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