We are adding support for DMA memory pre-registration to be used in
conjunction with VFIO. The idea is that the userspace which is going to
run a guest may want to pre-register a user space memory region so
it all gets pinned once and never goes away. Having this done,
a hypervisor will not have to pin/unpin pages on every DMA map/unmap
request. This is going to help with multiple pinning of the same memory
and in-kernel acceleration of DMA requests.

This adds a list of memory regions to mm_context_t. Each region consists
of a header and a list of physical addresses. This adds API to:
1. register/unregister memory regions;
2. do final cleanup (which puts all pre-registered pages);
3. do userspace to physical address translation;
4. manage a mapped pages counter; when it is zero, it is safe to
unregister the region.

Multiple registration of the same region is allowed, kref is used to
track the number of registrations.

Signed-off-by: Alexey Kardashevskiy <redacted>
---
Changes:
v8:
* s/mm_iommu_table_group_mem_t/struct mm_iommu_table_group_mem_t/
* fixed error fallback look (s/[i]/[j]/)
---
 arch/powerpc/include/asm/mmu-hash64.h      |   3 +
 arch/powerpc/include/asm/mmu_context.h     |  17 +++
 arch/powerpc/mm/Makefile                   |   1 +
 arch/powerpc/mm/mmu_context_hash64.c       |   6 +
 arch/powerpc/mm/mmu_context_hash64_iommu.c | 215 +++++++++++++++++++++++++++++
 5 files changed, 242 insertions(+)
 create mode 100644 arch/powerpc/mm/mmu_context_hash64_iommu.c

diff --git a/arch/powerpc/include/asm/mmu-hash64.h b/arch/powerpc/include/asm/mmu-hash64.h
index 1da6a81..a82f534 100644
--- a/arch/powerpc/include/asm/mmu-hash64.h
+++ b/arch/powerpc/include/asm/mmu-hash64.h

@@ -536,6 +536,9 @@ typedef struct {
 	/* for 4K PTE fragment support */
 	void *pte_frag;
 #endif
+#ifdef CONFIG_SPAPR_TCE_IOMMU
+	struct list_head iommu_group_mem_list;
+#endif

 } mm_context_t;
 
 

diff --git a/arch/powerpc/include/asm/mmu_context.h b/arch/powerpc/include/asm/mmu_context.h
index 73382eb..d6116ca 100644
--- a/arch/powerpc/include/asm/mmu_context.h
+++ b/arch/powerpc/include/asm/mmu_context.h

@@ -16,6 +16,23 @@
  */
 extern int init_new_context(struct task_struct *tsk, struct mm_struct *mm);
 extern void destroy_context(struct mm_struct *mm);
+#ifdef CONFIG_SPAPR_TCE_IOMMU
+struct mm_iommu_table_group_mem_t;
+
+extern bool mm_iommu_preregistered(void);
+extern long mm_iommu_alloc(unsigned long ua, unsigned long entries,
+		struct mm_iommu_table_group_mem_t **pmem);
+extern struct mm_iommu_table_group_mem_t *mm_iommu_get(unsigned long ua,
+		unsigned long entries);
+extern long mm_iommu_put(struct mm_iommu_table_group_mem_t *mem);
+extern void mm_iommu_cleanup(mm_context_t *ctx);
+extern struct mm_iommu_table_group_mem_t *mm_iommu_lookup(unsigned long ua,
+		unsigned long size);
+extern long mm_iommu_ua_to_hpa(struct mm_iommu_table_group_mem_t *mem,
+		unsigned long ua, unsigned long *hpa);
+extern long mm_iommu_mapped_update(struct mm_iommu_table_group_mem_t *mem,
+		bool inc);
+#endif
 
 extern void switch_mmu_context(struct mm_struct *prev, struct mm_struct *next);
 extern void switch_slb(struct task_struct *tsk, struct mm_struct *mm);

diff --git a/arch/powerpc/mm/Makefile b/arch/powerpc/mm/Makefile
index 9c8770b..e216704 100644
--- a/arch/powerpc/mm/Makefile
+++ b/arch/powerpc/mm/Makefile

@@ -36,3 +36,4 @@ obj-$(CONFIG_PPC_SUBPAGE_PROT)	+= subpage-prot.o
 obj-$(CONFIG_NOT_COHERENT_CACHE) += dma-noncoherent.o
 obj-$(CONFIG_HIGHMEM)		+= highmem.o
 obj-$(CONFIG_PPC_COPRO_BASE)	+= copro_fault.o
+obj-$(CONFIG_SPAPR_TCE_IOMMU)	+= mmu_context_hash64_iommu.o

diff --git a/arch/powerpc/mm/mmu_context_hash64.c b/arch/powerpc/mm/mmu_context_hash64.c
index 178876ae..eb3080c 100644
--- a/arch/powerpc/mm/mmu_context_hash64.c
+++ b/arch/powerpc/mm/mmu_context_hash64.c

@@ -89,6 +89,9 @@ int init_new_context(struct task_struct *tsk, struct mm_struct *mm)
 #ifdef CONFIG_PPC_64K_PAGES
 	mm->context.pte_frag = NULL;
 #endif
+#ifdef CONFIG_SPAPR_TCE_IOMMU
+	INIT_LIST_HEAD_RCU(&mm->context.iommu_group_mem_list);
+#endif
 	return 0;
 }
 

@@ -132,6 +135,9 @@ static inline void destroy_pagetable_page(struct mm_struct *mm)
 
 void destroy_context(struct mm_struct *mm)
 {
+#ifdef CONFIG_SPAPR_TCE_IOMMU
+	mm_iommu_cleanup(&mm->context);
+#endif
 
 #ifdef CONFIG_PPC_ICSWX
 	drop_cop(mm->context.acop, mm);

diff --git a/arch/powerpc/mm/mmu_context_hash64_iommu.c b/arch/powerpc/mm/mmu_context_hash64_iommu.c
new file mode 100644
index 0000000..af7668c
--- /dev/null
+++ b/arch/powerpc/mm/mmu_context_hash64_iommu.c

@@ -0,0 +1,215 @@
+/*
+ *  IOMMU helpers in MMU context.
+ *
+ *  Copyright (C) 2015 IBM Corp. <aik@ozlabs.ru>
+ *
+ *  This program is free software; you can redistribute it and/or
+ *  modify it under the terms of the GNU General Public License
+ *  as published by the Free Software Foundation; either version
+ *  2 of the License, or (at your option) any later version.
+ *
+ */
+
+#include <linux/sched.h>
+#include <linux/slab.h>
+#include <linux/rculist.h>
+#include <linux/vmalloc.h>
+#include <linux/kref.h>
+#include <asm/mmu_context.h>
+
+struct mm_iommu_table_group_mem_t {
+	struct list_head next;
+	struct rcu_head rcu;
+	struct kref kref;	/* one reference per VFIO container */
+	atomic_t mapped;	/* number of currently mapped pages */
+	u64 ua;			/* userspace address */
+	u64 entries;		/* number of entries in hpas[] */