linux-kernel - Re: [PATCH v3 09/17] iommufd: Add IOMMU_HWPT

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Date:   Wed, 2 Aug 2023 20:13:35 -0700
From:   Nicolin Chen <nicolinc@...dia.com>
To:     "Liu, Yi L" <yi.l.liu@...el.com>
CC:     Jason Gunthorpe <jgg@...dia.com>,
        "joro@...tes.org" <joro@...tes.org>,
        "alex.williamson@...hat.com" <alex.williamson@...hat.com>,
        "Tian, Kevin" <kevin.tian@...el.com>,
        "robin.murphy@....com" <robin.murphy@....com>,
        "baolu.lu@...ux.intel.com" <baolu.lu@...ux.intel.com>,
        "cohuck@...hat.com" <cohuck@...hat.com>,
        "eric.auger@...hat.com" <eric.auger@...hat.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>,
        "Duan, Zhenzhong" <zhenzhong.duan@...el.com>
Subject: Re: [PATCH v3 09/17] iommufd: Add IOMMU_HWPT_INVALIDATE

On Thu, Aug 03, 2023 at 03:07:23AM +0000, Liu, Yi L wrote:
> > > > It's not so explicit though. Perhaps worth to have a check like below in this patch?
> > > >
> > > > if (unlikely(klen > sizeof(union ucmd_buffer)))
> > > >   return -EINVAL;
> > >
> > > Yes, stick this in the domain allocate path with a WARN_ON. The driver
> > > is broken to allocate a domain with an invalid size.
> >
> > And here too with a WARN_ON_ONCE.
> >
> > +       /*
> > +        * Either the driver is broken by having an invalid size, or the user
> > +        * invalidate data struct used by the driver is missing in the union.
> > +        */
> > +       if (WARN_ON_ONCE(hwpt->domain->ops->cache_invalidate_user &&
> > +                        (!hwpt->domain->ops->cache_invalidate_user_data_len ||
> > +                         hwpt->domain->ops->cache_invalidate_user_data_len >
> > +                         sizeof(union ucmd_buffer)))) {
> > +               rc = -EINVAL;
> > +               goto out_abort;
> > +
> > +       }
> >
> > Though I am making this cache_invalidate_user optional here, I
> > wonder if there actually could be a case that a user-managed
> > domain doesn't need a cache_invalidate_user op...
> 
> If user-managed domain is the stage-1 domain in nested, then seems not
> possible as cache invalidate is a must. But I think this logic is fine as not
> all the domains allocated by the user is user-managed. It may be kernel
> managed like the s2 domains.

Oh, I forgot to mention that this piece is in the user-managed
HWPT allocator, following Jason's suggestion to separate them.

So, perhaps should just mark it mandatory:

+	if (WARN_ON_ONCE(!hwpt->domain->ops->cache_invalidate_user ||
+			 !hwpt->domain->ops->cache_invalidate_user_data_len ||
+			 hwpt->domain->ops->cache_invalidate_user_data_len >
+			 sizeof(union iommu_user_cache_invalidate))) {
+		rc = -EINVAL;
+		goto out_abort;
+	}