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

From: David Gibson <[email-masked]>
Date: Thu, 30 Apr 2015 14:37:50 +1000

On Wed, Apr 29, 2015 at 07:44:20PM +1000, Alexey Kardashevskiy wrote:
> 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" ;)

Yeah, fair enough ;)

> 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?

On further consideration, yes, I think you're right.

> >>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.

So you "create" once, then "set" it to one or more table_groups?  It
seems odd that "create" is a table_group callback in that case.

> >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.

So I think the scheme I suggested in reply to an earlier patch helps
this.  With that the lifetime of the struct iommu_table represents the
lifetime of the TCE table in the hardware sense as well, which I think
makes things clearer.

> 
> 
> >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.

Ah, ok.

-- 
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