linux-kernel - Re: [PATCH v7 10/28] iommufd/access: Bypass access->ops->unmap for internal use

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Message-ID: <aGWSkRX4yUuuOVZ8@Asurada-Nvidia>
Date: Wed, 2 Jul 2025 13:12:01 -0700
From: Nicolin Chen <nicolinc@...dia.com>
To: "Tian, Kevin" <kevin.tian@...el.com>
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Subject: Re: [PATCH v7 10/28] iommufd/access: Bypass access->ops->unmap for
 internal use

On Wed, Jul 02, 2025 at 09:45:26AM +0000, Tian, Kevin wrote:
> > From: Nicolin Chen <nicolinc@...dia.com>
> > Sent: Friday, June 27, 2025 3:35 AM
> > 
> > +int iommufd_access_notify_unmap(struct io_pagetable *iopt, unsigned long
> > iova,
> > +				unsigned long length)
> >  {
> >  	struct iommufd_ioas *ioas =
> >  		container_of(iopt, struct iommufd_ioas, iopt);
> >  	struct iommufd_access *access;
> >  	unsigned long index;
> > +	int ret = 0;
> > 
> >  	xa_lock(&ioas->iopt.access_list);
> > +	/* Bypass any unmap if there is an internal access */
> > +	xa_for_each(&ioas->iopt.access_list, index, access) {
> > +		if (iommufd_access_is_internal(access)) {
> > +			ret = -EBUSY;
> > +			goto unlock;
> > +		}
> > +	}
> > +
> 
> hmm all those checks are per iopt. Could do one-off check in
> iopt_unmap_iova_range() and store the result in a local flag.
> 
> Then use that flag to decide whether to return -EBUSY if
> area->num_accesses is true in the loop.

I don't quite follow this...

Do you suggest to move this xa_for_each to iopt_unmap_iova_range?

What's that local flag used for?

Thanks
Nicolin