[PATCH] vfio powerpc: enabled on powernv platform

[Alexey Kardashevskiy]

This patch initializes IOMMU groups based on the IOMMU
configuration discovered during the PCI scan on POWERNV
(POWER non virtualized) platform. The IOMMU groups are
to be used later by VFIO driver (PCI pass through).

It also implements an API for mapping/unmapping pages for
guest PCI drivers and providing DMA window properties.
This API is going to be used later by QEMU-VFIO to handle
h_put_tce hypercalls from the KVM guest.

Although this driver has been tested only on the POWERNV
platform, it should work on any platform which supports
TCE tables.

To enable VFIO on POWER, enable SPAPR_TCE_IOMMU config
option and configure VFIO as required.

Cc: David Gibson <david@xxxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Alexey Kardashevskiy <aik@xxxxxxxxx>
---
 arch/powerpc/include/asm/iommu.h     |   10 ++
 arch/powerpc/kernel/iommu.c          |  214 ++++++++++++++++++++++++++++++++++
 arch/powerpc/platforms/powernv/pci.c |  134 +++++++++++++++++++++
 drivers/iommu/Kconfig                |    8 ++
 4 files changed, 366 insertions(+)

diff --git a/arch/powerpc/include/asm/iommu.h b/arch/powerpc/include/asm/iommu.h
index cbfe678..be3b11b 100644
--- a/arch/powerpc/include/asm/iommu.h
+++ b/arch/powerpc/include/asm/iommu.h
@@ -76,6 +76,9 @@ struct iommu_table {
 	struct iommu_pool large_pool;
 	struct iommu_pool pools[IOMMU_NR_POOLS];
 	unsigned long *it_map;       /* A simple allocation bitmap for now */
+#ifdef CONFIG_IOMMU_API
+	struct iommu_group *it_group;
+#endif
 };
 
 struct scatterlist;
@@ -147,5 +150,12 @@ static inline void iommu_restore(void)
 }
 #endif
 
+extern void iommu_reset_table(struct iommu_table *tbl, bool release);
+extern long iommu_clear_tces(struct iommu_table *tbl, unsigned long entry,
+		unsigned long pages);
+extern long iommu_put_tces(struct iommu_table *tbl, unsigned long entry,
+		uint64_t tce, enum dma_data_direction direction,
+		unsigned long pages);
+
 #endif /* __KERNEL__ */
 #endif /* _ASM_IOMMU_H */
diff --git a/arch/powerpc/kernel/iommu.c b/arch/powerpc/kernel/iommu.c
index ff5a6ce..123431a 100644
--- a/arch/powerpc/kernel/iommu.c
+++ b/arch/powerpc/kernel/iommu.c
@@ -44,6 +44,7 @@
 #include <asm/kdump.h>
 #include <asm/fadump.h>
 #include <asm/vio.h>
+#include <asm/tce.h>
 
 #define DBG(...)
 
@@ -856,3 +857,216 @@ void iommu_free_coherent(struct iommu_table *tbl, size_t size,
 		free_pages((unsigned long)vaddr, get_order(size));
 	}
 }
+
+#ifdef CONFIG_IOMMU_API
+/*
+ * SPAPR TCE API
+ */
+
+/*
+ * iommu_reset_table is called when it started/stopped being used
+ */
+void iommu_reset_table(struct iommu_table *tbl, bool release)
+{
+	/*
+	 * Page at 0 is marked as used in iommu_init_table,
+	 * so here we clear it when called with release=false...
+	 */
+	if (!release && (tbl->it_offset == 0))
+		clear_bit(0, tbl->it_map);
+
+	iommu_clear_tces(tbl, tbl->it_offset, tbl->it_size);
+
+	memset(tbl->it_map, 0, (tbl->it_size + 7) >> 3);
+
+	/*
+	 * ... or restore when release=true
+	 */
+	if (release && (tbl->it_offset == 0))
+		set_bit(0, tbl->it_map);
+}
+EXPORT_SYMBOL_GPL(iommu_reset_table);
+
+/*
+ * Returns the number of used IOMMU pages (4K) within
+ * the same system page (4K or 64K).
+ * bitmap_weight is not used as it does not support bigendian maps.
+ * "offset" is an IOMMU page number relative to DMA window start.
+ */
+static int syspage_weight(unsigned long *map, unsigned long offset)
+{
+	int ret = 0, nbits = PAGE_SIZE/IOMMU_PAGE_SIZE;
+
+	/* Aligns TCE entry number to system page boundary */
+	offset &= PAGE_MASK >> IOMMU_PAGE_SHIFT;
+
+	/* Count used 4K pages */
+	while (nbits) {
+		if (test_bit(offset, map))
+			++ret;
+		--nbits;
+		++offset;
+	}
+
+	return ret;
+}
+
+static void tce_flush(struct iommu_table *tbl)
+{
+	/* Flush/invalidate TLB caches if necessary */
+	if (ppc_md.tce_flush)
+		ppc_md.tce_flush(tbl);
+
+	/* Make sure updates are seen by hardware */
+	mb();
+}
+
+/*
+ * iommu_clear_tces clears tces and returned the number of system pages
+ * which it called put_page() on
+ */
+static long clear_tces_nolock(struct iommu_table *tbl, unsigned long entry,
+		unsigned long pages)
+{
+	int i, retpages = 0, clr;
+	unsigned long oldtce, oldweight;
+	struct page *page;
+
+	for (i = 0; i < pages; ++i) {
+		if (!test_bit(entry + i - tbl->it_offset, tbl->it_map))
+			continue;
+
+		oldtce = ppc_md.tce_get(tbl, entry + i);
+		ppc_md.tce_free(tbl, entry + i, 1);
+
+		oldweight = syspage_weight(tbl->it_map,
+				entry + i - tbl->it_offset);
+		clr = __test_and_clear_bit(entry + i - tbl->it_offset,
+				tbl->it_map);
+
+		if (WARN_ON(!(oldtce & (TCE_PCI_WRITE | TCE_PCI_READ))))
+			continue;
+
+		page = pfn_to_page(oldtce >> PAGE_SHIFT);
+
+		if (WARN_ON(!page))
+			continue;
+
+		if (oldtce & TCE_PCI_WRITE)
+			SetPageDirty(page);
+
+		put_page(page);
+
+		/* That was the last IOMMU page within the system page */
+		if ((oldweight == 1) && clr)
+			++retpages;
+	}
+
+	return retpages;
+}
+
+/*
+ * iommu_clear_tces clears tces and returned the number
+ * of released system pages
+ */
+long iommu_clear_tces(struct iommu_table *tbl, unsigned long entry,
+		unsigned long pages)
+{
+	int ret;
+	struct iommu_pool *pool = get_pool(tbl, entry);
+
+	spin_lock(&(pool->lock));
+	ret = clear_tces_nolock(tbl, entry, pages);
+	tce_flush(tbl);
+	spin_unlock(&(pool->lock));
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(iommu_clear_tces);
+
+static int put_tce(struct iommu_table *tbl, unsigned long entry,
+		uint64_t tce, enum dma_data_direction direction)
+{
+	int ret;
+	struct page *page = NULL;
+	unsigned long kva, offset, oldweight;
+
+	/* Map new TCE */
+	offset = (tce & IOMMU_PAGE_MASK) - (tce & PAGE_MASK);
+	ret = get_user_pages_fast(tce & PAGE_MASK, 1,
+			direction != DMA_TO_DEVICE, &page);
+	if (ret != 1) {
+		pr_err("tce_vfio: get_user_pages_fast failed tce=%llx ioba=%lx ret=%d\n",
+				tce, entry << IOMMU_PAGE_SHIFT, ret);
+		return -EFAULT;
+	}
+
+	kva = (unsigned long) page_address(page);
+	kva += offset;
+
+	/* tce_build receives a virtual address */
+	ret = ppc_md.tce_build(tbl, entry, 1, kva, direction, NULL);
+
+	/* tce_build() only returns non-zero for transient errors */
+	if (unlikely(ret)) {
+		pr_err("tce_vfio: tce_put failed on tce=%llx ioba=%lx kva=%lx ret=%d\n",
+				tce, entry << IOMMU_PAGE_SHIFT, kva, ret);
+		put_page(page);
+		return -EIO;
+	}
+
+	/* Calculate if new system page has been locked */
+	oldweight = syspage_weight(tbl->it_map, entry - tbl->it_offset);
+	__set_bit(entry - tbl->it_offset, tbl->it_map);
+
+	return (oldweight == 0) ? 1 : 0;
+}
+
+/*
+ * iommu_put_tces builds tces and returned the number of actually
+ * locked system pages
+ */
+long iommu_put_tces(struct iommu_table *tbl, unsigned long entry,
+		uint64_t tce, enum dma_data_direction direction,
+		unsigned long pages)
+{
+	int i, ret = 0, retpages = 0;
+	struct iommu_pool *pool = get_pool(tbl, entry);
+
+	BUILD_BUG_ON(PAGE_SIZE < IOMMU_PAGE_SIZE);
+	BUG_ON(direction == DMA_NONE);
+
+	spin_lock(&(pool->lock));
+
+	/* Check if any is in use */
+	for (i = 0; i < pages; ++i) {
+		if (test_bit(entry + i - tbl->it_offset, tbl->it_map)) {
+			spin_unlock(&(pool->lock));
+			return -EBUSY;
+		}
+	}
+
+	/* Put tces to the table */
+	for (i = 0; (i < pages) && (ret >= 0); ++i, tce += IOMMU_PAGE_SIZE) {
+		ret = put_tce(tbl, entry + i, tce, direction);
+		if (ret == 1)
+			++retpages;
+	}
+
+	/*
+	 * If failed, release locked pages, otherwise return the number
+	 * of locked system pages
+	 */
+	if (ret < 0)
+		clear_tces_nolock(tbl, entry, i);
+	else
+		ret = retpages;
+
+	tce_flush(tbl);
+	spin_unlock(&(pool->lock));
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(iommu_put_tces);
+
+#endif /* CONFIG_IOMMU_API */
diff --git a/arch/powerpc/platforms/powernv/pci.c b/arch/powerpc/platforms/powernv/pci.c
index 05205cf..1b970bf 100644
--- a/arch/powerpc/platforms/powernv/pci.c
+++ b/arch/powerpc/platforms/powernv/pci.c
@@ -20,6 +20,7 @@
 #include <linux/irq.h>
 #include <linux/io.h>
 #include <linux/msi.h>
+#include <linux/iommu.h>
 
 #include <asm/sections.h>
 #include <asm/io.h>
@@ -613,3 +614,136 @@ void __init pnv_pci_init(void)
 	ppc_md.teardown_msi_irqs = pnv_teardown_msi_irqs;
 #endif
 }
+
+#ifdef CONFIG_IOMMU_API
+/*
+ * IOMMU groups support required by VFIO
+ */
+static int add_device(struct device *dev)
+{
+	struct iommu_table *tbl;
+	int ret = 0;
+
+	if (WARN_ON(dev->iommu_group)) {
+		pr_warn("tce_vfio: device %s is already in iommu group %d, skipping\n",
+				dev_name(dev),
+				iommu_group_id(dev->iommu_group));
+		return -EBUSY;
+	}
+
+	tbl = get_iommu_table_base(dev);
+	if (!tbl) {
+		pr_debug("tce_vfio: skipping device %s with no tbl\n",
+				dev_name(dev));
+		return 0;
+	}
+
+	pr_debug("tce_vfio: adding %s to iommu group %d\n",
+			dev_name(dev), iommu_group_id(tbl->it_group));
+
+	ret = iommu_group_add_device(tbl->it_group, dev);
+	if (ret < 0)
+		pr_err("tce_vfio: %s has not been added, ret=%d\n",
+				dev_name(dev), ret);
+
+	return ret;
+}
+
+static void del_device(struct device *dev)
+{
+	iommu_group_remove_device(dev);
+}
+
+static int iommu_bus_notifier(struct notifier_block *nb,
+			      unsigned long action, void *data)
+{
+	struct device *dev = data;
+
+	switch (action) {
+	case BUS_NOTIFY_ADD_DEVICE:
+		return add_device(dev);
+	case BUS_NOTIFY_DEL_DEVICE:
+		del_device(dev);
+		return 0;
+	default:
+		return 0;
+	}
+}
+
+static struct notifier_block tce_iommu_bus_nb = {
+	.notifier_call = iommu_bus_notifier,
+};
+
+static void group_release(void *iommu_data)
+{
+	struct iommu_table *tbl = iommu_data;
+	tbl->it_group = NULL;
+}
+
+static int __init tce_iommu_init(void)
+{
+	struct pci_dev *pdev = NULL;
+	struct iommu_table *tbl;
+	struct iommu_group *grp;
+
+	/* Allocate and initialize IOMMU groups */
+	for_each_pci_dev(pdev) {
+		tbl = get_iommu_table_base(&pdev->dev);
+		if (!tbl)
+			continue;
+
+		/* Skip already initialized */
+		if (tbl->it_group)
+			continue;
+
+		grp = iommu_group_alloc();
+		if (IS_ERR(grp)) {
+			pr_info("tce_vfio: cannot create new IOMMU group, ret=%ld\n",
+					PTR_ERR(grp));
+			return PTR_ERR(grp);
+		}
+		tbl->it_group = grp;
+		iommu_group_set_iommudata(grp, tbl, group_release);
+	}
+
+	bus_register_notifier(&pci_bus_type, &tce_iommu_bus_nb);
+
+	/* Add PCI devices to VFIO groups */
+	for_each_pci_dev(pdev)
+		add_device(&pdev->dev);
+
+	return 0;
+}
+
+static void __exit tce_iommu_cleanup(void)
+{
+	struct pci_dev *pdev = NULL;
+	struct iommu_table *tbl;
+	struct iommu_group *grp = NULL;
+
+	bus_unregister_notifier(&pci_bus_type, &tce_iommu_bus_nb);
+
+	/* Delete PCI devices from VFIO groups */
+	for_each_pci_dev(pdev)
+		del_device(&pdev->dev);
+
+	/* Release VFIO groups */
+	for_each_pci_dev(pdev) {
+		tbl = get_iommu_table_base(&pdev->dev);
+		if (!tbl)
+			continue;
+		grp = tbl->it_group;
+
+		/* Skip (already) uninitialized */
+		if (!grp)
+			continue;
+
+		/* Do actual release, group_release() is expected to work */
+		iommu_group_put(grp);
+		BUG_ON(tbl->it_group);
+	}
+}
+
+module_init(tce_iommu_init);
+module_exit(tce_iommu_cleanup);
+#endif /* CONFIG_IOMMU_API */
diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
index 9f69b56..29d11dc 100644
--- a/drivers/iommu/Kconfig
+++ b/drivers/iommu/Kconfig
@@ -187,4 +187,12 @@ config EXYNOS_IOMMU_DEBUG
 
 	  Say N unless you need kernel log message for IOMMU debugging
 
+config SPAPR_TCE_IOMMU
+	bool "sPAPR TCE IOMMU Support"
+	depends on PPC_POWERNV
+	select IOMMU_API
+	help
+	  Enables bits of IOMMU API required by VFIO. The iommu_ops is
+	  still not implemented.
+
 endif # IOMMU_SUPPORT
-- 
1.7.10.4

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