On 13/10/16 13:25, David Gibson wrote:
> On Wed, Oct 12, 2016 at 03:58:27PM +1100, Alexey Kardashevskiy wrote:
>> In some situations the userspace memory context may live longer than
>> the userspace process itself so if we need to do proper memory context
>> cleanup, we better cache @mm and use it later when the process is gone
>> (@current or @current->mm are NULL).
>>
>> This changes mm_iommu_xxx API to receive mm_struct instead of using one
>> from @current.
>>
>> This references and caches MM once per container so we do not depend
>> on @current pointing to a valid task descriptor anymore.
>>
>> This is needed by the following patch to do proper cleanup in time.
>> This depends on "powerpc/powernv/ioda: Fix endianness when reading TCEs"
>> to do proper cleanup via tce_iommu_clear() patch.
>>
>> To keep API consistent, this replaces mm_context_t with mm_struct;
>> we stick to mm_struct as mm_iommu_adjust_locked_vm() helper needs
>> access to &mm->mmap_sem.
>>
>> This should cause no behavioral change.
>>
>> Signed-off-by: Alexey Kardashevskiy <a...@ozlabs.ru>
>> Reviewed-by: Nicholas Piggin <npig...@gmail.com>
>> Acked-by: Balbir Singh <bsinghar...@gmail.com>
>> ---
>> Changes:
>> v2:
>> * added BUG_ON(container->mm && (container->mm != current->mm)) in
>> tce_iommu_register_pages()
>> * added note about containers referencing MM
>> ---
>> arch/powerpc/include/asm/mmu_context.h | 20 +++++++------
>> arch/powerpc/kernel/setup-common.c | 2 +-
>> arch/powerpc/mm/mmu_context_book3s64.c | 4 +--
>> arch/powerpc/mm/mmu_context_iommu.c | 55
>> ++++++++++++++--------------------
>> drivers/vfio/vfio_iommu_spapr_tce.c | 41 ++++++++++++++++---------
>> 5 files changed, 63 insertions(+), 59 deletions(-)
>>
>> diff --git a/arch/powerpc/include/asm/mmu_context.h
>> b/arch/powerpc/include/asm/mmu_context.h
>> index 5c45114..b9e3f0a 100644
>> --- a/arch/powerpc/include/asm/mmu_context.h
>> +++ b/arch/powerpc/include/asm/mmu_context.h
>> @@ -19,16 +19,18 @@ extern void destroy_context(struct mm_struct *mm);
>> struct mm_iommu_table_group_mem_t;
>>
>> extern int isolate_lru_page(struct page *page); /* from internal.h */
>> -extern bool mm_iommu_preregistered(void);
>> -extern long mm_iommu_get(unsigned long ua, unsigned long entries,
>> +extern bool mm_iommu_preregistered(struct mm_struct *mm);
>> +extern long mm_iommu_get(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_iommu_table_group_mem_t *mem);
>> -extern void mm_iommu_init(mm_context_t *ctx);
>> -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 struct mm_iommu_table_group_mem_t *mm_iommu_find(unsigned long ua,
>> - unsigned long entries);
>> +extern long mm_iommu_put(struct mm_struct *mm,
>> + struct mm_iommu_table_group_mem_t *mem);
>> +extern void mm_iommu_init(struct mm_struct *mm);
>> +extern void mm_iommu_cleanup(struct mm_struct *mm);
>> +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_find(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 long *hpa);
>> extern long mm_iommu_mapped_inc(struct mm_iommu_table_group_mem_t *mem);
>> diff --git a/arch/powerpc/kernel/setup-common.c
>> b/arch/powerpc/kernel/setup-common.c
>> index dba265c..942cf49 100644
>> --- a/arch/powerpc/kernel/setup-common.c
>> +++ b/arch/powerpc/kernel/setup-common.c
>> @@ -906,7 +906,7 @@ void __init setup_arch(char **cmdline_p)
>> init_mm.context.pte_frag = NULL;
>> #endif
>> #ifdef CONFIG_SPAPR_TCE_IOMMU
>> - mm_iommu_init(&init_mm.context);
>> + mm_iommu_init(&init_mm);
>> #endif
>> irqstack_early_init();
>> exc_lvl_early_init();
>> diff --git a/arch/powerpc/mm/mmu_context_book3s64.c
>> b/arch/powerpc/mm/mmu_context_book3s64.c
>> index b114f8b..ad82735 100644
>> --- a/arch/powerpc/mm/mmu_context_book3s64.c
>> +++ b/arch/powerpc/mm/mmu_context_book3s64.c
>> @@ -115,7 +115,7 @@ int init_new_context(struct task_struct *tsk, struct
>> mm_struct *mm)
>> mm->context.pte_frag = NULL;
>> #endif
>> #ifdef CONFIG_SPAPR_TCE_IOMMU
>> - mm_iommu_init(&mm->context);
>> + mm_iommu_init(mm);
>> #endif
>> return 0;
>> }
>> @@ -160,7 +160,7 @@ 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);
>> + mm_iommu_cleanup(mm);
>> #endif
>>
>> #ifdef CONFIG_PPC_ICSWX
>> diff --git a/arch/powerpc/mm/mmu_context_iommu.c
>> b/arch/powerpc/mm/mmu_context_iommu.c
>> index e0f1c33..4c6db09 100644
>> --- a/arch/powerpc/mm/mmu_context_iommu.c
>> +++ b/arch/powerpc/mm/mmu_context_iommu.c
>> @@ -56,7 +56,7 @@ static long mm_iommu_adjust_locked_vm(struct mm_struct *mm,
>> }
>>
>> pr_debug("[%d] RLIMIT_MEMLOCK HASH64 %c%ld %ld/%ld\n",
>> - current->pid,
>> + current ? current->pid : 0,
>> incr ? '+' : '-',
>> npages << PAGE_SHIFT,
>> mm->locked_vm << PAGE_SHIFT,
>> @@ -66,12 +66,9 @@ static long mm_iommu_adjust_locked_vm(struct mm_struct
>> *mm,
>> return ret;
>> }
>>
>> -bool mm_iommu_preregistered(void)
>> +bool mm_iommu_preregistered(struct mm_struct *mm)
>> {
>> - if (!current || !current->mm)
>> - return false;
>> -
>> - return !list_empty(¤t->mm->context.iommu_group_mem_list);
>> + return !list_empty(&mm->context.iommu_group_mem_list);
>> }
>> EXPORT_SYMBOL_GPL(mm_iommu_preregistered);
>>
>> @@ -124,19 +121,16 @@ static int mm_iommu_move_page_from_cma(struct page
>> *page)
>> return 0;
>> }
>>
>> -long mm_iommu_get(unsigned long ua, unsigned long entries,
>> +long mm_iommu_get(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;
>> long i, j, ret = 0, locked_entries = 0;
>> struct page *page = NULL;
>>
>> - if (!current || !current->mm)
>> - return -ESRCH; /* process exited */
>> -
>> mutex_lock(&mem_list_mutex);
>>
>> - list_for_each_entry_rcu(mem, ¤t->mm->context.iommu_group_mem_list,
>> + list_for_each_entry_rcu(mem, &mm->context.iommu_group_mem_list,
>> next) {
>> if ((mem->ua == ua) && (mem->entries == entries)) {
>> ++mem->used;
>> @@ -154,7 +148,7 @@ long mm_iommu_get(unsigned long ua, unsigned long
>> entries,
>>
>> }
>>
>> - ret = mm_iommu_adjust_locked_vm(current->mm, entries, true);
>> + ret = mm_iommu_adjust_locked_vm(mm, entries, true);
>> if (ret)
>> goto unlock_exit;
>>
>> @@ -215,11 +209,11 @@ long mm_iommu_get(unsigned long ua, unsigned long
>> entries,
>> mem->entries = entries;
>> *pmem = mem;
>>
>> - list_add_rcu(&mem->next, ¤t->mm->context.iommu_group_mem_list);
>> + list_add_rcu(&mem->next, &mm->context.iommu_group_mem_list);
>>
>> unlock_exit:
>> if (locked_entries && ret)
>> - mm_iommu_adjust_locked_vm(current->mm, locked_entries, false);
>> + mm_iommu_adjust_locked_vm(mm, locked_entries, false);
>>
>> mutex_unlock(&mem_list_mutex);
>>
>> @@ -264,17 +258,13 @@ static void mm_iommu_free(struct rcu_head *head)
>> static void mm_iommu_release(struct mm_iommu_table_group_mem_t *mem)
>> {
>> list_del_rcu(&mem->next);
>> - mm_iommu_adjust_locked_vm(current->mm, mem->entries, false);
>> call_rcu(&mem->rcu, mm_iommu_free);
>> }
>>
>> -long mm_iommu_put(struct mm_iommu_table_group_mem_t *mem)
>> +long mm_iommu_put(struct mm_struct *mm, struct mm_iommu_table_group_mem_t
>> *mem)
>> {
>> long ret = 0;
>>
>> - if (!current || !current->mm)
>> - return -ESRCH; /* process exited */
>> -
>> mutex_lock(&mem_list_mutex);
>>
>> if (mem->used == 0) {
>> @@ -297,6 +287,8 @@ long mm_iommu_put(struct mm_iommu_table_group_mem_t *mem)
>> /* @mapped became 0 so now mappings are disabled, release the region */
>> mm_iommu_release(mem);
>>
>> + mm_iommu_adjust_locked_vm(mm, mem->entries, false);
>> +
>> unlock_exit:
>> mutex_unlock(&mem_list_mutex);
>>
>> @@ -304,14 +296,12 @@ long mm_iommu_put(struct mm_iommu_table_group_mem_t
>> *mem)
>> }
>> EXPORT_SYMBOL_GPL(mm_iommu_put);
>>
>> -struct mm_iommu_table_group_mem_t *mm_iommu_lookup(unsigned long ua,
>> - unsigned long size)
>> +struct mm_iommu_table_group_mem_t *mm_iommu_lookup(struct mm_struct *mm,
>> + unsigned long ua, unsigned long size)
>> {
>> struct mm_iommu_table_group_mem_t *mem, *ret = NULL;
>>
>> - list_for_each_entry_rcu(mem,
>> - ¤t->mm->context.iommu_group_mem_list,
>> - next) {
>> + list_for_each_entry_rcu(mem, &mm->context.iommu_group_mem_list, next) {
>> if ((mem->ua <= ua) &&
>> (ua + size <= mem->ua +
>> (mem->entries << PAGE_SHIFT))) {
>> @@ -324,14 +314,12 @@ struct mm_iommu_table_group_mem_t
>> *mm_iommu_lookup(unsigned long ua,
>> }
>> EXPORT_SYMBOL_GPL(mm_iommu_lookup);
>>
>> -struct mm_iommu_table_group_mem_t *mm_iommu_find(unsigned long ua,
>> - unsigned long entries)
>> +struct mm_iommu_table_group_mem_t *mm_iommu_find(struct mm_struct *mm,
>> + unsigned long ua, unsigned long entries)
>> {
>> struct mm_iommu_table_group_mem_t *mem, *ret = NULL;
>>
>> - list_for_each_entry_rcu(mem,
>> - ¤t->mm->context.iommu_group_mem_list,
>> - next) {
>> + list_for_each_entry_rcu(mem, &mm->context.iommu_group_mem_list, next) {
>> if ((mem->ua == ua) && (mem->entries == entries)) {
>> ret = mem;
>> break;
>> @@ -373,16 +361,17 @@ void mm_iommu_mapped_dec(struct
>> mm_iommu_table_group_mem_t *mem)
>> }
>> EXPORT_SYMBOL_GPL(mm_iommu_mapped_dec);
>>
>> -void mm_iommu_init(mm_context_t *ctx)
>> +void mm_iommu_init(struct mm_struct *mm)
>> {
>> - INIT_LIST_HEAD_RCU(&ctx->iommu_group_mem_list);
>> + INIT_LIST_HEAD_RCU(&mm->context.iommu_group_mem_list);
>> }
>>
>> -void mm_iommu_cleanup(mm_context_t *ctx)
>> +void mm_iommu_cleanup(struct mm_struct *mm)
>> {
>> struct mm_iommu_table_group_mem_t *mem, *tmp;
>>
>> - list_for_each_entry_safe(mem, tmp, &ctx->iommu_group_mem_list, next) {
>> + list_for_each_entry_safe(mem, tmp, &mm->context.iommu_group_mem_list,
>> + next) {
>> list_del_rcu(&mem->next);
>> mm_iommu_do_free(mem);
>> }
>> diff --git a/drivers/vfio/vfio_iommu_spapr_tce.c
>> b/drivers/vfio/vfio_iommu_spapr_tce.c
>> index 80378dd..3d2a65c 100644
>> --- a/drivers/vfio/vfio_iommu_spapr_tce.c
>> +++ b/drivers/vfio/vfio_iommu_spapr_tce.c
>> @@ -98,6 +98,7 @@ struct tce_container {
>> bool enabled;
>> bool v2;
>> unsigned long locked_pages;
>> + struct mm_struct *mm;
>> struct iommu_table *tables[IOMMU_TABLE_GROUP_MAX_TABLES];
>> struct list_head group_list;
>> };
>> @@ -110,11 +111,11 @@ static long tce_iommu_unregister_pages(struct
>> tce_container *container,
>> if ((vaddr & ~PAGE_MASK) || (size & ~PAGE_MASK))
>> return -EINVAL;
>>
>> - mem = mm_iommu_find(vaddr, size >> PAGE_SHIFT);
>> + mem = mm_iommu_find(container->mm, vaddr, size >> PAGE_SHIFT);
>> if (!mem)
>> return -ENOENT;
>>
>> - return mm_iommu_put(mem);
>> + return mm_iommu_put(container->mm, mem);
>> }
>>
>> static long tce_iommu_register_pages(struct tce_container *container,
>> @@ -128,7 +129,16 @@ static long tce_iommu_register_pages(struct
>> tce_container *container,
>> ((vaddr + size) < vaddr))
>> return -EINVAL;
>>
>> - ret = mm_iommu_get(vaddr, entries, &mem);
>> + if (!container->mm) {
>> + if (!current->mm)
>> + return -ESRCH; /* process exited */
>
> You're only verifying current->mm if container->mm is not set. If
> container->mm has been populated, then the process exits, previously
> the mm_iommu_get() would have silently failed. Now, you will register
> pages against the stale mm.
>
> I don't see anything obvious bad that would happen because of that,
> but is it what you intended?Yes, I want to keep things simple unless they can hurt. >> + atomic_inc(¤t->mm->mm_count); >> + BUG_ON(container->mm && (container->mm != current->mm)); > > What prevents the container fd being passed to another process (via > fork() or a unix domain socket)? Without that, this allows the user > to BUG() the system. This exact BUG_ON is wrong actually - "if (!container->mm)" means that BUG_ON will not ever happen. So. I need a piece of advise what check would make sense here. I'd just remove BUG_ON and that's it... -- Alexey
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