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SubjectRe: [PATCH kernel v11 27/34] powerpc/powernv: Implement multilevel TCE tables
On Fri, May 29, 2015 at 06:44:51PM +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_ioda2_table_alloc_pages() and pnv_pci_ioda2_table_free_pages()
> helpers.
>
> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
> ---
> Changes:
> v10:
> * fixed multiple comments received for v9
>
> 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 | 98 ++++++++++++++++++++++++++++---
> arch/powerpc/platforms/powernv/pci.c | 13 ++++
> 3 files changed, 104 insertions(+), 9 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/iommu.h b/arch/powerpc/include/asm/iommu.h
> index 4636734..706cfc0 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 fda01c1..68ffc7a 100644
> --- a/arch/powerpc/platforms/powernv/pci-ioda.c
> +++ b/arch/powerpc/platforms/powernv/pci-ioda.c
> @@ -49,6 +49,9 @@
> /* 256M DMA window, 4K TCE pages, 8 bytes TCE */
> #define TCE32_TABLE_SIZE ((0x10000000 / 0x1000) * 8)
>
> +#define POWERNV_IOMMU_DEFAULT_LEVELS 1
> +#define POWERNV_IOMMU_MAX_LEVELS 5
> +
> static void pnv_pci_ioda2_table_free_pages(struct iommu_table *tbl);
>
> static void pe_level_printk(const struct pnv_ioda_pe *pe, const char *level,
> @@ -1975,6 +1978,8 @@ 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;
>
> @@ -1989,9 +1994,9 @@ 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,
> IOMMU_PAGE_SIZE(tbl));
> if (rc) {
> pe_err(pe, "Failed to configure TCE table, err %ld\n", rc);
> @@ -2071,11 +2076,19 @@ static void pnv_pci_ioda_setup_opal_tce_kill(struct pnv_phb *phb)
> phb->ioda.tce_inval_reg = ioremap(phb->ioda.tce_inval_reg_phys, 8);
> }
>
> -static __be64 *pnv_pci_ioda2_table_do_alloc_pages(int nid, unsigned shift)
> +static __be64 *pnv_pci_ioda2_table_do_alloc_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 (*tce_table_allocated >= limit)
> + return NULL;

I'm not quite clear what case this limit logic is trying to catch.

>
> tce_mem = alloc_pages_node(nid, GFP_KERNEL, order);
> if (!tce_mem) {
> @@ -2083,31 +2096,69 @@ static __be64 *pnv_pci_ioda2_table_do_alloc_pages(int nid, unsigned shift)
> return NULL;
> }
> addr = page_address(tce_mem);
> - memset(addr, 0, 1UL << (order + PAGE_SHIFT));
> + memset(addr, 0, local_allocated);
> +
> + --levels;
> + if (!levels) {
> + *tce_table_allocated += local_allocated;
> + return addr;
> + }
> +
> + for (i = 0; i < entries; ++i) {
> + tmp = pnv_pci_ioda2_table_do_alloc_pages(nid, shift,
> + levels, limit, tce_table_allocated);
> + if (!tmp)
> + break;
> +
> + addr[i] = cpu_to_be64(__pa(tmp) |
> + TCE_PCI_READ | TCE_PCI_WRITE);
> + }
>
> return addr;
> }
>
> +static void pnv_pci_ioda2_table_do_free_pages(unsigned long addr,
> + unsigned long size, unsigned level);
> +
> static long pnv_pci_ioda2_table_alloc_pages(int nid, __u64 bus_offset,
> - __u32 page_shift, __u64 window_size, struct iommu_table *tbl)
> + __u32 page_shift, __u64 window_size, __u32 levels,
> + struct iommu_table *tbl)
> {
> void *addr;
> + unsigned long tce_table_allocated = 0, level_shift;
> const unsigned window_shift = ilog2(window_size);
> unsigned entries_shift = window_shift - page_shift;
> unsigned table_shift = max_t(unsigned, entries_shift + 3, PAGE_SHIFT);
> const unsigned long tce_table_size = 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 = (entries_shift + levels - 1) / levels;
> + level_shift = entries_shift + 3;
> + level_shift = max_t(unsigned, level_shift, PAGE_SHIFT);
> +
> /* Allocate TCE table */
> - addr = pnv_pci_ioda2_table_do_alloc_pages(nid, table_shift);
> + addr = pnv_pci_ioda2_table_do_alloc_pages(nid, level_shift,
> + levels, tce_table_size, &tce_table_allocated);
> if (!addr)
> return -ENOMEM;

If the do_alloc_pages hits the limit partway through its recursion
this will leak memory.

>
> + if (tce_table_size > tce_table_allocated) {
> + pnv_pci_ioda2_table_do_free_pages((unsigned long) addr,
> + 1ULL << (level_shift - 3), levels - 1);
> + return -ENOMEM;

The logic here doesn't quite make sense to me. Is this trying to
catch the case where do_alloc_pages hit the limit before completing?
Comparing the total memory allocated by all the levels to the amount
that would be allocated by a linear table doesn't seem like a useful
thing to do.

> + }
> +
> /* Setup linux iommu table */
> pnv_pci_setup_iommu_table(tbl, addr, tce_table_size, bus_offset,
> page_shift);
> + tbl->it_level_size = 1ULL << (level_shift - 3);
> + tbl->it_indirect_levels = levels - 1;
>
> pr_devel("Created TCE table: ws=%08llx ts=%lx @%08llx\n",
> window_size, tce_table_size, bus_offset);
> @@ -2115,12 +2166,40 @@ static long pnv_pci_ioda2_table_alloc_pages(int nid, __u64 bus_offset,
> return 0;
> }
>
> +static void pnv_pci_ioda2_table_do_free_pages(unsigned long addr,

Since addr is a virtual address, not a physical one, it should be
passed as a pointer.

> + 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_pci_ioda2_table_do_free_pages(
> + (unsigned long) __va(hpa),
> + size, level - 1);
> + }
> + }
> +
> + free_pages(addr, get_order(size << 3));
> +}
> +
> static void pnv_pci_ioda2_table_free_pages(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_pci_ioda2_table_do_free_pages(tbl->it_base, size,
> + tbl->it_indirect_levels);
> }
>
> static void pnv_pci_ioda2_setup_dma_pe(struct pnv_phb *phb,
> @@ -2148,7 +2227,8 @@ static void pnv_pci_ioda2_setup_dma_pe(struct pnv_phb *phb,
>
> /* Setup linux iommu table */
> rc = pnv_pci_ioda2_table_alloc_pages(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);
> goto fail;
> diff --git a/arch/powerpc/platforms/powernv/pci.c b/arch/powerpc/platforms/powernv/pci.c
> index dce3bfd..d4e59f7 100644
> --- a/arch/powerpc/platforms/powernv/pci.c
> +++ b/arch/powerpc/platforms/powernv/pci.c
> @@ -575,6 +575,19 @@ 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;
> }

--
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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