RE: [PATCH 05/10] iommu/ioasid: Create an IOASID set for host SVA use

[Tian, Kevin]

> From: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
> Sent: Saturday, March 28, 2020 1:29 AM
> 
> On Fri, 27 Mar 2020 09:41:55 +0000
> "Tian, Kevin" <kevin.tian@xxxxxxxxx> wrote:
> 
> > > From: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
> > > Sent: Thursday, March 26, 2020 1:55 AM
> > >
> > > Bare metal SVA allocates IOASIDs for native process addresses. This
> > > should be separated from VM allocated IOASIDs thus under its own
> > > set.
> >
> > A curious question. Now bare metal SVA uses the system set and guest
> > SVA uses dynamically-created set. Then do we still allow ioasid_alloc
> > with a NULL set pointer?
> >
> Good point! There shouldn't be NULL set. That was one of the sticky
> point in the previous allocation API. I will add a check in
> ioasid_alloc_set().
> 
> However, there is still need for global search, e.g. PRS.
> https://lore.kernel.org/linux-arm-kernel/1d62b2e1-fe8c-066d-34e0-
> f7929f6a78e2@xxxxxxx/#t
> 
> In that case, use INVALID_IOASID_SET to indicate the search is global.
> e.g.
> ioasid_find(INVALID_IOASID_SET, data->hpasid, NULL);

ok, it makes sense.

> 
> > >
> > > This patch creates a system IOASID set with its quota set to
> > > PID_MAX. This is a reasonable default in that SVM capable devices
> > > can only bind to limited user processes.
> > >
> > > Signed-off-by: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
> > > ---
> > >  drivers/iommu/intel-iommu.c | 8 +++++++-
> > >  drivers/iommu/ioasid.c      | 9 +++++++++
> > >  include/linux/ioasid.h      | 9 +++++++++
> > >  3 files changed, 25 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/iommu/intel-iommu.c
> > > b/drivers/iommu/intel-iommu.c index ec3fc121744a..af7a1ef7b31e
> > > 100644 --- a/drivers/iommu/intel-iommu.c
> > > +++ b/drivers/iommu/intel-iommu.c
> > > @@ -3511,8 +3511,14 @@ static int __init init_dmars(void)
> > >  		goto free_iommu;
> > >
> > >  	/* PASID is needed for scalable mode irrespective to SVM */
> > > -	if (intel_iommu_sm)
> > > +	if (intel_iommu_sm) {
> > >  		ioasid_install_capacity(intel_pasid_max_id);
> > > +		/* We should not run out of IOASIDs at boot */
> > > +		if (ioasid_alloc_system_set(PID_MAX_DEFAULT)) {
> > > +			pr_err("Failed to enable host PASID
> > > allocator\n");
> > > +			intel_iommu_sm = 0;
> > > +		}
> > > +	}
> > >
> > >  	/*
> > >  	 * for each drhd
> > > diff --git a/drivers/iommu/ioasid.c b/drivers/iommu/ioasid.c
> > > index 6265d2dbbced..9135af171a7c 100644
> > > --- a/drivers/iommu/ioasid.c
> > > +++ b/drivers/iommu/ioasid.c
> > > @@ -39,6 +39,9 @@ struct ioasid_data {
> > >  static ioasid_t ioasid_capacity;
> > >  static ioasid_t ioasid_capacity_avail;
> > >
> > > +int system_ioasid_sid;
> > > +static DECLARE_IOASID_SET(system_ioasid);
> > > +
> > >  /* System capacity can only be set once */
> > >  void ioasid_install_capacity(ioasid_t total)
> > >  {
> > > @@ -51,6 +54,12 @@ void ioasid_install_capacity(ioasid_t total)
> > >  }
> > >  EXPORT_SYMBOL_GPL(ioasid_install_capacity);
> > >
> > > +int ioasid_alloc_system_set(int quota)
> > > +{
> > > +	return ioasid_alloc_set(&system_ioasid, quota,
> > > &system_ioasid_sid); +}
> > > +EXPORT_SYMBOL_GPL(ioasid_alloc_system_set);
> > > +
> > >  /*
> > >   * struct ioasid_allocator_data - Internal data structure to hold
> > > information
> > >   * about an allocator. There are two types of allocators:
> > > diff --git a/include/linux/ioasid.h b/include/linux/ioasid.h
> > > index 8c82d2625671..097b1cc043a3 100644
> > > --- a/include/linux/ioasid.h
> > > +++ b/include/linux/ioasid.h
> > > @@ -29,6 +29,9 @@ struct ioasid_allocator_ops {
> > >  	void *pdata;
> > >  };
> > >
> > > +/* Shared IOASID set for reserved for host system use */
> > > +extern int system_ioasid_sid;
> > > +
> > >  #define DECLARE_IOASID_SET(name) struct ioasid_set name = { 0 }
> > >
> > >  #if IS_ENABLED(CONFIG_IOASID)
> > > @@ -41,6 +44,7 @@ int ioasid_register_allocator(struct
> > > ioasid_allocator_ops *allocator);
> > >  void ioasid_unregister_allocator(struct ioasid_allocator_ops
> > > *allocator); int ioasid_attach_data(ioasid_t ioasid, void *data);
> > >  void ioasid_install_capacity(ioasid_t total);
> > > +int ioasid_alloc_system_set(int quota);
> > >  int ioasid_alloc_set(struct ioasid_set *token, ioasid_t quota, int
> > > *sid); void ioasid_free_set(int sid, bool destroy_set);
> > >  int ioasid_find_sid(ioasid_t ioasid);
> > > @@ -88,5 +92,10 @@ static inline void
> > > ioasid_install_capacity(ioasid_t total) {
> > >  }
> > >
> > > +static inline int ioasid_alloc_system_set(int quota)
> > > +{
> > > +	return -ENOTSUPP;
> > > +}
> > > +
> > >  #endif /* CONFIG_IOASID */
> > >  #endif /* __LINUX_IOASID_H */
> > > --
> > > 2.7.4
> >
> 
> [Jacob Pan]