Re: [PATCH kernel v9 22/32] powerpc/powernv: Implement multilevel TCE tables

David Gibson
2015-04-29T05:52:00Z

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On Sat, Apr 25, 2015 at 10:14:46PM +1000, Alexey Kardashevskiy wrote:
> TCE tables might get too big in case of 4K IOMMU pages and DDW enabled
> on huge guests (hundreds of GB of RAM) so the kernel might be unable to
> allocate contiguous chunk of physical memory to store the TCE table.
>
> To address this, POWER8 CPU (actually, IODA2) supports multi-level TCE tables,
> up to 5 levels which splits the table into a tree of smaller subtables.
>
> This adds multi-level TCE tables support to pnv_pci_create_table()
> and pnv_pci_free_table() helpers.
>
> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
> ---
> Changes:
> v9:
> * moved from ioda2 to common powernv pci code
> * fixed cleanup if allocation fails in a middle
> * removed check for the size - all boundary checks happen in the calling code
> anyway
> ---
> arch/powerpc/include/asm/iommu.h | 2 +
> arch/powerpc/platforms/powernv/pci-ioda.c | 15 +++--
> arch/powerpc/platforms/powernv/pci.c | 94 +++++++++++++++++++++++++++++--
> arch/powerpc/platforms/powernv/pci.h | 4 +-
> 4 files changed, 104 insertions(+), 11 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/iommu.h b/arch/powerpc/include/asm/iommu.h
> index 7e7ca0a..0f50ee2 100644
> --- a/arch/powerpc/include/asm/iommu.h
> +++ b/arch/powerpc/include/asm/iommu.h
> @@ -96,6 +96,8 @@ struct iommu_pool {
> struct iommu_table {
> unsigned long it_busno; /* Bus number this table belongs to */
> unsigned long it_size; /* Size of iommu table in entries */
> + unsigned long it_indirect_levels;
> + unsigned long it_level_size;
> unsigned long it_offset; /* Offset into global table */
> unsigned long it_base; /* mapped address of tce table */
> unsigned long it_index; /* which iommu table this is */
> diff --git a/arch/powerpc/platforms/powernv/pci-ioda.c b/arch/powerpc/platforms/powernv/pci-ioda.c
> index 59baa15..cc1d09c 100644
> --- a/arch/powerpc/platforms/powernv/pci-ioda.c
> +++ b/arch/powerpc/platforms/powernv/pci-ioda.c
> @@ -1967,13 +1967,17 @@ static long pnv_pci_ioda2_set_window(struct iommu_table_group *table_group,
> table_group);
> struct pnv_phb *phb = pe->phb;
> int64_t rc;
> + const unsigned long size = tbl->it_indirect_levels ?
> + tbl->it_level_size : tbl->it_size;
> const __u64 start_addr = tbl->it_offset << tbl->it_page_shift;
> const __u64 win_size = tbl->it_size << tbl->it_page_shift;
>
> pe_info(pe, "Setting up window at %llx..%llx "
> - "pgsize=0x%x tablesize=0x%lx\n",
> + "pgsize=0x%x tablesize=0x%lx "
> + "levels=%d levelsize=%x\n",
> start_addr, start_addr + win_size - 1,
> - 1UL << tbl->it_page_shift, tbl->it_size << 3);
> + 1UL << tbl->it_page_shift, tbl->it_size << 3,
> + tbl->it_indirect_levels + 1, tbl->it_level_size << 3);
>
> tbl->it_table_group = &pe->table_group;
>
> @@ -1984,9 +1988,9 @@ static long pnv_pci_ioda2_set_window(struct iommu_table_group *table_group,
> rc = opal_pci_map_pe_dma_window(phb->opal_id,
> pe->pe_number,
> pe->pe_number << 1,
> - 1,
> + tbl->it_indirect_levels + 1,
> __pa(tbl->it_base),
> - tbl->it_size << 3,
> + size << 3,
> 1ULL << tbl->it_page_shift);
> if (rc) {
> pe_err(pe, "Failed to configure TCE table, err %ld\n", rc);
> @@ -2099,7 +2103,8 @@ static void pnv_pci_ioda2_setup_dma_pe(struct pnv_phb *phb,
> phb->ioda.m32_pci_base);
>
> rc = pnv_pci_create_table(&pe->table_group, pe->phb->hose->node,
> - 0, IOMMU_PAGE_SHIFT_4K, phb->ioda.m32_pci_base, tbl);
> + 0, IOMMU_PAGE_SHIFT_4K, phb->ioda.m32_pci_base,
> + POWERNV_IOMMU_DEFAULT_LEVELS, tbl);
> if (rc) {
> pe_err(pe, "Failed to create 32-bit TCE table, err %ld", rc);
> return;
> diff --git a/arch/powerpc/platforms/powernv/pci.c b/arch/powerpc/platforms/powernv/pci.c
> index 6bcfad5..fc129c4 100644
> --- a/arch/powerpc/platforms/powernv/pci.c
> +++ b/arch/powerpc/platforms/powernv/pci.c
> @@ -46,6 +46,8 @@
> #define cfg_dbg(fmt...) do { } while(0)
> //#define cfg_dbg(fmt...) printk(fmt)
>
> +#define ROUND_UP(x, n) (((x) + (n) - 1ULL) & ~((n) - 1ULL))

Use the existing ALIGN_UP macro instead of creating a new one.

> #ifdef CONFIG_PCI_MSI
> static int pnv_setup_msi_irqs(struct pci_dev *pdev, int nvec, int type)
> {
> @@ -577,6 +579,19 @@ struct pci_ops pnv_pci_ops = {
> static __be64 *pnv_tce(struct iommu_table *tbl, long idx)
> {
> __be64 *tmp = ((__be64 *)tbl->it_base);
> + int level = tbl->it_indirect_levels;
> + const long shift = ilog2(tbl->it_level_size);
> + unsigned long mask = (tbl->it_level_size - 1) << (level * shift);
> +
> + while (level) {
> + int n = (idx & mask) >> (level * shift);
> + unsigned long tce = be64_to_cpu(tmp[n]);
> +
> + tmp = __va(tce & ~(TCE_PCI_READ | TCE_PCI_WRITE));
> + idx &= ~mask;
> + mask >>= shift;
> + --level;
> + }
>
> return tmp + idx;
> }
> @@ -648,12 +663,18 @@ void pnv_pci_setup_iommu_table(struct iommu_table *tbl,
> }
>
> static __be64 *pnv_alloc_tce_table_pages(int nid, unsigned shift,
> + unsigned levels, unsigned long limit,
> unsigned long *tce_table_allocated)
> {
> struct page *tce_mem = NULL;
> - __be64 *addr;
> + __be64 *addr, *tmp;
> unsigned order = max_t(unsigned, shift, PAGE_SHIFT) - PAGE_SHIFT;
> unsigned long local_allocated = 1UL << (order + PAGE_SHIFT);
> + unsigned entries = 1UL << (shift - 3);
> + long i;
> +
> + if (limit == *tce_table_allocated)
> + return NULL;

If this is for what I think, it seems a bit unsafe. Shouldn't it be
>=, otherwise it could fail to trip if the limit isn't exactly a
>multiple of the bottom level allocation unit.

> tce_mem = alloc_pages_node(nid, GFP_KERNEL, order);
> if (!tce_mem) {
> @@ -662,14 +683,33 @@ static __be64 *pnv_alloc_tce_table_pages(int nid, unsigned shift,
> }
> addr = page_address(tce_mem);
> memset(addr, 0, local_allocated);
> - *tce_table_allocated = local_allocated;
> +
> + --levels;
> + if (!levels) {
> + /* Update tce_table_allocated with bottom level table size only */
> + *tce_table_allocated += local_allocated;
> + return addr;
> + }
> +
> + for (i = 0; i < entries; ++i) {
> + tmp = pnv_alloc_tce_table_pages(nid, shift, levels, limit,
> + tce_table_allocated);

Urgh.. it's a limited depth so it *might* be ok, but recursion is
generally avoided in the kernel, becuase of the very limited stack
size.

> + if (!tmp)
> + break;
> +
> + addr[i] = cpu_to_be64(__pa(tmp) |
> + TCE_PCI_READ | TCE_PCI_WRITE);
> + }

It also seems like it would make sense for this function ti set
it_indirect_levels ant it_level_size, rather than leaving it to the
caller.

> return addr;
> }
>
> +static void pnv_free_tce_table_pages(unsigned long addr, unsigned long size,
> + unsigned level);
> +
> long pnv_pci_create_table(struct iommu_table_group *table_group, int nid,
> __u64 bus_offset, __u32 page_shift, __u64 window_size,
> - struct iommu_table *tbl)
> + __u32 levels, struct iommu_table *tbl)
> {
> void *addr;
> unsigned long tce_table_allocated = 0;
> @@ -678,16 +718,34 @@ long pnv_pci_create_table(struct iommu_table_group *table_group, int nid,
> unsigned table_shift = entries_shift + 3;
> const unsigned long tce_table_size = max(0x1000UL, 1UL << table_shift);
>
> + if (!levels || (levels > POWERNV_IOMMU_MAX_LEVELS))
> + return -EINVAL;
> +
> if ((window_size > memory_hotplug_max()) || !is_power_of_2(window_size))
> return -EINVAL;
>
> + /* Adjust direct table size from window_size and levels */
> + entries_shift = ROUND_UP(entries_shift, levels) / levels;

ROUND_UP() only works if the second parameter is a power of 2. Is
that always true for levels?

For division rounding up, the usual idiom is just ((a + (b - 1)) / b)

> + table_shift = entries_shift + 3;
> + table_shift = max_t(unsigned, table_shift, PAGE_SHIFT);

Does the PAGE_SHIFT rounding make sense any more? I would have
thought you'd round the level size up to page size, rather than the
whole thing.

> /* Allocate TCE table */
> addr = pnv_alloc_tce_table_pages(nid, table_shift,
> - &tce_table_allocated);
> + levels, tce_table_size, &tce_table_allocated);
> + if (!addr)
> + return -ENOMEM;
> +
> + if (tce_table_size != tce_table_allocated) {
> + pnv_free_tce_table_pages((unsigned long) addr,
> + tbl->it_level_size, tbl->it_indirect_levels);
> + return -ENOMEM;
> + }
>
> /* Setup linux iommu table */
> pnv_pci_setup_iommu_table(tbl, addr, tce_table_size, bus_offset,
> page_shift);
> + tbl->it_level_size = 1ULL << (table_shift - 3);
> + tbl->it_indirect_levels = levels - 1;
>
> pr_info("Created TCE table: window size = %08llx, "
> "tablesize = %lx (%lx), start @%08llx\n",
> @@ -697,12 +755,38 @@ long pnv_pci_create_table(struct iommu_table_group *table_group, int nid,
> return 0;
> }
>
> +static void pnv_free_tce_table_pages(unsigned long addr, unsigned long size,
> + unsigned level)
> +{
> + addr &= ~(TCE_PCI_READ | TCE_PCI_WRITE);
> +
> + if (level) {
> + long i;
> + u64 *tmp = (u64 *) addr;
> +
> + for (i = 0; i < size; ++i) {
> + unsigned long hpa = be64_to_cpu(tmp[i]);
> +
> + if (!(hpa & (TCE_PCI_READ | TCE_PCI_WRITE)))
> + continue;
> +
> + pnv_free_tce_table_pages((unsigned long) __va(hpa),
> + size, level - 1);
> + }
> + }
> +
> + free_pages(addr, get_order(size << 3));
> +}
> +
> void pnv_pci_free_table(struct iommu_table *tbl)
> {
> + const unsigned long size = tbl->it_indirect_levels ?
> + tbl->it_level_size : tbl->it_size;
> +
> if (!tbl->it_size)
> return;
>
> - free_pages(tbl->it_base, get_order(tbl->it_size << 3));
> + pnv_free_tce_table_pages(tbl->it_base, size, tbl->it_indirect_levels);
> iommu_reset_table(tbl, "pnv");
> }
>
> diff --git a/arch/powerpc/platforms/powernv/pci.h b/arch/powerpc/platforms/powernv/pci.h
> index e6cbbec..3d1ff584 100644
> --- a/arch/powerpc/platforms/powernv/pci.h
> +++ b/arch/powerpc/platforms/powernv/pci.h
> @@ -218,9 +218,11 @@ int pnv_pci_cfg_write(struct pci_dn *pdn,
> extern void pnv_pci_setup_iommu_table(struct iommu_table *tbl,
> void *tce_mem, u64 tce_size,
> u64 dma_offset, unsigned page_shift);
> +#define POWERNV_IOMMU_DEFAULT_LEVELS 1
> +#define POWERNV_IOMMU_MAX_LEVELS 5
> extern long pnv_pci_create_table(struct iommu_table_group *table_group, int nid,
> __u64 bus_offset, __u32 page_shift, __u64 window_size,
> - struct iommu_table *tbl);
> + __u32 levels, struct iommu_table *tbl);
> extern void pnv_pci_free_table(struct iommu_table *tbl);
> extern void pnv_pci_init_p5ioc2_hub(struct device_node *np);
> extern void pnv_pci_init_ioda_hub(struct device_node *np);

--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson

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