[PATCH kernel v10 18/34] vfio: powerpc/spapr/iommu/powernv/ioda2: Rework IOMMU ownership control

[Alexey Kardashevskiy]

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.

As we here and touching bypass control, this removes
pnv_pci_ioda2_setup_bypass_pe() as it does not do much
more compared to pnv_pci_ioda2_set_bypass. This moves tce_bypass_base
initialization to pnv_pci_ioda2_setup_dma_pe.

Signed-off-by: Alexey Kardashevskiy <aik@xxxxxxxxx>
[aw: for the vfio related changes]
Acked-by: Alex Williamson <alex.williamson@xxxxxxxxxx>
---
Changes:
v10:
* fixed comments around take_ownership/release_ownership in iommu_table_group_ops

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          | 11 ++++-
 arch/powerpc/kernel/iommu.c               | 12 -----
 arch/powerpc/platforms/powernv/pci-ioda.c | 73 ++++++++++++++++++-------------
 drivers/vfio/vfio_iommu_spapr_tce.c       | 70 ++++++++++++++++++++++++++---
 4 files changed, 116 insertions(+), 50 deletions(-)

diff --git a/arch/powerpc/include/asm/iommu.h b/arch/powerpc/include/asm/iommu.h
index 664beeb..c5375c5 100644
--- a/arch/powerpc/include/asm/iommu.h
+++ b/arch/powerpc/include/asm/iommu.h
@@ -95,7 +95,6 @@ struct iommu_table {
 	struct list_head it_group_list;/* List of iommu_table_group_link */
 #endif
 	struct iommu_table_ops *it_ops;
-	void (*set_bypass)(struct iommu_table *tbl, bool enable);
 };
 
 /* Pure 2^n version of get_order */
@@ -130,6 +129,15 @@ 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 {
+	/* Switch ownership from platform code to external user (e.g. VFIO) */
+	void (*take_ownership)(struct iommu_table_group *table_group);
+	/* Switch ownership from external user (e.g. VFIO) back to core */
+	void (*release_ownership)(struct iommu_table_group *table_group);
+};
+
 struct iommu_table_group_link {
 	struct list_head next;
 	struct rcu_head rcu;
@@ -139,6 +147,7 @@ struct iommu_table_group_link {
 struct iommu_table_group {
 	struct iommu_group *group;
 	struct iommu_table *tables[IOMMU_TABLE_GROUP_MAX_TABLES];
+	struct iommu_table_group_ops *ops;
 };
 
 extern void iommu_register_group(struct iommu_table_group *table_group,
diff --git a/arch/powerpc/kernel/iommu.c b/arch/powerpc/kernel/iommu.c
index bdf19c6..7e54714 100644
--- a/arch/powerpc/kernel/iommu.c
+++ b/arch/powerpc/kernel/iommu.c
@@ -1044,14 +1044,6 @@ 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;
 }
 EXPORT_SYMBOL_GPL(iommu_take_ownership);
@@ -1065,10 +1057,6 @@ 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 53bf242b..35ab19c8 100644
--- a/arch/powerpc/platforms/powernv/pci-ioda.c
+++ b/arch/powerpc/platforms/powernv/pci-ioda.c
@@ -1918,13 +1918,8 @@ static void pnv_pci_ioda_setup_dma_pe(struct pnv_phb *phb,
 	}
 }
 
-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 iommu_table_group_link *tgl = list_first_entry_or_null(
-			&tbl->it_group_list, struct iommu_table_group_link,
-			next);
-	struct pnv_ioda_pe *pe = container_of(tgl->table_group,
-			struct pnv_ioda_pe, table_group);
 	uint16_t window_id = (pe->pe_number << 1 ) + 1;
 	int64_t rc;
 
@@ -1951,33 +1946,48 @@ static void pnv_pci_ioda2_set_bypass(struct iommu_table *tbl, bool enable)
 		pe->tce_bypass_enabled = enable;
 }
 
-static void pnv_pci_ioda2_setup_bypass_pe(struct pnv_phb *phb,
-					  struct pnv_ioda_pe *pe)
+#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)
+{
+	struct page *tce_mem = NULL;
+	void *addr;
+	const __be64 *swinvp;
+	struct iommu_table *tbl;
+	unsigned int tce_table_size, end;
+	int64_t rc;
+
+	/* We shouldn't already have a 32-bit DMA associated */
+	if (WARN_ON(pe->tce32_seg >= 0))
+		return;
+
 	/* 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);
-}
-
-static void pnv_pci_ioda2_setup_dma_pe(struct pnv_phb *phb,
-				       struct pnv_ioda_pe *pe)
-{
-	struct page *tce_mem = NULL;
-	void *addr;
-	const __be64 *swinvp;
-	struct iommu_table *tbl;
-	unsigned int tce_table_size, end;
-	int64_t rc;
-
-	/* We shouldn't already have a 32-bit DMA associated */
-	if (WARN_ON(pe->tce32_seg >= 0))
-		return;
-
 	tbl = pnv_pci_table_alloc(phb->hose->node);
 	iommu_register_group(&pe->table_group, phb->hose->global_number,
 			pe->pe_number);
@@ -2032,6 +2042,9 @@ 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) {
 		/*
@@ -2046,7 +2059,7 @@ static void pnv_pci_ioda2_setup_dma_pe(struct pnv_phb *phb,
 
 	/* Also create a bypass window */
 	if (!pnv_iommu_bypass_disabled)
-		pnv_pci_ioda2_setup_bypass_pe(phb, pe);
+		pnv_pci_ioda2_set_bypass(pe, true);
 
 	return;
 fail:
diff --git a/drivers/vfio/vfio_iommu_spapr_tce.c b/drivers/vfio/vfio_iommu_spapr_tce.c
index ed3310b..2ead291 100644
--- a/drivers/vfio/vfio_iommu_spapr_tce.c
+++ b/drivers/vfio/vfio_iommu_spapr_tce.c
@@ -486,6 +486,47 @@ 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];
+
+		if (!tbl)
+			continue;
+
+		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 tce_container *container,
+		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 || !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)
 {
@@ -518,9 +559,23 @@ 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(container, 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);
@@ -533,7 +588,6 @@ 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) {
@@ -556,9 +610,11 @@ 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);
-- 
2.4.0.rc3.8.gfb3e7d5

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