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SubjectRe: [PATCH] vfio powerpc: enabled on powernv platform
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On Fri, 2012-12-07 at 18:35 +1100, Alexey Kardashevskiy wrote:
> 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@gibson.dropbear.id.au>
> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
> ---
> 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);

Isn't this redundant to the memset below?

> +
> + 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);

"release" to me implies something is freed, maybe this should just be
called "restore".

> +}
> +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) {

Any reason not to increment "entry" and avoid the 5 cases of "entry + i"
below?

> + 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;

It seems like there's an optimization for syspage_weight since you only
care about two cases, ie. syspage_weight_one and syspage_weight_zero.
The zero test is easy, just mask and return !! the value. Testing
weight 1 means you don't have to find more than 2 bits set. I won't
hold you to that optimization, just fyi.

> +}
> +
> +/*
> + * 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)) {

Again, seems like there's an optimization here that avoids individually
testing bits since you only care about zero or non-zero for a sequential
run.

> + 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);

BTW, groups have a name property that shows up in sysfs that can be set
with iommu_group_set_name(). IIRC, this was a feature David requested
for PEs. It'd be nice if it was used for PEs... Thanks,

Alex

> + }
> +
> + 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





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