linux-kernel - Re: [PATCH v1 14/14] iommu/arm-smmu-v3: Add arm_smmu_cache_invalidate

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Message-ID: <ZBh7hSX5hdW4vxwh@Asurada-Nvidia>
Date:   Mon, 20 Mar 2023 08:28:05 -0700
From:   Nicolin Chen <nicolinc@...dia.com>
To:     Jason Gunthorpe <jgg@...dia.com>
CC:     Robin Murphy <robin.murphy@....com>, <will@...nel.org>,
        <eric.auger@...hat.com>, <kevin.tian@...el.com>,
        <baolu.lu@...ux.intel.com>, <joro@...tes.org>,
        <shameerali.kolothum.thodi@...wei.com>, <jean-philippe@...aro.org>,
        <linux-arm-kernel@...ts.infradead.org>, <iommu@...ts.linux.dev>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1 14/14] iommu/arm-smmu-v3: Add
 arm_smmu_cache_invalidate_user

On Mon, Mar 20, 2023 at 10:11:54AM -0300, Jason Gunthorpe wrote:
> On Sun, Mar 19, 2023 at 06:32:03PM -0700, Nicolin Chen wrote:
> 
> > +struct iommu_hwpt_invalidate_arm_smmuv3 {
> > +       struct iommu_iova_range range;
> 
> what is this?

Not used. A copy-n-paste mistake :(

> 
> > +       __u64 cmd[2];
> > +};
> 
> You still have to do something with the SID. We can't just allow any
> un-validated SID value - the driver has to check the incoming SID
> against allowed SIDs for this iommufd_ctx

Hmm, that's something "missing" even in the current design.

Yet, most of the TLBI commands don't hold an SID field. So,
the hypervisor only trapping a queue write-pointer movement
cannot get the exact vSID for a TLBI command. What our QEMU
code currently does is simply broadcasting all the devices
on the list of attaching devices to the vSMMU, which means
that such an enforcement in the kernel would basically just
allow any vSID (device) that's attached to the domain?

Thanks
Nic