linux-kernel - Re: [PATCH v5 3/5] vfio/iommu_type1: Remove the domain->ops comparison

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Message-ID: <YuQZ84dsHASENfmM@nvidia.com>
Date:   Fri, 29 Jul 2022 14:33:39 -0300
From:   Jason Gunthorpe <jgg@...dia.com>
To:     Nicolin Chen <nicolinc@...dia.com>
Cc:     joro@...tes.org, will@...nel.org, marcan@...can.st,
        sven@...npeter.dev, robin.murphy@....com, robdclark@...il.com,
        baolu.lu@...ux.intel.com, orsonzhai@...il.com,
        baolin.wang7@...il.com, zhang.lyra@...il.com,
        jean-philippe@...aro.org, alex.williamson@...hat.com,
        kevin.tian@...el.com, suravee.suthikulpanit@....com,
        alyssa@...enzweig.io, dwmw2@...radead.org, mjrosato@...ux.ibm.com,
        gerald.schaefer@...ux.ibm.com, thierry.reding@...il.com,
        vdumpa@...dia.com, jonathanh@...dia.com, cohuck@...hat.com,
        thunder.leizhen@...wei.com, christophe.jaillet@...adoo.fr,
        chenxiang66@...ilicon.com, john.garry@...wei.com,
        yangyingliang@...wei.com, iommu@...ts.linux-foundation.org,
        iommu@...ts.linux.dev, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-arm-msm@...r.kernel.org, linux-s390@...r.kernel.org,
        linux-tegra@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, kvm@...r.kernel.org
Subject: Re: [PATCH v5 3/5] vfio/iommu_type1: Remove the domain->ops
 comparison

On Fri, Jul 01, 2022 at 02:44:53PM -0700, Nicolin Chen wrote:
> The domain->ops validation was added, as a precaution, for mixed-driver
> systems.
> 
> Per Robin's remarks,
> * While bus_set_iommu() still exists, the core code prevents multiple
>   drivers from registering, so we can't really run into a situation of
>   having a mixed-driver system:
>   https://lore.kernel.org/kvm/6e1280c5-4b22-ebb3-3912-6c72bc169982@arm.com/
> 
> * And there's plenty more significant problems than this to fix; in future
>   when many can be permitted, we will rely on the IOMMU core code to check
>   the domain->ops:
>   https://lore.kernel.org/kvm/6575de6d-94ba-c427-5b1e-967750ddff23@arm.com/
> 
> So remove the check in VFIO for simplicity.
> 
> Reviewed-by: Kevin Tian <kevin.tian@...el.com>
> Signed-off-by: Nicolin Chen <nicolinc@...dia.com>
> ---
>  drivers/vfio/vfio_iommu_type1.c | 32 +++++++++++---------------------
>  1 file changed, 11 insertions(+), 21 deletions(-)

Reviewed-by: Jason Gunthorpe <jgg@...dia.com>

Jason