 at 01:58:44PM -0300, Jason Gunthorpe wrote:
> On Thu, Sep 21, 2023 at 12:51:22AM -0700, Yi Liu wrote:
> > diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> > index 660dc1931dc9..12e12e5563e6 100644
> > --- a/include/linux/iommu.h
> > +++ b/include/linux/iommu.h
> > @@ -14,6 +14,7 @@
> >  #include <linux/err.h>
> >  #include <linux/of.h>
> >  #include <uapi/linux/iommu.h>
> > +#include <uapi/linux/iommufd.h>
> 
> Oh we should definately avoid doing that!
>   
> Maybe this is a good moment to start a new header file exclusively for
> iommu drivers and core subsystem to include?
> 
>  include/linux/iommu-driver.h
> 
> ?
> 
> Put iommu_copy_user_data() and  struct iommu_user_data in there
> 
> Avoid this include in this file.

By looking closer, it seems that we included the uapi header for:
+	struct iommu_domain *(*domain_alloc_user)(struct device *dev, u32 flags,
+						  enum iommu_hwpt_data_type data_type,
+						  struct iommu_domain *parent,
+						  const struct iommu_user_data *user_data);

So we could drop the include, and instead add this next to structs:
+enum iommu_hwpt_data_type;

Then it's not that necessary to have a new header? We could mark a
section of "driver exclusively functions" in iommu.h, I think.

> >  #define IOMMU_READ	(1 << 0)
> >  #define IOMMU_WRITE	(1 << 1)
> > @@ -227,6 +228,41 @@ struct iommu_iotlb_gather {
> >  	bool			queued;
> >  };
> >  
> > +/**
> > + * struct iommu_user_data - iommu driver specific user space data info
> > + * @uptr: Pointer to the user buffer for copy_from_user()
> > + * @len: The length of the user buffer in bytes
> > + *
> > + * A user space data is an uAPI that is defined in include/uapi/linux/iommufd.h
> > + * Both @uptr and @len should be just copied from an iommufd core uAPI structure
> > + */
> > +struct iommu_user_data {
> > +	void __user *uptr;
> > +	size_t len;
> > +};
> 
> Put the "hwpt_type" in here and just call it type

Ah, then domain_alloc_user can omit the enum iommu_hwpt_data_type.

Thanks!
Nic