[PATCH kernel v9 13/32] vfio: powerpc/spapr/iommu/powernv/ioda2: Rework IOMMU ownership control

Alexey Kardashevskiy
2015-04-25T12:19:55Z

This adds tce_iommu_take_ownership() and tce_iommu_release_ownership
which call in a loop iommu_take_ownership()/iommu_release_ownership()
for every table on the group. As there is just one now, no change in
behaviour is expected.

At the moment the iommu_table struct has a set_bypass() which enables/
disables DMA bypass on IODA2 PHB. This is exposed to POWERPC IOMMU code
which calls this callback when external IOMMU users such as VFIO are
about to get over a PHB.

The set_bypass() callback is not really an iommu_table function but
IOMMU/PE function. This introduces a iommu_table_group_ops struct and
adds take_ownership()/release_ownership() callbacks to it which are
called when an external user takes/releases control over the IOMMU.

This replaces set_bypass() with ownership callbacks as it is not
necessarily just bypass enabling, it can be something else/more
so let's give it more generic name.

The callbacks is implemented for IODA2 only. Other platforms (P5IOC2,
IODA1) will use the old iommu_take_ownership/iommu_release_ownership API.
The following patches will replace iommu_take_ownership/
iommu_release_ownership calls in IODA2 with full IOMMU table release/
create.

Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
[aw: for the vfio related changes]
Acked-by: Alex Williamson <alex.williamson@redhat.com>
---
Changes:
v9:
* squashed "vfio: powerpc/spapr: powerpc/iommu: Rework IOMMU ownership control"
and "vfio: powerpc/spapr: powerpc/powernv/ioda2: Rework IOMMU ownership control"
into a single patch
* moved helpers with a loop through tables in a group
to vfio_iommu_spapr_tce.c to keep the platform code free of IOMMU table
groups as much as possible
* added missing tce_iommu_clear() to tce_iommu_release_ownership()
* replaced the set_ownership(enable) callback with take_ownership() and
release_ownership()
---
arch/powerpc/include/asm/iommu.h | 13 +++++-
arch/powerpc/kernel/iommu.c | 11 ------
arch/powerpc/platforms/powernv/pci-ioda.c | 40 +++++++++++++++----
drivers/vfio/vfio_iommu_spapr_tce.c | 66 +++++++++++++++++++++++++++----
4 files changed, 103 insertions(+), 27 deletions(-)

diff --git a/arch/powerpc/include/asm/iommu.h b/arch/powerpc/include/asm/iommu.h
index fa37519..e63419e 100644
--- a/arch/powerpc/include/asm/iommu.h
+++ b/arch/powerpc/include/asm/iommu.h
@@ -93,7 +93,6 @@ struct iommu_table {
unsigned long it_page_shift;/* table iommu page size */
struct iommu_table_group *it_table_group;
struct iommu_table_ops *it_ops;
- void (*set_bypass)(struct iommu_table *tbl, bool enable);
};

/* Pure 2^n version of get_order */
@@ -128,11 +127,23 @@ extern struct iommu_table *iommu_init_table(struct iommu_table * tbl,

#define IOMMU_TABLE_GROUP_MAX_TABLES 1

+struct iommu_table_group;
+
+struct iommu_table_group_ops {
+ /*
+ * Switches ownership from the kernel itself to an external
+ * user. While onwership is taken, the kernel cannot use IOMMU itself.
+ */
+ void (*take_ownership)(struct iommu_table_group *table_group);
+ void (*release_ownership)(struct iommu_table_group *table_group);
+};
+
struct iommu_table_group {
#ifdef CONFIG_IOMMU_API
struct iommu_group *group;
#endif
struct iommu_table tables[IOMMU_TABLE_GROUP_MAX_TABLES];
+ struct iommu_table_group_ops *ops;
};

#ifdef CONFIG_IOMMU_API
diff --git a/arch/powerpc/kernel/iommu.c b/arch/powerpc/kernel/iommu.c
index 005146b..2856d27 100644
--- a/arch/powerpc/kernel/iommu.c
+++ b/arch/powerpc/kernel/iommu.c
@@ -1057,13 +1057,6 @@ int iommu_take_ownership(struct iommu_table *tbl)

memset(tbl->it_map, 0xff, sz);

- /*
- * Disable iommu bypass, otherwise the user can DMA to all of
- * our physical memory via the bypass window instead of just
- * the pages that has been explicitly mapped into the iommu
- */
- if (tbl->set_bypass)
- tbl->set_bypass(tbl, false);

return 0;
}
@@ -1078,10 +1071,6 @@ void iommu_release_ownership(struct iommu_table *tbl)
/* Restore bit#0 set by iommu_init_table() */
if (tbl->it_offset == 0)
set_bit(0, tbl->it_map);
-
- /* The kernel owns the device now, we can restore the iommu bypass */
- if (tbl->set_bypass)
- tbl->set_bypass(tbl, true);
}
EXPORT_SYMBOL_GPL(iommu_release_ownership);

diff --git a/arch/powerpc/platforms/powernv/pci-ioda.c b/arch/powerpc/platforms/powernv/pci-ioda.c
index 88472cb..718d5cc 100644
--- a/arch/powerpc/platforms/powernv/pci-ioda.c
+++ b/arch/powerpc/platforms/powernv/pci-ioda.c
@@ -1870,10 +1870,8 @@ static void pnv_pci_ioda_setup_dma_pe(struct pnv_phb *phb,
__free_pages(tce_mem, get_order(TCE32_TABLE_SIZE * segs));
}

-static void pnv_pci_ioda2_set_bypass(struct iommu_table *tbl, bool enable)
+static void pnv_pci_ioda2_set_bypass(struct pnv_ioda_pe *pe, bool enable)
{
- struct pnv_ioda_pe *pe = container_of(tbl->it_table_group,
- struct pnv_ioda_pe, table_group);
uint16_t window_id = (pe->pe_number << 1 ) + 1;
int64_t rc;

@@ -1901,7 +1899,8 @@ static void pnv_pci_ioda2_set_bypass(struct iommu_table *tbl, bool enable)
* host side.
*/
if (pe->pdev)
- set_iommu_table_base(&pe->pdev->dev, tbl);
+ set_iommu_table_base(&pe->pdev->dev,
+ &pe->table_group.tables[0]);
else
pnv_ioda_setup_bus_dma(pe, pe->pbus, false);
}
@@ -1917,13 +1916,35 @@ static void pnv_pci_ioda2_setup_bypass_pe(struct pnv_phb *phb,
/* TVE #1 is selected by PCI address bit 59 */
pe->tce_bypass_base = 1ull << 59;

- /* Install set_bypass callback for VFIO */
- pe->table_group.tables[0].set_bypass = pnv_pci_ioda2_set_bypass;
-
/* Enable bypass by default */
- pnv_pci_ioda2_set_bypass(&pe->table_group.tables[0], true);
+ pnv_pci_ioda2_set_bypass(pe, true);
}

+#ifdef CONFIG_IOMMU_API
+static void pnv_ioda2_take_ownership(struct iommu_table_group *table_group)
+{
+ struct pnv_ioda_pe *pe = container_of(table_group, struct pnv_ioda_pe,
+ table_group);
+
+ iommu_take_ownership(&table_group->tables[0]);
+ pnv_pci_ioda2_set_bypass(pe, false);
+}
+
+static void pnv_ioda2_release_ownership(struct iommu_table_group *table_group)
+{
+ struct pnv_ioda_pe *pe = container_of(table_group, struct pnv_ioda_pe,
+ table_group);
+
+ iommu_release_ownership(&table_group->tables[0]);
+ pnv_pci_ioda2_set_bypass(pe, true);
+}
+
+static struct iommu_table_group_ops pnv_pci_ioda2_ops = {
+ .take_ownership = pnv_ioda2_take_ownership,
+ .release_ownership = pnv_ioda2_release_ownership,
+};
+#endif
+
static void pnv_pci_ioda2_setup_dma_pe(struct pnv_phb *phb,
struct pnv_ioda_pe *pe)
{
@@ -1991,6 +2012,9 @@ static void pnv_pci_ioda2_setup_dma_pe(struct pnv_phb *phb,
}
tbl->it_ops = &pnv_ioda2_iommu_ops;
iommu_init_table(tbl, phb->hose->node);
+#ifdef CONFIG_IOMMU_API
+ pe->table_group.ops = &pnv_pci_ioda2_ops;
+#endif

if (pe->flags & PNV_IODA_PE_DEV) {
iommu_register_group(&pe->table_group, phb->hose->global_number,
diff --git a/drivers/vfio/vfio_iommu_spapr_tce.c b/drivers/vfio/vfio_iommu_spapr_tce.c
index 17e884a..dacc738 100644
--- a/drivers/vfio/vfio_iommu_spapr_tce.c
+++ b/drivers/vfio/vfio_iommu_spapr_tce.c
@@ -483,6 +483,43 @@ static long tce_iommu_ioctl(void *iommu_data,
return -ENOTTY;
}

+static void tce_iommu_release_ownership(struct tce_container *container,
+ struct iommu_table_group *table_group)
+{
+ int i;
+
+ for (i = 0; i < IOMMU_TABLE_GROUP_MAX_TABLES; ++i) {
+ struct iommu_table *tbl = &table_group->tables[i];
+
+ tce_iommu_clear(container, tbl, tbl->it_offset, tbl->it_size);
+ if (tbl->it_map)
+ iommu_release_ownership(tbl);
+ }
+}
+
+static int tce_iommu_take_ownership(struct iommu_table_group *table_group)
+{
+ int i, j, rc = 0;
+
+ for (i = 0; i < IOMMU_TABLE_GROUP_MAX_TABLES; ++i) {
+ struct iommu_table *tbl = &table_group->tables[i];
+
+ if (!tbl->it_map)
+ continue;
+
+ rc = iommu_take_ownership(tbl);
+ if (rc) {
+ for (j = 0; j < i; ++j)
+ iommu_release_ownership(
+ &table_group->tables[j]);
+
+ return rc;
+ }
+ }
+
+ return 0;
+}
+
static int tce_iommu_attach_group(void *iommu_data,
struct iommu_group *iommu_group)
{
@@ -515,9 +552,23 @@ static int tce_iommu_attach_group(void *iommu_data,
goto unlock_exit;
}

- ret = iommu_take_ownership(&table_group->tables[0]);
- if (!ret)
- container->grp = iommu_group;
+ if (!table_group->ops || !table_group->ops->take_ownership ||
+ !table_group->ops->release_ownership) {
+ ret = tce_iommu_take_ownership(table_group);
+ } else {
+ /*
+ * Disable iommu bypass, otherwise the user can DMA to all of
+ * our physical memory via the bypass window instead of just
+ * the pages that has been explicitly mapped into the iommu
+ */
+ table_group->ops->take_ownership(table_group);
+ ret = 0;
+ }
+
+ if (ret)
+ goto unlock_exit;
+
+ container->grp = iommu_group;

unlock_exit:
mutex_unlock(&container->lock);
@@ -530,7 +581,6 @@ static void tce_iommu_detach_group(void *iommu_data,
{
struct tce_container *container = iommu_data;
struct iommu_table_group *table_group;
- struct iommu_table *tbl;

mutex_lock(&container->lock);
if (iommu_group != container->grp) {
@@ -553,9 +603,11 @@ static void tce_iommu_detach_group(void *iommu_data,
table_group = iommu_group_get_iommudata(iommu_group);
BUG_ON(!table_group);

- tbl = &table_group->tables[0];
- tce_iommu_clear(container, tbl, tbl->it_offset, tbl->it_size);
- iommu_release_ownership(tbl);
+ /* Kernel owns the device now, we can restore bypass */
+ if (!table_group->ops || !table_group->ops->release_ownership)
+ tce_iommu_release_ownership(container, table_group);
+ else
+ table_group->ops->release_ownership(table_group);

unlock_exit:
mutex_unlock(&container->lock);
--
2.0.0