Messages in this thread | | | Date | Wed, 1 Apr 2020 15:45:52 +0200 | From | Jean-Philippe Brucker <> | Subject | Re: [PATCH 01/10] iommu/ioasid: Introduce system-wide capacity |
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On Wed, Mar 25, 2020 at 10:55:22AM -0700, Jacob Pan wrote: > IOASID is a limited system-wide resource that can be allocated at > runtime. This limitation can be enumerated during boot. For example, on > x86 platforms, PCI Process Address Space ID (PASID) allocation uses > IOASID service. The number of supported PASID bits are enumerated by > extended capability register as defined in the VT-d spec. > > This patch adds a helper to set the system capacity, it expected to be > set during boot prior to any allocation request.
This one-time setting is a bit awkward. Since multiple IOMMU drivers may be loaded, this can't be a module_init() thing. And we generally have multiple SMMU instances in the system. So we'd need to call install_capacity() only for the first SMMU loaded with an arbitrary 1<<20, even though each SMMU can support different numbers of PASID bits. Furthermore, modules such as iommu-sva will want to initialize their IOASID set at module_init(), which will happen before the SMMU can set up the capacity, so ioasid_alloc_set() will return an error.
How about hardcoding ioasid_capacity to 20 bits for now? It's the PCIe limit and probably won't have to increase for a while.
Thanks, Jean
> > Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com> > --- > drivers/iommu/ioasid.c | 15 +++++++++++++++ > include/linux/ioasid.h | 5 ++++- > 2 files changed, 19 insertions(+), 1 deletion(-) > > diff --git a/drivers/iommu/ioasid.c b/drivers/iommu/ioasid.c > index 0f8dd377aada..4026e52855b9 100644 > --- a/drivers/iommu/ioasid.c > +++ b/drivers/iommu/ioasid.c > @@ -17,6 +17,21 @@ struct ioasid_data { > struct rcu_head rcu; > }; > > +static ioasid_t ioasid_capacity; > +static ioasid_t ioasid_capacity_avail; > + > +/* System capacity can only be set once */ > +void ioasid_install_capacity(ioasid_t total) > +{ > + if (ioasid_capacity) { > + pr_warn("IOASID capacity already set at %d\n", ioasid_capacity); > + return; > + } > + > + ioasid_capacity = ioasid_capacity_avail = total; > +} > +EXPORT_SYMBOL_GPL(ioasid_install_capacity); > + > /* > * 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 6f000d7a0ddc..9711fa0dc357 100644 > --- a/include/linux/ioasid.h > +++ b/include/linux/ioasid.h > @@ -40,7 +40,7 @@ void *ioasid_find(struct ioasid_set *set, ioasid_t ioasid, > int ioasid_register_allocator(struct ioasid_allocator_ops *allocator); > void ioasid_unregister_allocator(struct ioasid_allocator_ops *allocator); > int ioasid_set_data(ioasid_t ioasid, void *data); > - > +void ioasid_install_capacity(ioasid_t total); > #else /* !CONFIG_IOASID */ > static inline ioasid_t ioasid_alloc(struct ioasid_set *set, ioasid_t min, > ioasid_t max, void *private) > @@ -72,5 +72,8 @@ static inline int ioasid_set_data(ioasid_t ioasid, void *data) > return -ENOTSUPP; > } > > +static inline void ioasid_install_capacity(ioasid_t total) > +{ > +} > #endif /* CONFIG_IOASID */ > #endif /* __LINUX_IOASID_H */ > -- > 2.7.4 >
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