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Message-ID: <6A3DF150A5B70D4F9B66A25E3F7C888D0718FDC3@039-SN2MPN1-011.039d.mgd.msft.net>
Date: Fri, 4 Oct 2013 10:42:23 +0000
From: Bhushan Bharat-R65777 <R65777@...escale.com>
To: Bhushan Bharat-R65777 <R65777@...escale.com>,
Alex Williamson <alex.williamson@...hat.com>
CC: "joro@...tes.org" <joro@...tes.org>,
"benh@...nel.crashing.org" <benh@...nel.crashing.org>,
"galak@...nel.crashing.org" <galak@...nel.crashing.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
"agraf@...e.de" <agraf@...e.de>,
Wood Scott-B07421 <B07421@...escale.com>,
"iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>
Subject: RE: [PATCH 2/7] iommu: add api to get iommu_domain of a device
> -----Original Message-----
> From: Bhushan Bharat-R65777
> Sent: Friday, October 04, 2013 3:24 PM
> To: 'Alex Williamson'
> Cc: joro@...tes.org; benh@...nel.crashing.org; galak@...nel.crashing.org; linux-
> kernel@...r.kernel.org; linuxppc-dev@...ts.ozlabs.org; linux-
> pci@...r.kernel.org; agraf@...e.de; Wood Scott-B07421; iommu@...ts.linux-
> foundation.org
> Subject: RE: [PATCH 2/7] iommu: add api to get iommu_domain of a device
>
>
>
> > -----Original Message-----
> > From: linux-pci-owner@...r.kernel.org
> > [mailto:linux-pci-owner@...r.kernel.org]
> > On Behalf Of Alex Williamson
> > Sent: Wednesday, September 25, 2013 10:16 PM
> > To: Bhushan Bharat-R65777
> > Cc: joro@...tes.org; benh@...nel.crashing.org;
> > galak@...nel.crashing.org; linux- kernel@...r.kernel.org;
> > linuxppc-dev@...ts.ozlabs.org; linux- pci@...r.kernel.org;
> > agraf@...e.de; Wood Scott-B07421; iommu@...ts.linux- foundation.org;
> > Bhushan Bharat-R65777
> > Subject: Re: [PATCH 2/7] iommu: add api to get iommu_domain of a
> > device
> >
> > On Thu, 2013-09-19 at 12:59 +0530, Bharat Bhushan wrote:
> > > This api return the iommu domain to which the device is attached.
> > > The iommu_domain is required for making API calls related to iommu.
> > > Follow up patches which use this API to know iommu maping.
> > >
> > > Signed-off-by: Bharat Bhushan <bharat.bhushan@...escale.com>
> > > ---
> > > drivers/iommu/iommu.c | 10 ++++++++++
> > > include/linux/iommu.h | 7 +++++++
> > > 2 files changed, 17 insertions(+), 0 deletions(-)
> > >
> > > diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c index
> > > fbe9ca7..6ac5f50 100644
> > > --- a/drivers/iommu/iommu.c
> > > +++ b/drivers/iommu/iommu.c
> > > @@ -696,6 +696,16 @@ void iommu_detach_device(struct iommu_domain
> > > *domain, struct device *dev) }
> > > EXPORT_SYMBOL_GPL(iommu_detach_device);
> > >
> > > +struct iommu_domain *iommu_get_dev_domain(struct device *dev) {
> > > + struct iommu_ops *ops = dev->bus->iommu_ops;
> > > +
> > > + if (unlikely(ops == NULL || ops->get_dev_iommu_domain == NULL))
> > > + return NULL;
> > > +
> > > + return ops->get_dev_iommu_domain(dev); }
> > > +EXPORT_SYMBOL_GPL(iommu_get_dev_domain);
> >
> > What prevents this from racing iommu_domain_free()? There's no
> > references acquired, so there's no reason for the caller to assume the pointer
> is valid.
>
> Sorry for late query, somehow this email went into a folder and escaped;
>
> Just to be sure, there is not lock at generic "struct iommu_domain", but IP
> specific structure (link FSL domain) linked in iommu_domain->priv have a lock,
> so we need to ensure this race in FSL iommu code (say
> drivers/iommu/fsl_pamu_domain.c), right?
Further thinking of this, there are more problems here:
- Like MSI subsystem will call iommu_get_dev_domain(), which will take a lock, find the domain pointer, release the lock, and return the domain
- Now if domain in freed up
- While MSI subsystem tries to do work on domain (like get_attribute/set_attribute etc) ???
So can we do like iommu_get_dev_domain() will return domain with the lock held, and iommu_put_dev_domain() will release the lock? And iommu_get_dev_domain() must always be followed by iommu_get_dev_domain()
Thanks
-Bharat
>
> Thanks
> -Bharat
>
> >
> > > /*
> > > * IOMMU groups are really the natrual working unit of the IOMMU, but
> > > * the IOMMU API works on domains and devices. Bridge that gap by
> > > diff --git a/include/linux/iommu.h b/include/linux/iommu.h index
> > > 7ea319e..fa046bd 100644
> > > --- a/include/linux/iommu.h
> > > +++ b/include/linux/iommu.h
> > > @@ -127,6 +127,7 @@ struct iommu_ops {
> > > int (*domain_set_windows)(struct iommu_domain *domain, u32 w_count);
> > > /* Get the numer of window per domain */
> > > u32 (*domain_get_windows)(struct iommu_domain *domain);
> > > + struct iommu_domain *(*get_dev_iommu_domain)(struct device *dev);
> > >
> > > unsigned long pgsize_bitmap;
> > > };
> > > @@ -190,6 +191,7 @@ extern int iommu_domain_window_enable(struct
> > > iommu_domain
> > *domain, u32 wnd_nr,
> > > phys_addr_t offset, u64 size,
> > > int prot);
> > > extern void iommu_domain_window_disable(struct iommu_domain
> > > *domain,
> > > u32 wnd_nr);
> > > +extern struct iommu_domain *iommu_get_dev_domain(struct device
> > > +*dev);
> > > /**
> > > * report_iommu_fault() - report about an IOMMU fault to the IOMMU
> framework
> > > * @domain: the iommu domain where the fault has happened @@ -284,6
> > > +286,11 @@ static inline void iommu_domain_window_disable(struct
> > > iommu_domain *domain, { }
> > >
> > > +static inline struct iommu_domain *iommu_get_dev_domain(struct
> > > +device
> > > +*dev) {
> > > + return NULL;
> > > +}
> > > +
> > > static inline phys_addr_t iommu_iova_to_phys(struct iommu_domain
> > > *domain, dma_addr_t iova) {
> > > return 0;
> >
> >
> >
> > --
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> > info at http://vger.kernel.org/majordomo-info.html
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