[PATCH kernel 05/15] powerpc/iommu: Stop using @current in mm_iommu_xxx
David Gibson
david at gibson.dropbear.id.au
Fri Aug 12 12:57:24 AEST 2016
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 <aik at 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?
> 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().
> +
> + atomic_inc(¤t->mm->mm_count);
What balances this atomic_inc()? Is it the mmdrop() added to
tce_iommu_release()?
> + 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.
> +
> + 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;
>
--
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
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