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

Alexey Kardashevskiy
2015-05-01T09:49:06Z

On 04/29/2015 03:04 PM, David Gibson wrote:
> 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.

Ok. I knew it existed, it is just _ALIGN_UP (with an underscore) and
PPC-only - this is why I did not find it :)

>> #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.

Good point, will fix.

>> 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.

It is 5 levels max 7 64bit values, there should be room for it. Avoiding
recursion here - I can do that but it is going to look ugly :-/

>> + 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.

Mmm. Sure? It calls itself in recursion, does not seem like it is the right
place for setting up it_indirect_levels ant it_level_size.

>> 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)

Yes, I think this is what I actually wanted.

>> + 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.

At this point in the code @table_shift is level_shift but it is not that
obvious :) I'll rework it. Thanks.

>> /* 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);
>

--
Alexey