linux-kernel - Re: [PATCH v4 10/17] iommufd: Support IOMMU_HWPT

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Message-ID: <ZSmvkxuEq7M13KYE@Asurada-Nvidia>
Date:   Fri, 13 Oct 2023 13:58:59 -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 10/17] iommufd: Support IOMMU_HWPT_ALLOC allocation
 with user data

On Fri, Oct 13, 2023 at 12:19:23PM -0300, Jason Gunthorpe wrote:
> On Thu, Sep 21, 2023 at 12:51:31AM -0700, Yi Liu wrote:
> > IOMMU_HWPT_ALLOC already supports iommu_domain allocation for usersapce.
> > But it can only allocate a hw_pagetable that associates to a given IOAS,
> > i.e. only a kernel-managed hw_pagetable of IOMMU_HWPT_TYPE_DEFAULT type.
> > 
> > IOMMU drivers can now support user-managed hw_pagetables, for two-stage
> > translation use cases, that require user data input from the user space.
> > 
> > Extend the IOMMU_HWPT_ALLOC ioctl to accept non-default hwpt_type with a
> > type specified user data. Also, update the @pt_id to accept hwpt_id too
> > besides an ioas_id. Then, pass them to the downstream alloc_fn().
> > 
> > Co-developed-by: Nicolin Chen <nicolinc@...dia.com>
> > Signed-off-by: Nicolin Chen <nicolinc@...dia.com>
> > Signed-off-by: Yi Liu <yi.l.liu@...el.com>
> > ---
> >  drivers/iommu/iommufd/hw_pagetable.c | 19 ++++++++++++++++++-
> >  include/uapi/linux/iommufd.h         | 23 +++++++++++++++++++++--
> >  2 files changed, 39 insertions(+), 3 deletions(-)
> 
> Can we also come with a small vt-d patch that does implement an op for
> this? Or is it too big?
> 
> It would be nice if we could wrap IOMMU_HWPT_ALLOC into one
> self-contained series and another series for invalidate.

We now only use IOMMU_HWPT_ALLOC for nested domain allocations,
which won't be supported until the cache_invalidate_user ops is
preset?

/* e.g. the following piece is in iommufd_user_managed_hwpt_alloc */

+       /* Driver is buggy by missing cache_invalidate_user in domain_ops */
+       if (WARN_ON_ONCE(!hwpt->domain->ops->cache_invalidate_user)) {
+               rc = -EINVAL;
+               goto out_abort;
+       }

Thanks
Nic