On 12/08/16 12:57, David Gibson wrote:
> On Wed, Aug 03, 2016 at 06:40:46PM +1000, 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 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>
>> ---
>> 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 | 54
>> ++++++++++++++--------------------
>> drivers/vfio/vfio_iommu_spapr_tce.c | 41 ++++++++++++++++----------
>> 5 files changed, 62 insertions(+), 59 deletions(-)
>>
>> diff --git a/arch/powerpc/include/asm/mmu_context.h
>> b/arch/powerpc/include/asm/mmu_context.h
>> index 9d2cd0c..b85cc7b 100644
>> --- a/arch/powerpc/include/asm/mmu_context.h
>> +++ b/arch/powerpc/include/asm/mmu_context.h
>> @@ -18,16 +18,18 @@ 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_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 714b4ba..e90b68a 100644
>> --- a/arch/powerpc/kernel/setup-common.c
>> +++ b/arch/powerpc/kernel/setup-common.c
>> @@ -905,7 +905,7 @@ 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 da6a216..ee6685b 100644
>> --- a/arch/powerpc/mm/mmu_context_iommu.c
>> +++ b/arch/powerpc/mm/mmu_context_iommu.c
>> @@ -53,7 +53,7 @@ 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,
>> @@ -63,28 +63,22 @@ 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);
>>
>> -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;
>> @@ -102,7 +96,7 @@ 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;
>>
>> @@ -142,11 +136,11 @@ 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);
>>
>> @@ -191,16 +185,13 @@ 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);
>
> AFAICT, you've moved this call from _release() to _put(). Won't that cause a
> behavioural change?
mm_iommu_put() calls mm_iommu_adjust_locked_vm() right after
m_iommu_release() so no, it does not look so.
>> 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);
>>
>> @@ -224,6 +215,8 @@ 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);
>>
>> @@ -231,14 +224,12 @@ unlock_exit:
>> }
>> 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))) {
>> @@ -251,14 +242,12 @@ 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;
>> @@ -300,16 +289,17 @@ 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..9752e77 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,
>> @@ -128,10 +129,17 @@ static long tce_iommu_register_pages(struct
>> tce_container *container,
>> ((vaddr + size) < vaddr))
>> return -EINVAL;
>>
>> - r<et = mm_iommu_get(vaddr, entries, &mem);
>> + if (!container->mm) {
>> + if (!current->mm)
>> + return -ESRCH; /* process exited */
>
> Can this ever happen? Surely the ioctl() path shouldn't be called
> after the process mm has been cleaned up? i.e. should this be a
> WARN_ON().
Not sure with SMP (one thread doing ioctl(), another - exiting QEMU) if it
is not that impossible but it is quite hard to trigger this check.
>
>> +
>> + atomic_inc(¤t->mm->mm_count);
>
> What balances this atomic_inc()? Is it the mmdrop() added to
> tce_iommu_release()?
Yes. Surprisingly there is no mmget(), there is mmget_not_zero() but it is
for mm->mm_users.
>
>> + container->mm = current->mm;
>> + }
>
> Surely you need an error (or else a BUG_ON()) if current->mm !=
> container->mm != NULL. I believe VFIO already assumes the container
> is owned only by a single mm, but it looks like you should verify that here.
I am not sure I really want to enforce it, do I? Who knows what kind of a
crazy person would create a container, pin pages and fork() that userspace
tool which may not be QEMU but something custom using DPDK or something.
What harm can not having this BUG_ON() cause?
>
>> +
>> + ret = mm_iommu_get(container->mm, vaddr, entries, &mem);
>> if (ret)
>> return ret;
>> -
>> container->enabled = true;
>>
>> return 0;
>> @@ -354,6 +362,8 @@ static void tce_iommu_release(void *iommu_data)
>> tce_iommu_free_table(tbl);
>> }
>>
>> + if (container->mm)
>> + mmdrop(container->mm);
>> tce_iommu_disable(container);
>> mutex_destroy(&container->lock);
>>
>> @@ -369,13 +379,14 @@ static void tce_iommu_unuse_page(struct tce_container
>> *container,
>> put_page(page);
>> }
>>
>> -static int tce_iommu_prereg_ua_to_hpa(unsigned long tce, unsigned long size,
>> +static int tce_iommu_prereg_ua_to_hpa(struct tce_container *container,
>> + unsigned long tce, unsigned long size,
>> unsigned long *phpa, struct mm_iommu_table_group_mem_t **pmem)
>> {
>> long ret = 0;
>> struct mm_iommu_table_group_mem_t *mem;
>>
>> - mem = mm_iommu_lookup(tce, size);
>> + mem = mm_iommu_lookup(container->mm, tce, size);
>> if (!mem)
>> return -EINVAL;
>>
>> @@ -388,18 +399,18 @@ static int tce_iommu_prereg_ua_to_hpa(unsigned long
>> tce, unsigned long size,
>> return 0;
>> }
>>
>> -static void tce_iommu_unuse_page_v2(struct iommu_table *tbl,
>> - unsigned long entry)
>> +static void tce_iommu_unuse_page_v2(struct tce_container *container,
>> + struct iommu_table *tbl, unsigned long entry)
>> {
>> struct mm_iommu_table_group_mem_t *mem = NULL;
>> int ret;
>> unsigned long hpa = 0;
>> unsigned long *pua = IOMMU_TABLE_USERSPACE_ENTRY(tbl, entry);
>>
>> - if (!pua || !current || !current->mm)
>> + if (!pua)
>> return;
>>
>> - ret = tce_iommu_prereg_ua_to_hpa(*pua, IOMMU_PAGE_SIZE(tbl),
>> + ret = tce_iommu_prereg_ua_to_hpa(container, *pua, IOMMU_PAGE_SIZE(tbl),
>> &hpa, &mem);
>> if (ret)
>> pr_debug("%s: tce %lx at #%lx was not cached, ret=%d\n",
>> @@ -429,7 +440,7 @@ static int tce_iommu_clear(struct tce_container
>> *container,
>> continue;
>>
>> if (container->v2) {
>> - tce_iommu_unuse_page_v2(tbl, entry);
>> + tce_iommu_unuse_page_v2(container, tbl, entry);
>> continue;
>> }
>>
>> @@ -514,8 +525,8 @@ static long tce_iommu_build_v2(struct tce_container
>> *container,
>> unsigned long *pua = IOMMU_TABLE_USERSPACE_ENTRY(tbl,
>> entry + i);
>>
>> - ret = tce_iommu_prereg_ua_to_hpa(tce, IOMMU_PAGE_SIZE(tbl),
>> - &hpa, &mem);
>> + ret = tce_iommu_prereg_ua_to_hpa(container,
>> + tce, IOMMU_PAGE_SIZE(tbl), &hpa, &mem);
>> if (ret)
>> break;
>>
>> @@ -536,7 +547,7 @@ static long tce_iommu_build_v2(struct tce_container
>> *container,
>> ret = iommu_tce_xchg(tbl, entry + i, &hpa, &dirtmp);
>> if (ret) {
>> /* dirtmp cannot be DMA_NONE here */
>> - tce_iommu_unuse_page_v2(tbl, entry + i);
>> + tce_iommu_unuse_page_v2(container, tbl, entry + i);
>> pr_err("iommu_tce: %s failed ioba=%lx, tce=%lx,
>> ret=%ld\n",
>> __func__, entry << tbl->it_page_shift,
>> tce, ret);
>> @@ -544,7 +555,7 @@ static long tce_iommu_build_v2(struct tce_container
>> *container,
>> }
>>
>> if (dirtmp != DMA_NONE)
>> - tce_iommu_unuse_page_v2(tbl, entry + i);
>> + tce_iommu_unuse_page_v2(container, tbl, entry + i);
>>
>> *pua = tce;
>>
>
--
Alexey
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