On Mon, 10 Jun 2019 19:47:07 +0100 Jean-Philippe Brucker <jean-philippe.brucker@xxxxxxx> wrote: > Some devices might support multiple DMA address spaces, in particular > those that have the PCI PASID feature. PASID (Process Address Space > ID) allows to share process address spaces with devices (SVA), > partition a device into VM-assignable entities (VFIO mdev) or simply > provide multiple DMA address space to kernel drivers. Add a global > PASID allocator usable by different drivers at the same time. Name it > I/O ASID to avoid confusion with ASIDs allocated by arch code, which > are usually a separate ID space. > > The IOASID space is global. Each device can have its own PASID space, > but by convention the IOMMU ended up having a global PASID space, so > that with SVA, each mm_struct is associated to a single PASID. > > The allocator is primarily used by IOMMU subsystem but in rare > occasions drivers would like to allocate PASIDs for devices that > aren't managed by an IOMMU, using the same ID space as IOMMU. > > Signed-off-by: Jean-Philippe Brucker <jean-philippe.brucker@xxxxxxx> > Signed-off-by: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx> > --- > The most recent discussion on this patch was at: > https://lkml.kernel.org/lkml/1556922737-76313-4-git-send-email-jacob.jun.pan@xxxxxxxxxxxxxxx/ > I fixed it up a bit following comments in that series, and removed the > definitions for the custom allocator for now. > > There also is a new version that includes the custom allocator into > this patch, but is currently missing the RCU fixes, at: > https://lore.kernel.org/lkml/1560087862-57608-13-git-send-email-jacob.jun.pan@xxxxxxxxxxxxxxx/ > --- > drivers/iommu/Kconfig | 4 ++ > drivers/iommu/Makefile | 1 + > drivers/iommu/ioasid.c | 150 > +++++++++++++++++++++++++++++++++++++++++ include/linux/ioasid.h | > 49 ++++++++++++++ 4 files changed, 204 insertions(+) > create mode 100644 drivers/iommu/ioasid.c > create mode 100644 include/linux/ioasid.h > > diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig > index 83664db5221d..9b45f70549a7 100644 > --- a/drivers/iommu/Kconfig > +++ b/drivers/iommu/Kconfig > @@ -3,6 +3,10 @@ > config IOMMU_IOVA > tristate > > +# The IOASID library may also be used by non-IOMMU_API users > +config IOASID > + tristate > + > # IOMMU_API always gets selected by whoever wants it. > config IOMMU_API > bool > diff --git a/drivers/iommu/Makefile b/drivers/iommu/Makefile > index 8c71a15e986b..0efac6f1ec73 100644 > --- a/drivers/iommu/Makefile > +++ b/drivers/iommu/Makefile > @@ -7,6 +7,7 @@ obj-$(CONFIG_IOMMU_DMA) += dma-iommu.o > obj-$(CONFIG_IOMMU_IO_PGTABLE) += io-pgtable.o > obj-$(CONFIG_IOMMU_IO_PGTABLE_ARMV7S) += io-pgtable-arm-v7s.o > obj-$(CONFIG_IOMMU_IO_PGTABLE_LPAE) += io-pgtable-arm.o > +obj-$(CONFIG_IOASID) += ioasid.o > obj-$(CONFIG_IOMMU_IOVA) += iova.o > obj-$(CONFIG_OF_IOMMU) += of_iommu.o > obj-$(CONFIG_MSM_IOMMU) += msm_iommu.o > diff --git a/drivers/iommu/ioasid.c b/drivers/iommu/ioasid.c > new file mode 100644 > index 000000000000..bbb771214fa9 > --- /dev/null > +++ b/drivers/iommu/ioasid.c > @@ -0,0 +1,150 @@ > +// SPDX-License-Identifier: GPL-2.0 > +/* > + * I/O Address Space ID allocator. There is one global IOASID space, > split into > + * subsets. Users create a subset with DECLARE_IOASID_SET, then > allocate and > + * free IOASIDs with ioasid_alloc and ioasid_free. > + */ > +#include <linux/ioasid.h> > +#include <linux/module.h> > +#include <linux/slab.h> > +#include <linux/spinlock.h> > +#include <linux/xarray.h> > + > +struct ioasid_data { > + ioasid_t id; > + struct ioasid_set *set; > + void *private; > + struct rcu_head rcu; > +}; > + > +static DEFINE_XARRAY_ALLOC(ioasid_xa); > + > +/** > + * ioasid_set_data - Set private data for an allocated ioasid > + * @ioasid: the ID to set data > + * @data: the private data > + * > + * For IOASID that is already allocated, private data can be set > + * via this API. Future lookup can be done via ioasid_find. > + */ > +int ioasid_set_data(ioasid_t ioasid, void *data) > +{ > + struct ioasid_data *ioasid_data; > + int ret = 0; > + > + xa_lock(&ioasid_xa); Just wondering if this is necessary, since xa_load is under rcu_read_lock and we are not changing anything internal to xa. For custom allocator I still need to have the mutex against allocator removal. > + ioasid_data = xa_load(&ioasid_xa, ioasid); > + if (ioasid_data) > + rcu_assign_pointer(ioasid_data->private, data); it is good to publish and have barrier here. But I just wonder even for weakly ordered machine, this pointer update is quite far away from its data update. > + else > + ret = -ENOENT; > + xa_unlock(&ioasid_xa); > + > + /* > + * Wait for readers to stop accessing the old private data, > so the > + * caller can free it. > + */ > + if (!ret) > + synchronize_rcu(); > + I will add that to my next version to check ret value. Thanks, Jacob > + return ret; > +} > +EXPORT_SYMBOL_GPL(ioasid_set_data); > + > +/** > + * ioasid_alloc - Allocate an IOASID > + * @set: the IOASID set > + * @min: the minimum ID (inclusive) > + * @max: the maximum ID (inclusive) > + * @private: data private to the caller > + * > + * Allocate an ID between @min and @max. The @private pointer is > stored > + * internally and can be retrieved with ioasid_find(). > + * > + * Return: the allocated ID on success, or %INVALID_IOASID on > failure. > + */ > +ioasid_t ioasid_alloc(struct ioasid_set *set, ioasid_t min, ioasid_t > max, > + void *private) > +{ > + u32 id = INVALID_IOASID; > + struct ioasid_data *data; > + > + data = kzalloc(sizeof(*data), GFP_KERNEL); > + if (!data) > + return INVALID_IOASID; > + > + data->set = set; > + data->private = private; > + > + if (xa_alloc(&ioasid_xa, &id, data, XA_LIMIT(min, max), > GFP_KERNEL)) { > + pr_err("Failed to alloc ioasid from %d to %d\n", > min, max); > + goto exit_free; > + } > + data->id = id; > + > +exit_free: > + if (id == INVALID_IOASID) { > + kfree(data); > + return INVALID_IOASID; > + } > + return id; > +} > +EXPORT_SYMBOL_GPL(ioasid_alloc); > + > +/** > + * ioasid_free - Free an IOASID > + * @ioasid: the ID to remove > + */ > +void ioasid_free(ioasid_t ioasid) > +{ > + struct ioasid_data *ioasid_data; > + > + ioasid_data = xa_erase(&ioasid_xa, ioasid); > + > + kfree_rcu(ioasid_data, rcu); > +} > +EXPORT_SYMBOL_GPL(ioasid_free); > + > +/** > + * ioasid_find - Find IOASID data > + * @set: the IOASID set > + * @ioasid: the IOASID to find > + * @getter: function to call on the found object > + * > + * The optional getter function allows to take a reference to the > found object > + * under the rcu lock. The function can also check if the object is > still valid: > + * if @getter returns false, then the object is invalid and NULL is > returned. > + * > + * If the IOASID has been allocated for this set, return the private > pointer > + * passed to ioasid_alloc. Private data can be NULL if not set. > Return an error > + * if the IOASID is not found or does not belong to the set. > + */ > +void *ioasid_find(struct ioasid_set *set, ioasid_t ioasid, > + bool (*getter)(void *)) > +{ > + void *priv = NULL; > + struct ioasid_data *ioasid_data; > + > + rcu_read_lock(); > + ioasid_data = xa_load(&ioasid_xa, ioasid); > + if (!ioasid_data) { > + priv = ERR_PTR(-ENOENT); > + goto unlock; > + } > + if (set && ioasid_data->set != set) { > + /* data found but does not belong to the set */ > + priv = ERR_PTR(-EACCES); > + goto unlock; > + } > + /* Now IOASID and its set is verified, we can return the > private data */ > + priv = rcu_dereference(ioasid_data->private); > + if (getter && !getter(priv)) > + priv = NULL; > +unlock: > + rcu_read_unlock(); > + > + return priv; > +} > +EXPORT_SYMBOL_GPL(ioasid_find); > + > +MODULE_LICENSE("GPL"); > diff --git a/include/linux/ioasid.h b/include/linux/ioasid.h > new file mode 100644 > index 000000000000..940212422b8f > --- /dev/null > +++ b/include/linux/ioasid.h > @@ -0,0 +1,49 @@ > +/* SPDX-License-Identifier: GPL-2.0 */ > +#ifndef __LINUX_IOASID_H > +#define __LINUX_IOASID_H > + > +#include <linux/types.h> > + > +#define INVALID_IOASID ((ioasid_t)-1) > +typedef unsigned int ioasid_t; > + > +struct ioasid_set { > + int dummy; > +}; > + > +#define DECLARE_IOASID_SET(name) struct ioasid_set name = { 0 } > + > +#if IS_ENABLED(CONFIG_IOASID) > +ioasid_t ioasid_alloc(struct ioasid_set *set, ioasid_t min, ioasid_t > max, > + void *private); > +void ioasid_free(ioasid_t ioasid); > + > +void *ioasid_find(struct ioasid_set *set, ioasid_t ioasid, > + bool (*getter)(void *)); > + > +int ioasid_set_data(ioasid_t ioasid, void *data); > + > +#else /* !CONFIG_IOASID */ > +static inline ioasid_t ioasid_alloc(struct ioasid_set *set, ioasid_t > min, > + ioasid_t max, void *private) > +{ > + return INVALID_IOASID; > +} > + > +static inline void ioasid_free(ioasid_t ioasid) > +{ > +} > + > +static inline void *ioasid_find(struct ioasid_set *set, ioasid_t > ioasid, > + bool (*getter)(void *)) > +{ > + return NULL; > +} > + > +static inline int ioasid_set_data(ioasid_t ioasid, void *data) > +{ > + return -ENODEV; > +} > + > +#endif /* CONFIG_IOASID */ > +#endif /* __LINUX_IOASID_H */ [Jacob Pan]
