[PATCH kernel v4 04/10] powerpc/vfio_spapr_tce: Add reference counting to iommu_table

Alexey Kardashevskiy
2017-02-07T07:17:39Z

So far iommu_table obejcts were only used in virtual mode and had
a single owner. We are going to change this by implementing in-kernel
acceleration of DMA mapping requests. The proposed acceleration
will handle requests in real mode and KVM will keep references to tables.

This adds a kref to iommu_table and defines new helpers to update it.
This replaces iommu_free_table() with iommu_table_put() and makes
iommu_free_table() static. iommu_table_get() is not used in this patch
but it will be in the following patch.

Since this touches prototypes, this also removes @node_name parameter as
it has never been really useful on powernv and carrying it for
the pseries platform code to iommu_free_table() seems to be quite
useless as well.

This should cause no behavioral change.

Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
---
arch/powerpc/include/asm/iommu.h | 5 +++--
arch/powerpc/kernel/iommu.c | 24 +++++++++++++++++++-----
arch/powerpc/platforms/powernv/pci-ioda.c | 14 +++++++-------
arch/powerpc/platforms/powernv/pci.c | 1 +
arch/powerpc/platforms/pseries/iommu.c | 3 ++-
arch/powerpc/platforms/pseries/vio.c | 2 +-
drivers/vfio/vfio_iommu_spapr_tce.c | 2 +-
7 files changed, 34 insertions(+), 17 deletions(-)

diff --git a/arch/powerpc/include/asm/iommu.h b/arch/powerpc/include/asm/iommu.h
index 4554699aec02..82e77ebf85f4 100644
--- a/arch/powerpc/include/asm/iommu.h
+++ b/arch/powerpc/include/asm/iommu.h
@@ -119,6 +119,7 @@ struct iommu_table {
struct list_head it_group_list;/* List of iommu_table_group_link */
unsigned long *it_userspace; /* userspace view of the table */
struct iommu_table_ops *it_ops;
+ struct kref it_kref;
};

#define IOMMU_TABLE_USERSPACE_ENTRY(tbl, entry) \
@@ -151,8 +152,8 @@ static inline void *get_iommu_table_base(struct device *dev)

extern int dma_iommu_dma_supported(struct device *dev, u64 mask);

-/* Frees table for an individual device node */
-extern void iommu_free_table(struct iommu_table *tbl, const char *node_name);
+extern void iommu_table_get(struct iommu_table *tbl);
+extern void iommu_table_put(struct iommu_table *tbl);

/* Initializes an iommu_table based in values set in the passed-in
* structure
diff --git a/arch/powerpc/kernel/iommu.c b/arch/powerpc/kernel/iommu.c
index bc142d87130f..d02b8d22fb50 100644
--- a/arch/powerpc/kernel/iommu.c
+++ b/arch/powerpc/kernel/iommu.c
@@ -711,13 +711,13 @@ struct iommu_table *iommu_init_table(struct iommu_table *tbl, int nid)
return tbl;
}

-void iommu_free_table(struct iommu_table *tbl, const char *node_name)
+static void iommu_table_free(struct kref *kref)
{
unsigned long bitmap_sz;
unsigned int order;
+ struct iommu_table *tbl;

- if (!tbl)
- return;
+ tbl = container_of(kref, struct iommu_table, it_kref);

if (tbl->it_ops->free)
tbl->it_ops->free(tbl);
@@ -736,7 +736,7 @@ void iommu_free_table(struct iommu_table *tbl, const char *node_name)

/* verify that table contains no entries */
if (!bitmap_empty(tbl->it_map, tbl->it_size))
- pr_warn("%s: Unexpected TCEs for %s\n", __func__, node_name);
+ pr_warn("%s: Unexpected TCEs\n", __func__);

/* calculate bitmap size in bytes */
bitmap_sz = BITS_TO_LONGS(tbl->it_size) * sizeof(unsigned long);
@@ -748,7 +748,21 @@ void iommu_free_table(struct iommu_table *tbl, const char *node_name)
/* free table */
kfree(tbl);
}
-EXPORT_SYMBOL_GPL(iommu_free_table);
+
+void iommu_table_get(struct iommu_table *tbl)
+{
+ kref_get(&tbl->it_kref);
+}
+EXPORT_SYMBOL_GPL(iommu_table_get);
+
+void iommu_table_put(struct iommu_table *tbl)
+{
+ if (!tbl)
+ return;
+
+ kref_put(&tbl->it_kref, iommu_table_free);
+}
+EXPORT_SYMBOL_GPL(iommu_table_put);

/* Creates TCEs for a user provided buffer. The user buffer must be
* contiguous real kernel storage (not vmalloc). The address passed here
diff --git a/arch/powerpc/platforms/powernv/pci-ioda.c b/arch/powerpc/platforms/powernv/pci-ioda.c
index cf0d8aed652a..f2c2ab8fbb3e 100644
--- a/arch/powerpc/platforms/powernv/pci-ioda.c
+++ b/arch/powerpc/platforms/powernv/pci-ioda.c
@@ -1422,7 +1422,7 @@ static void pnv_pci_ioda2_release_dma_pe(struct pci_dev *dev, struct pnv_ioda_pe
iommu_group_put(pe->table_group.group);
BUG_ON(pe->table_group.group);
}
- iommu_free_table(tbl, of_node_full_name(dev->dev.of_node));
+ iommu_table_put(tbl);
}

static void pnv_ioda_release_vf_PE(struct pci_dev *pdev)
@@ -2221,7 +2221,7 @@ static void pnv_pci_ioda1_setup_dma_pe(struct pnv_phb *phb,
__free_pages(tce_mem, get_order(tce32_segsz * segs));
if (tbl) {
pnv_pci_unlink_table_and_group(tbl, &pe->table_group);
- iommu_free_table(tbl, "pnv");
+ iommu_table_put(tbl);
}
}

@@ -2315,7 +2315,7 @@ static long pnv_pci_ioda2_create_table(struct iommu_table_group *table_group,
bus_offset, page_shift, window_size,
levels, tbl);
if (ret) {
- iommu_free_table(tbl, "pnv");
+ iommu_table_put(tbl);
return ret;
}

@@ -2361,7 +2361,7 @@ static long pnv_pci_ioda2_setup_default_config(struct pnv_ioda_pe *pe)
if (rc) {
pe_err(pe, "Failed to configure 32-bit TCE table, err %ld\n",
rc);
- iommu_free_table(tbl, "");
+ iommu_table_put(tbl);
return rc;
}

@@ -2447,7 +2447,7 @@ static void pnv_ioda2_take_ownership(struct iommu_table_group *table_group)

pnv_pci_ioda2_set_bypass(pe, false);
pnv_pci_ioda2_unset_window(&pe->table_group, 0);
- iommu_free_table(tbl, "pnv");
+ iommu_table_put(tbl);
}

static void pnv_ioda2_release_ownership(struct iommu_table_group *table_group)
@@ -3417,7 +3417,7 @@ static void pnv_pci_ioda1_release_pe_dma(struct pnv_ioda_pe *pe)
}

free_pages(tbl->it_base, get_order(tbl->it_size << 3));
- iommu_free_table(tbl, "pnv");
+ iommu_table_put(tbl);
}

static void pnv_pci_ioda2_release_pe_dma(struct pnv_ioda_pe *pe)
@@ -3444,7 +3444,7 @@ static void pnv_pci_ioda2_release_pe_dma(struct pnv_ioda_pe *pe)
}

pnv_pci_ioda2_table_free_pages(tbl);
- iommu_free_table(tbl, "pnv");
+ iommu_table_put(tbl);
}

static void pnv_ioda_free_pe_seg(struct pnv_ioda_pe *pe,
diff --git a/arch/powerpc/platforms/powernv/pci.c b/arch/powerpc/platforms/powernv/pci.c
index c6d554fe585c..471210913e42 100644
--- a/arch/powerpc/platforms/powernv/pci.c
+++ b/arch/powerpc/platforms/powernv/pci.c
@@ -767,6 +767,7 @@ struct iommu_table *pnv_pci_table_alloc(int nid)

tbl = kzalloc_node(sizeof(struct iommu_table), GFP_KERNEL, nid);
INIT_LIST_HEAD_RCU(&tbl->it_group_list);
+ kref_init(&tbl->it_kref);

return tbl;
}
diff --git a/arch/powerpc/platforms/pseries/iommu.c b/arch/powerpc/platforms/pseries/iommu.c
index dc2577fc5fbb..47f0501a94f9 100644
--- a/arch/powerpc/platforms/pseries/iommu.c
+++ b/arch/powerpc/platforms/pseries/iommu.c
@@ -74,6 +74,7 @@ static struct iommu_table_group *iommu_pseries_alloc_group(int node)
goto fail_exit;

INIT_LIST_HEAD_RCU(&tbl->it_group_list);
+ kref_init(&tbl->it_kref);
tgl->table_group = table_group;
list_add_rcu(&tgl->next, &tbl->it_group_list);

@@ -115,7 +116,7 @@ static void iommu_pseries_free_group(struct iommu_table_group *table_group,
BUG_ON(table_group->group);
}
#endif
- iommu_free_table(tbl, node_name);
+ iommu_table_put(tbl);

kfree(table_group);
}
diff --git a/arch/powerpc/platforms/pseries/vio.c b/arch/powerpc/platforms/pseries/vio.c
index 2c8fb3ec989e..41e8aa5c0d6a 100644
--- a/arch/powerpc/platforms/pseries/vio.c
+++ b/arch/powerpc/platforms/pseries/vio.c
@@ -1318,7 +1318,7 @@ static void vio_dev_release(struct device *dev)
struct iommu_table *tbl = get_iommu_table_base(dev);

if (tbl)
- iommu_free_table(tbl, of_node_full_name(dev->of_node));
+ iommu_table_put(tbl);
of_node_put(dev->of_node);
kfree(to_vio_dev(dev));
}
diff --git a/drivers/vfio/vfio_iommu_spapr_tce.c b/drivers/vfio/vfio_iommu_spapr_tce.c
index 6e79be9dfb43..b29ccb54aa7a 100644
--- a/drivers/vfio/vfio_iommu_spapr_tce.c
+++ b/drivers/vfio/vfio_iommu_spapr_tce.c
@@ -677,7 +677,7 @@ static void tce_iommu_free_table(struct tce_container *container,
unsigned long pages = tbl->it_allocated_size >> PAGE_SHIFT;

tce_iommu_userspace_view_free(tbl, container->mm);
- iommu_free_table(tbl, "");
+ iommu_table_put(tbl);
decrement_locked_vm(container->mm, pages);
}

--
2.11.0