[PATCH kernel v7 02/20] powerpc/mm/iommu/vfio_spapr_tce: Change mm_iommu_get to reference a region

Alexey Kardashevskiy
2018-12-20T08:23:32Z

Normally mm_iommu_get() should add a reference and mm_iommu_put() should
remove it. However historically mm_iommu_find() does the referencing and
mm_iommu_get() is doing allocation and referencing.

We are going to add another helper to preregister device memory so
instead of having mm_iommu_new() (which pre-registers the normal memory
and references the region), we need separate helpers for pre-registering
and referencing.

This renames:
- mm_iommu_get to mm_iommu_new;
- mm_iommu_find to mm_iommu_get.

This changes mm_iommu_get() to reference the region so the name now
reflects what it does.

This removes the check for exact match from mm_iommu_new() as we want it
to fail on existing regions; mm_iommu_get() should be used instead.

Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
---
Changes:
v5:
* fixed a bug with uninitialized @found in tce_iommu_unregister_pages()
* reworded the commit log

v4:
* squashed "powerpc/mm/iommu: Make mm_iommu_new() fail on existing regions" into this

v2:
* merged 2 patches into one
---
arch/powerpc/include/asm/mmu_context.h | 4 +--
arch/powerpc/mm/mmu_context_iommu.c | 19 +++++++-------
drivers/vfio/vfio_iommu_spapr_tce.c | 35 +++++++++++++++++---------
3 files changed, 34 insertions(+), 24 deletions(-)

diff --git a/arch/powerpc/include/asm/mmu_context.h b/arch/powerpc/include/asm/mmu_context.h
index c05efd2..268e112 100644
--- a/arch/powerpc/include/asm/mmu_context.h
+++ b/arch/powerpc/include/asm/mmu_context.h
@@ -21,7 +21,7 @@ struct mm_iommu_table_group_mem_t;

extern int isolate_lru_page(struct page *page); /* from internal.h */
extern bool mm_iommu_preregistered(struct mm_struct *mm);
-extern long mm_iommu_get(struct mm_struct *mm,
+extern long mm_iommu_new(struct mm_struct *mm,
unsigned long ua, unsigned long entries,
struct mm_iommu_table_group_mem_t **pmem);
extern long mm_iommu_put(struct mm_struct *mm,
@@ -32,7 +32,7 @@ extern struct mm_iommu_table_group_mem_t *mm_iommu_lookup(struct mm_struct *mm,
unsigned long ua, unsigned long size);
extern struct mm_iommu_table_group_mem_t *mm_iommu_lookup_rm(
struct mm_struct *mm, unsigned long ua, unsigned long size);
-extern struct mm_iommu_table_group_mem_t *mm_iommu_find(struct mm_struct *mm,
+extern struct mm_iommu_table_group_mem_t *mm_iommu_get(struct mm_struct *mm,
unsigned long ua, unsigned long entries);
extern long mm_iommu_ua_to_hpa(struct mm_iommu_table_group_mem_t *mem,
unsigned long ua, unsigned int pageshift, unsigned long *hpa);
diff --git a/arch/powerpc/mm/mmu_context_iommu.c b/arch/powerpc/mm/mmu_context_iommu.c
index 0741d90..25a4b7f7 100644
--- a/arch/powerpc/mm/mmu_context_iommu.c
+++ b/arch/powerpc/mm/mmu_context_iommu.c
@@ -89,7 +89,7 @@ bool mm_iommu_preregistered(struct mm_struct *mm)
}
EXPORT_SYMBOL_GPL(mm_iommu_preregistered);

-long mm_iommu_get(struct mm_struct *mm, unsigned long ua, unsigned long entries,
+long mm_iommu_new(struct mm_struct *mm, unsigned long ua, unsigned long entries,
struct mm_iommu_table_group_mem_t **pmem)
{
struct mm_iommu_table_group_mem_t *mem;
@@ -100,12 +100,6 @@ long mm_iommu_get(struct mm_struct *mm, unsigned long ua, unsigned long entries,

list_for_each_entry_rcu(mem, &mm->context.iommu_group_mem_list,
next) {
- if ((mem->ua == ua) && (mem->entries == entries)) {
- ++mem->used;
- *pmem = mem;
- goto unlock_exit;
- }
-
/* Overlap? */
if ((mem->ua < (ua + (entries << PAGE_SHIFT))) &&
(ua < (mem->ua +
@@ -192,7 +186,7 @@ long mm_iommu_get(struct mm_struct *mm, unsigned long ua, unsigned long entries,

return ret;
}
-EXPORT_SYMBOL_GPL(mm_iommu_get);
+EXPORT_SYMBOL_GPL(mm_iommu_new);

static void mm_iommu_unpin(struct mm_iommu_table_group_mem_t *mem)
{
@@ -308,21 +302,26 @@ struct mm_iommu_table_group_mem_t *mm_iommu_lookup_rm(struct mm_struct *mm,
return ret;
}

-struct mm_iommu_table_group_mem_t *mm_iommu_find(struct mm_struct *mm,
+struct mm_iommu_table_group_mem_t *mm_iommu_get(struct mm_struct *mm,
unsigned long ua, unsigned long entries)
{
struct mm_iommu_table_group_mem_t *mem, *ret = NULL;

+ mutex_lock(&mem_list_mutex);
+
list_for_each_entry_rcu(mem, &mm->context.iommu_group_mem_list, next) {
if ((mem->ua == ua) && (mem->entries == entries)) {
ret = mem;
+ ++mem->used;
break;
}
}

+ mutex_unlock(&mem_list_mutex);
+
return ret;
}
-EXPORT_SYMBOL_GPL(mm_iommu_find);
+EXPORT_SYMBOL_GPL(mm_iommu_get);

long mm_iommu_ua_to_hpa(struct mm_iommu_table_group_mem_t *mem,
unsigned long ua, unsigned int pageshift, unsigned long *hpa)
diff --git a/drivers/vfio/vfio_iommu_spapr_tce.c b/drivers/vfio/vfio_iommu_spapr_tce.c
index ad63725..1d8b889 100644
--- a/drivers/vfio/vfio_iommu_spapr_tce.c
+++ b/drivers/vfio/vfio_iommu_spapr_tce.c
@@ -152,11 +152,12 @@ static long tce_iommu_unregister_pages(struct tce_container *container,
struct mm_iommu_table_group_mem_t *mem;
struct tce_iommu_prereg *tcemem;
bool found = false;
+ long ret;

if ((vaddr & ~PAGE_MASK) || (size & ~PAGE_MASK))
return -EINVAL;

- mem = mm_iommu_find(container->mm, vaddr, size >> PAGE_SHIFT);
+ mem = mm_iommu_get(container->mm, vaddr, size >> PAGE_SHIFT);
if (!mem)
return -ENOENT;

@@ -168,9 +169,13 @@ static long tce_iommu_unregister_pages(struct tce_container *container,
}

if (!found)
- return -ENOENT;
+ ret = -ENOENT;
+ else
+ ret = tce_iommu_prereg_free(container, tcemem);

- return tce_iommu_prereg_free(container, tcemem);
+ mm_iommu_put(container->mm, mem);
+
+ return ret;
}

static long tce_iommu_register_pages(struct tce_container *container,
@@ -185,22 +190,24 @@ static long tce_iommu_register_pages(struct tce_container *container,
((vaddr + size) < vaddr))
return -EINVAL;

- mem = mm_iommu_find(container->mm, vaddr, entries);
+ mem = mm_iommu_get(container->mm, vaddr, entries);
if (mem) {
list_for_each_entry(tcemem, &container->prereg_list, next) {
- if (tcemem->mem == mem)
- return -EBUSY;
+ if (tcemem->mem == mem) {
+ ret = -EBUSY;
+ goto put_exit;
+ }
}
+ } else {
+ ret = mm_iommu_new(container->mm, vaddr, entries, &mem);
+ if (ret)
+ return ret;
}

- ret = mm_iommu_get(container->mm, vaddr, entries, &mem);
- if (ret)
- return ret;
-
tcemem = kzalloc(sizeof(*tcemem), GFP_KERNEL);
if (!tcemem) {
- mm_iommu_put(container->mm, mem);
- return -ENOMEM;
+ ret = -ENOMEM;
+ goto put_exit;
}

tcemem->mem = mem;
@@ -209,6 +216,10 @@ static long tce_iommu_register_pages(struct tce_container *container,
container->enabled = true;

return 0;
+
+put_exit:
+ mm_iommu_put(container->mm, mem);
+ return ret;
}

static bool tce_page_is_contained(struct page *page, unsigned page_shift)
--
2.17.1