Re: [RFC PATCH 2/7] iommu: Add share domain interface in iommu for spimdev

[Kenneth Lee <liguozhu-C8/M+/jPZTeaMJb+Lgu22Q@public.gmane.org>]

On Thu, Aug 02, 2018 at 03:17:03AM +0000, Tian, Kevin wrote:
> Date: Thu, 2 Aug 2018 03:17:03 +0000
> From: "Tian, Kevin" <kevin.tian@intel.com>
> To: Kenneth Lee <nek.in.cn@gmail.com>, Jonathan Corbet <corbet@lwn.net>,
>  Herbert Xu <herbert@gondor.apana.org.au>, "David S . Miller"
>  <davem@davemloft.net>, Joerg Roedel <joro@8bytes.org>, Alex Williamson
>  <alex.williamson@redhat.com>, Kenneth Lee <liguozhu@hisilicon.com>, Hao
>  Fang <fanghao11@huawei.com>, Zhou Wang <wangzhou1@hisilicon.com>, Zaibo Xu
>  <xuzaibo@huawei.com>, Philippe Ombredanne <pombredanne@nexb.com>, Greg
>  Kroah-Hartman <gregkh@linuxfoundation.org>, Thomas Gleixner
>  <tglx@linutronix.de>, "linux-doc@vger.kernel.org"
>  <linux-doc@vger.kernel.org>, "linux-kernel@vger.kernel.org"
>  <linux-kernel@vger.kernel.org>, "linux-crypto@vger.kernel.org"
>  <linux-crypto@vger.kernel.org>, "iommu@lists.linux-foundation.org"
>  <iommu@lists.linux-foundation.org>, "kvm@vger.kernel.org"
>  <kvm@vger.kernel.org>, "linux-accelerators@lists.ozlabs.org"
>  <linux-accelerators@lists.ozlabs.org>, Lu Baolu
>  <baolu.lu@linux.intel.com>, "Kumar, Sanjay K" <sanjay.k.kumar@intel.com>
> CC: "linuxarm@huawei.com" <linuxarm@huawei.com>
> Subject: RE: [RFC PATCH 2/7] iommu: Add share domain interface in iommu for
>  spimdev
> Message-ID: <AADFC41AFE54684AB9EE6CBC0274A5D191290F49@SHSMSX101.ccr.corp.intel.com>
> 
> > From: Kenneth Lee
> > Sent: Wednesday, August 1, 2018 6:22 PM
> > 
> > From: Kenneth Lee <liguozhu@hisilicon.com>
> > 
> > This patch add sharing interface for a iommu_group. The new interface:
> > 
> > 	iommu_group_share_domain()
> > 	iommu_group_unshare_domain()
> > 
> > can be used by some virtual iommu_group (such as iommu_group for
> > spimdev)
> > to share their parent's iommu_group.
> > 
> > When the domain of the group is shared, it cannot be changed before
> > unshared.  In the future, notification can be added if update is required.
> 
> Is it necessary or just asking VFIO to use parent domain directly? 
> 
Even we add to VFIO, the iommu still need to be changed. We can move the type1
part to VFIO if we have agreement in RFC stage.
> > 
> > Signed-off-by: Kenneth Lee <liguozhu@hisilicon.com>
> > ---
> >  drivers/iommu/iommu.c | 28 +++++++++++++++++++++++++++-
> >  include/linux/iommu.h |  2 ++
> >  2 files changed, 29 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> > index 63b37563db7e..a832aafe660d 100644
> > --- a/drivers/iommu/iommu.c
> > +++ b/drivers/iommu/iommu.c
> > @@ -54,6 +54,9 @@ struct iommu_group {
> >  	int id;
> >  	struct iommu_domain *default_domain;
> >  	struct iommu_domain *domain;
> > +	atomic_t domain_shared_ref; /* Number of user of current domain.
> > +				     * The domain cannot be modified if ref >
> > 0
> > +				     */
> >  };
> > 
> >  struct group_device {
> > @@ -353,6 +356,7 @@ struct iommu_group *iommu_group_alloc(void)
> >  		return ERR_PTR(ret);
> >  	}
> >  	group->id = ret;
> > +	atomic_set(&group->domain_shared_ref, 0);
> > 
> >  	ret = kobject_init_and_add(&group->kobj, &iommu_group_ktype,
> >  				   NULL, "%d", group->id);
> > @@ -482,6 +486,25 @@ int iommu_group_set_name(struct iommu_group
> > *group, const char *name)
> >  }
> >  EXPORT_SYMBOL_GPL(iommu_group_set_name);
> > 
> > +struct iommu_domain *iommu_group_share_domain(struct
> > iommu_group *group)
> > +{
> > +	/* the domain can be shared only when the default domain is used
> > */
> > +	/* todo: more shareable check */
> > +	if (group->domain != group->default_domain)
> > +		return ERR_PTR(-EINVAL);
> > +
> > +	atomic_inc(&group->domain_shared_ref);
> > +	return group->domain;
> > +}
> > +EXPORT_SYMBOL_GPL(iommu_group_share_domain);
> > +
> > +void iommu_group_unshare_domain(struct iommu_group *group)
> > +{
> > +	atomic_dec(&group->domain_shared_ref);
> > +	WARN_ON(atomic_read(&group->domain_shared_ref) < 0);
> > +}
> > +EXPORT_SYMBOL_GPL(iommu_group_unshare_domain);
> > +
> >  static int iommu_group_create_direct_mappings(struct iommu_group
> > *group,
> >  					      struct device *dev)
> >  {
> > @@ -1401,7 +1424,8 @@ static int __iommu_attach_group(struct
> > iommu_domain *domain,
> >  {
> >  	int ret;
> > 
> > -	if (group->default_domain && group->domain != group-
> > >default_domain)
> > +	if ((group->default_domain && group->domain != group-
> > >default_domain) ||
> > +	     atomic_read(&group->domain_shared_ref) > 0)
> >  		return -EBUSY;
> > 
> >  	ret = __iommu_group_for_each_dev(group, domain,
> > @@ -1438,6 +1462,8 @@ static void __iommu_detach_group(struct
> > iommu_domain *domain,
> >  {
> >  	int ret;
> > 
> > +	WARN_ON(atomic_read(&group->domain_shared_ref) > 0);
> > +
> >  	if (!group->default_domain) {
> >  		__iommu_group_for_each_dev(group, domain,
> >  					   iommu_group_do_detach_device);
> > diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> > index 19938ee6eb31..278d60e3ec39 100644
> > --- a/include/linux/iommu.h
> > +++ b/include/linux/iommu.h
> > @@ -349,6 +349,8 @@ extern int iommu_domain_get_attr(struct
> > iommu_domain *domain, enum iommu_attr,
> >  				 void *data);
> >  extern int iommu_domain_set_attr(struct iommu_domain *domain, enum
> > iommu_attr,
> >  				 void *data);
> > +extern struct iommu_domain *iommu_group_share_domain(struct
> > iommu_group *group);
> > +extern void iommu_group_unshare_domain(struct iommu_group *group);
> > 
> >  /* Window handling function prototypes */
> >  extern int iommu_domain_window_enable(struct iommu_domain
> > *domain, u32 wnd_nr,
> > --
> > 2.17.1

-- 
			-Kenneth(Hisilicon)

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