Subject: Re: [PATCH kernel v9 23/32] powerpc/powernv/ioda: Define and implement DMA table/window management callbacks

From: Alexey Kardashevskiy <[email-masked]>
Date: Wed, 29 Apr 2015 19:44:20 +1000

On 04/29/2015 03:30 PM, David Gibson wrote:
> On Sat, Apr 25, 2015 at 10:14:47PM +1000, Alexey Kardashevskiy wrote:
>> This extends iommu_table_group_ops by a set of callbacks to support
>> dynamic DMA windows management.
>>
>> create_table() creates a TCE table with specific parameters.
>> it receives iommu_table_group to know nodeid in order to allocate
>> TCE table memory closer to the PHB. The exact format of allocated
>> multi-level table might be also specific to the PHB model (not
>> the case now though).
>> This callback calculated the DMA window offset on a PCI bus from @num
>> and stores it in a just created table.
>>
>> set_window() sets the window at specified TVT index + @num on PHB.
>>
>> unset_window() unsets the window from specified TVT.
>>
>> This adds a free() callback to iommu_table_ops to free the memory
>> (potentially a tree of tables) allocated for the TCE table.
>
> Doesn't the free callback belong with the previous patch introducing
> multi-level tables?

If I did that, you would say "why is it here if nothing calls it" on 
"multilevel" patch and "I see the allocation but I do not see memory 
release" ;)

I need some rule of thumb here. I think it is a bit cleaner if the same 
patch adds a callback for memory allocation and its counterpart, no?

>> create_table() and free() are supposed to be called once per
>> VFIO container and set_window()/unset_window() are supposed to be
>> called for every group in a container.
>>
>> This adds IOMMU capabilities to iommu_table_group such as default
>> 32bit window parameters and others.
>>
>> Signed-off-by: Alexey Kardashevskiy <[email-masked]>
>> ---
>>   arch/powerpc/include/asm/iommu.h            | 19 ++++++++
>>   arch/powerpc/platforms/powernv/pci-ioda.c   | 75 ++++++++++++++++++++++++++---
>>   arch/powerpc/platforms/powernv/pci-p5ioc2.c | 12 +++--
>>   3 files changed, 96 insertions(+), 10 deletions(-)
>>
>> diff --git a/arch/powerpc/include/asm/iommu.h b/arch/powerpc/include/asm/iommu.h
>> index 0f50ee2..7694546 100644
>> --- a/arch/powerpc/include/asm/iommu.h
>> +++ b/arch/powerpc/include/asm/iommu.h
>> @@ -70,6 +70,7 @@ struct iommu_table_ops {
>>   	/* get() returns a physical address */
>>   	unsigned long (*get)(struct iommu_table *tbl, long index);
>>   	void (*flush)(struct iommu_table *tbl);
>> +	void (*free)(struct iommu_table *tbl);
>>   };
>>
>>   /* These are used by VIO */
>> @@ -148,6 +149,17 @@ extern struct iommu_table *iommu_init_table(struct iommu_table * tbl,
>>   struct iommu_table_group;
>>
>>   struct iommu_table_group_ops {
>> +	long (*create_table)(struct iommu_table_group *table_group,
>> +			int num,
>> +			__u32 page_shift,
>> +			__u64 window_size,
>> +			__u32 levels,
>> +			struct iommu_table *tbl);
>> +	long (*set_window)(struct iommu_table_group *table_group,
>> +			int num,
>> +			struct iommu_table *tblnew);
>> +	long (*unset_window)(struct iommu_table_group *table_group,
>> +			int num);
>>   	/*
>>   	 * Switches ownership from the kernel itself to an external
>>   	 * user. While onwership is taken, the kernel cannot use IOMMU itself.
>> @@ -160,6 +172,13 @@ struct iommu_table_group {
>>   #ifdef CONFIG_IOMMU_API
>>   	struct iommu_group *group;
>>   #endif
>> +	/* Some key properties of IOMMU */
>> +	__u32 tce32_start;
>> +	__u32 tce32_size;
>> +	__u64 pgsizes; /* Bitmap of supported page sizes */
>> +	__u32 max_dynamic_windows_supported;
>> +	__u32 max_levels;
>
> With this information, table_group seems even more like a bad name.
> "iommu_state" maybe?

Please, no. We will never come to agreement then :( And "iommu_state" is 
too general anyway, it won't pass.

>>   	struct iommu_table tables[IOMMU_TABLE_GROUP_MAX_TABLES];
>>   	struct iommu_table_group_ops *ops;
>>   };
>> diff --git a/arch/powerpc/platforms/powernv/pci-ioda.c b/arch/powerpc/platforms/powernv/pci-ioda.c
>> index cc1d09c..4828837 100644
>> --- a/arch/powerpc/platforms/powernv/pci-ioda.c
>> +++ b/arch/powerpc/platforms/powernv/pci-ioda.c
>> @@ -24,6 +24,7 @@
>>   #include <linux/msi.h>
>>   #include <linux/memblock.h>
>>   #include <linux/iommu.h>
>> +#include <linux/sizes.h>
>>
>>   #include <asm/sections.h>
>>   #include <asm/io.h>
>> @@ -1846,6 +1847,7 @@ static struct iommu_table_ops pnv_ioda2_iommu_ops = {
>>   #endif
>>   	.clear = pnv_ioda2_tce_free,
>>   	.get = pnv_tce_get,
>> +	.free = pnv_pci_free_table,
>>   };
>>
>>   static void pnv_pci_ioda_setup_opal_tce_kill(struct pnv_phb *phb,
>> @@ -1936,6 +1938,8 @@ static void pnv_pci_ioda_setup_dma_pe(struct pnv_phb *phb,
>>   				 TCE_PCI_SWINV_PAIR);
>>
>>   	tbl->it_ops = &pnv_ioda1_iommu_ops;
>> +	pe->table_group.tce32_start = tbl->it_offset << tbl->it_page_shift;
>> +	pe->table_group.tce32_size = tbl->it_size << tbl->it_page_shift;
>>   	iommu_init_table(tbl, phb->hose->node);
>>
>>   	if (pe->flags & PNV_IODA_PE_DEV) {
>> @@ -1961,7 +1965,7 @@ static void pnv_pci_ioda_setup_dma_pe(struct pnv_phb *phb,
>>   }
>>
>>   static long pnv_pci_ioda2_set_window(struct iommu_table_group *table_group,
>> -		struct iommu_table *tbl)
>> +		int num, struct iommu_table *tbl)
>>   {
>>   	struct pnv_ioda_pe *pe = container_of(table_group, struct pnv_ioda_pe,
>>   			table_group);
>> @@ -1972,9 +1976,10 @@ static long pnv_pci_ioda2_set_window(struct iommu_table_group *table_group,
>>   	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 "
>> +	pe_info(pe, "Setting up window#%d at %llx..%llx "
>>   			"pgsize=0x%x tablesize=0x%lx "
>>   			"levels=%d levelsize=%x\n",
>> +			num,
>>   			start_addr, start_addr + win_size - 1,
>>   			1UL << tbl->it_page_shift, tbl->it_size << 3,
>>   			tbl->it_indirect_levels + 1, tbl->it_level_size << 3);
>> @@ -1987,7 +1992,7 @@ 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,
>> +			(pe->pe_number << 1) + num,
>
> Heh, yes, well, that makes it rather clear that only 2 tables are possible.
>
>>   			tbl->it_indirect_levels + 1,
>>   			__pa(tbl->it_base),
>>   			size << 3,
>> @@ -2000,7 +2005,7 @@ static long pnv_pci_ioda2_set_window(struct iommu_table_group *table_group,
>>   	pnv_pci_ioda2_tvt_invalidate(pe);
>>
>>   	/* Store fully initialized *tbl (may be external) in PE */
>> -	pe->table_group.tables[0] = *tbl;
>> +	pe->table_group.tables[num] = *tbl;
>
> I'm a bit confused by this whole set_window thing.  Is the idea that
> with multiple groups in a container you have multiple table_group s
> each with different copies of the iommu_table structures, but pointing
> to the same actual TCE entries (it_base)?

Yes.

> It seems to me not terribly
> obvious when you "create" a table and when you "set" a window.

A table is not attached anywhere until its address is programmed (in 
set_window()) to the hardware, it is just a table in memory. For 
POWER8/IODA2, I create a table before I attach any group to a container, 
then I program this table to every attached container, right now it is done 
in container's attach_group(). So later we can hotplug any host PCI device 
to a container - it will program same TCE table to every new group in the 
container.

> It's also kind of hard to assess whether the relative lifetimes are
> correct of the table_group, struct iommu_table and the actual TCE tables.

That is true. Do not know how to improve this though.

> Would it make more sense for table_group to become the
> non-vfio-specific counterpart to the vfio container?
> i.e. representing one set of DMA mappings, which one or more PEs could
> be bound to.

table_group is embedded into PE and table/table_group callbacks access PE 
when invalidating TCE table. So I will need something to access PE. Or just 
have an array of 2 iommu_table.

>
>>   	return 0;
>>   fail:
>> @@ -2061,6 +2066,53 @@ static void pnv_pci_ioda2_setup_bypass_pe(struct pnv_phb *phb,
>>   }
>>
>>   #ifdef CONFIG_IOMMU_API
>> +static long pnv_pci_ioda2_create_table(struct iommu_table_group *table_group,
>> +		int num, __u32 page_shift, __u64 window_size, __u32 levels,
>> +		struct iommu_table *tbl)
>> +{
>> +	struct pnv_ioda_pe *pe = container_of(table_group, struct pnv_ioda_pe,
>> +			table_group);
>> +	int nid = pe->phb->hose->node;
>> +	__u64 bus_offset = num ? pe->tce_bypass_base : 0;
>> +	long ret;
>> +
>> +	ret = pnv_pci_create_table(table_group, nid, bus_offset, page_shift,
>> +			window_size, levels, tbl);
>> +	if (ret)
>> +		return ret;
>> +
>> +	tbl->it_ops = &pnv_ioda2_iommu_ops;
>> +	if (pe->tce_inval_reg)
>> +		tbl->it_type |= (TCE_PCI_SWINV_CREATE | TCE_PCI_SWINV_FREE);
>> +
>> +	return 0;
>> +}
>> +
>> +static long pnv_pci_ioda2_unset_window(struct iommu_table_group *table_group,
>> +		int num)
>> +{
>> +	struct pnv_ioda_pe *pe = container_of(table_group, struct pnv_ioda_pe,
>> +			table_group);
>> +	struct pnv_phb *phb = pe->phb;
>> +	struct iommu_table *tbl = &pe->table_group.tables[num];
>> +	long ret;
>> +
>> +	pe_info(pe, "Removing DMA window #%d\n", num);
>> +
>> +	ret = opal_pci_map_pe_dma_window(phb->opal_id, pe->pe_number,
>> +			(pe->pe_number << 1) + num,
>> +			0/* levels */, 0/* table address */,
>> +			0/* table size */, 0/* page size */);
>> +	if (ret)
>> +		pe_warn(pe, "Unmapping failed, ret = %ld\n", ret);
>> +	else
>> +		pnv_pci_ioda2_tvt_invalidate(pe);
>> +
>> +	memset(tbl, 0, sizeof(*tbl));
>> +
>> +	return ret;
>> +}
>> +
>>   static void pnv_ioda2_take_ownership(struct iommu_table_group *table_group)
>>   {
>>   	struct pnv_ioda_pe *pe = container_of(table_group, struct pnv_ioda_pe,
>> @@ -2080,6 +2132,9 @@ static void pnv_ioda2_release_ownership(struct iommu_table_group *table_group)
>>   }
>>
>>   static struct iommu_table_group_ops pnv_pci_ioda2_ops = {
>> +	.create_table = pnv_pci_ioda2_create_table,
>> +	.set_window = pnv_pci_ioda2_set_window,
>> +	.unset_window = pnv_pci_ioda2_unset_window,
>>   	.take_ownership = pnv_ioda2_take_ownership,
>>   	.release_ownership = pnv_ioda2_release_ownership,
>>   };
>> @@ -2102,8 +2157,16 @@ static void pnv_pci_ioda2_setup_dma_pe(struct pnv_phb *phb,
>>   	pe_info(pe, "Setting up 32-bit TCE table at 0..%08x\n",
>>   		phb->ioda.m32_pci_base);
>>
>> +	pe->table_group.tce32_start = 0;
>> +	pe->table_group.tce32_size = phb->ioda.m32_pci_base;
>> +	pe->table_group.max_dynamic_windows_supported =
>> +			IOMMU_TABLE_GROUP_MAX_TABLES;
>> +	pe->table_group.max_levels = POWERNV_IOMMU_MAX_LEVELS;
>> +	pe->table_group.pgsizes = SZ_4K | SZ_64K | SZ_16M;
>> +
>>   	rc = pnv_pci_create_table(&pe->table_group, pe->phb->hose->node,
>> -			0, IOMMU_PAGE_SHIFT_4K, phb->ioda.m32_pci_base,
>> +			pe->table_group.tce32_start, IOMMU_PAGE_SHIFT_4K,
>> +			pe->table_group.tce32_size,
>>   			POWERNV_IOMMU_DEFAULT_LEVELS, tbl);
>>   	if (rc) {
>>   		pe_err(pe, "Failed to create 32-bit TCE table, err %ld", rc);
>> @@ -2119,7 +2182,7 @@ static void pnv_pci_ioda2_setup_dma_pe(struct pnv_phb *phb,
>>   	pe->table_group.ops = &pnv_pci_ioda2_ops;
>>   #endif
>>
>> -	rc = pnv_pci_ioda2_set_window(&pe->table_group, tbl);
>> +	rc = pnv_pci_ioda2_set_window(&pe->table_group, 0, tbl);
>>   	if (rc) {
>>   		pe_err(pe, "Failed to configure 32-bit TCE table,"
>>   		       " err %ld\n", rc);
>> diff --git a/arch/powerpc/platforms/powernv/pci-p5ioc2.c b/arch/powerpc/platforms/powernv/pci-p5ioc2.c
>> index 7a6fd92..d9de4c7 100644
>> --- a/arch/powerpc/platforms/powernv/pci-p5ioc2.c
>> +++ b/arch/powerpc/platforms/powernv/pci-p5ioc2.c
>> @@ -116,6 +116,8 @@ static void __init pnv_pci_init_p5ioc2_phb(struct device_node *np, u64 hub_id,
>>   	u64 phb_id;
>>   	int64_t rc;
>>   	static int primary = 1;
>> +	struct iommu_table_group *table_group;
>> +	struct iommu_table *tbl;
>>
>>   	pr_info(" Initializing p5ioc2 PHB %s\n", np->full_name);
>>
>> @@ -181,14 +183,16 @@ static void __init pnv_pci_init_p5ioc2_phb(struct device_node *np, u64 hub_id,
>>   	pnv_pci_init_p5ioc2_msis(phb);
>>
>>   	/* Setup iommu */
>> -	phb->p5ioc2.table_group.tables[0].it_table_group =
>> -			&phb->p5ioc2.table_group;
>> +	table_group = &phb->p5ioc2.table_group;
>> +	tbl = &phb->p5ioc2.table_group.tables[0];
>> +	tbl->it_table_group = table_group;
>>
>>   	/* Setup TCEs */
>>   	phb->dma_dev_setup = pnv_pci_p5ioc2_dma_dev_setup;
>> -	pnv_pci_setup_iommu_table(&phb->p5ioc2.table_group.tables[0],
>> -				  tce_mem, tce_size, 0,
>> +	pnv_pci_setup_iommu_table(tbl, tce_mem, tce_size, 0,
>>   				  IOMMU_PAGE_SHIFT_4K);
>> +	table_group->tce32_start = tbl->it_offset << tbl->it_page_shift;
>> +	table_group->tce32_size = tbl->it_size << tbl->it_page_shift;
>
> Doesn't pgsizes need to be set here (although it will only include 4K,
> I'm assuming).

No, pgsizes are not returned to the userspace for p5ioc2/ioda1 as they do 
not support DDW. No pgsize => no DDW.

>>   }
>>
>>   void __init pnv_pci_init_p5ioc2_hub(struct device_node *np)
>

-- 
Alexey