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Date:   Fri, 27 Mar 2020 10:28:50 -0700
From:   Jacob Pan <jacob.jun.pan@linux.intel.com>
To:     "Tian, Kevin" <kevin.tian@intel.com>
Cc:     Joerg Roedel <joro@8bytes.org>,
        Alex Williamson <alex.williamson@redhat.com>,
        Lu Baolu <baolu.lu@linux.intel.com>,
        "iommu@lists.linux-foundation.org" <iommu@lists.linux-foundation.org>,
        LKML <linux-kernel@vger.kernel.org>,
        David Woodhouse <dwmw2@infradead.org>,
        Jean-Philippe Brucker <jean-philippe@linaro.com>,
        "Liu, Yi L" <yi.l.liu@intel.com>,
        "Raj, Ashok" <ashok.raj@intel.com>,
        Christoph Hellwig <hch@infradead.org>,
        Jonathan Cameron <jic23@kernel.org>,
        Eric Auger <eric.auger@redhat.com>,
        jacob.jun.pan@linux.intel.com
Subject: Re: [PATCH 05/10] iommu/ioasid: Create an IOASID set for host SVA
 use
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On Fri, 27 Mar 2020 09:41:55 +0000
"Tian, Kevin" <kevin.tian@intel.com> wrote:

> > From: Jacob Pan <jacob.jun.pan@linux.intel.com>
> > 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@arm.com/#t	

In that case, use INVALID_IOASID_SET to indicate the search is global.
e.g.
ioasid_find(INVALID_IOASID_SET, data->hpasid, NULL);

> > 
> > 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@linux.intel.com>
> > ---
> >  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]