linux-kernel - Re: [PATCH v2 3/6] iommu: Same critical region for device release and removal

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Date:   Mon, 20 Feb 2023 21:13:07 -0400
From:   Jason Gunthorpe <jgg@...dia.com>
To:     Baolu Lu <baolu.lu@...ux.intel.com>
Cc:     iommu@...ts.linux.dev, Joerg Roedel <joro@...tes.org>,
        Christoph Hellwig <hch@...radead.org>,
        Kevin Tian <kevin.tian@...el.com>,
        Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 3/6] iommu: Same critical region for device release
 and removal

On Sat, Feb 18, 2023 at 03:29:12PM +0800, Baolu Lu wrote:
> On 2/17/23 11:40 PM, Jason Gunthorpe wrote:
> > On Fri, Feb 17, 2023 at 05:47:33PM +0800, Lu Baolu wrote:
> > > In a non-driver context, it is crucial to ensure the consistency of a
> > > device's iommu ops. Otherwise, it may result in a situation where a
> > > device is released but it's iommu ops are still used.
> > > 
> > > Put the ops->release_device and __iommu_group_remove_device() in a some
> > > group->mutext critical region, so that, as long as group->mutex is held
> > > and the device is in its group's device list, its iommu ops are always
> > > consistent.
> > > 
> > > Signed-off-by: Lu Baolu<baolu.lu@...ux.intel.com>
> > > ---
> > >   drivers/iommu/iommu.c | 15 +++++++++++++--
> > >   1 file changed, 13 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> > > index 6247883991e2..093692308b80 100644
> > > --- a/drivers/iommu/iommu.c
> > > +++ b/drivers/iommu/iommu.c
> > > @@ -101,6 +101,10 @@ static int iommu_create_device_direct_mappings(struct iommu_group *group,
> > >   static struct iommu_group *iommu_group_get_for_dev(struct device *dev);
> > >   static ssize_t iommu_group_store_type(struct iommu_group *group,
> > >   				      const char *buf, size_t count);
> > > +static struct group_device *
> > > +__iommu_group_remove_device(struct iommu_group *group, struct device *dev);
> > > +static void __iommu_group_release_device(struct iommu_group *group,
> > > +					 struct group_device *grp_dev);
> > Seems like a hunk is missing from this patch?
> 
> Did you mean below block of change? If so, I will add it in the next
> version.

I  mean this changed the protoype but I didn't see a change in the
actual funtion?

> By the way, can I add you signed-off-by when I use the code you posted
> in the discussion thread?

Yes

Jason