KVM: s390: allow sie enablement for multi-threaded programs

Improve the code to upgrade the standard 2K page tables to 4K page tables
with PGSTEs to allow the operation to happen when the program is already
multi-threaded.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 117 insertions, 64 deletions

diff --git a/arch/s390/mm/pgtable.c b/arch/s390/mm/pgtable.c
index a8154a1a2c94..6d332487f363 100644
--- a/arch/s390/mm/pgtable.c
+++ b/arch/s390/mm/pgtable.c
@@ -731,6 +731,11 @@ void gmap_do_ipte_notify(struct mm_struct *mm, unsigned long addr, pte_t *pte)
         spin_unlock(&gmap_notifier_lock);
 }
 
+static inline int page_table_with_pgste(struct page *page)
+{
+        return atomic_read(&page->_mapcount) == 0;
+}
+
 static inline unsigned long *page_table_alloc_pgste(struct mm_struct *mm,
                                                     unsigned long vmaddr)
 {
@@ -750,7 +755,7 @@ static inline unsigned long *page_table_alloc_pgste(struct mm_struct *mm,
         mp->vmaddr = vmaddr & PMD_MASK;
         INIT_LIST_HEAD(&mp->mapper);
         page->index = (unsigned long) mp;
-        atomic_set(&page->_mapcount, 3);
+        atomic_set(&page->_mapcount, 0);
         table = (unsigned long *) page_to_phys(page);
         clear_table(table, _PAGE_TYPE_EMPTY, PAGE_SIZE/2);
         clear_table(table + PTRS_PER_PTE, 0, PAGE_SIZE/2);
@@ -821,6 +826,11 @@ EXPORT_SYMBOL(set_guest_storage_key);
 
 #else /* CONFIG_PGSTE */
 
+static inline int page_table_with_pgste(struct page *page)
+{
+        return 0;
+}
+
 static inline unsigned long *page_table_alloc_pgste(struct mm_struct *mm,
                                                     unsigned long vmaddr)
 {
@@ -897,12 +907,12 @@ void page_table_free(struct mm_struct *mm, unsigned long *table)
         struct page *page;
         unsigned int bit, mask;
 
-        if (mm_has_pgste(mm)) {
+        page = pfn_to_page(__pa(table) >> PAGE_SHIFT);
+        if (page_table_with_pgste(page)) {
                 gmap_disconnect_pgtable(mm, table);
                 return page_table_free_pgste(table);
         }
         /* Free 1K/2K page table fragment of a 4K page */
-        page = pfn_to_page(__pa(table) >> PAGE_SHIFT);
         bit = 1 << ((__pa(table) & ~PAGE_MASK)/(PTRS_PER_PTE*sizeof(pte_t)));
         spin_lock_bh(&mm->context.list_lock);
         if ((atomic_read(&page->_mapcount) & FRAG_MASK) != FRAG_MASK)
@@ -940,14 +950,14 @@ void page_table_free_rcu(struct mmu_gather *tlb, unsigned long *table)
         unsigned int bit, mask;
 
         mm = tlb->mm;
-        if (mm_has_pgste(mm)) {
+        page = pfn_to_page(__pa(table) >> PAGE_SHIFT);
+        if (page_table_with_pgste(page)) {
                 gmap_disconnect_pgtable(mm, table);
                 table = (unsigned long *) (__pa(table) | FRAG_MASK);
                 tlb_remove_table(tlb, table);
                 return;
         }
         bit = 1 << ((__pa(table) & ~PAGE_MASK) / (PTRS_PER_PTE*sizeof(pte_t)));
-        page = pfn_to_page(__pa(table) >> PAGE_SHIFT);
         spin_lock_bh(&mm->context.list_lock);
         if ((atomic_read(&page->_mapcount) & FRAG_MASK) != FRAG_MASK)
                 list_del(&page->lru);
@@ -1033,36 +1043,120 @@ void tlb_remove_table(struct mmu_gather *tlb, void *table)
 }
 
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
-void thp_split_vma(struct vm_area_struct *vma)
+static inline void thp_split_vma(struct vm_area_struct *vma)
 {
         unsigned long addr;
-        struct page *page;
 
-        for (addr = vma->vm_start; addr < vma->vm_end; addr += PAGE_SIZE) {
-                page = follow_page(vma, addr, FOLL_SPLIT);
-        }
+        for (addr = vma->vm_start; addr < vma->vm_end; addr += PAGE_SIZE)
+                follow_page(vma, addr, FOLL_SPLIT);
 }
 
-void thp_split_mm(struct mm_struct *mm)
+static inline void thp_split_mm(struct mm_struct *mm)
 {
-        struct vm_area_struct *vma = mm->mmap;
+        struct vm_area_struct *vma;
 
-        while (vma != NULL) {
+        for (vma = mm->mmap; vma != NULL; vma = vma->vm_next) {
                 thp_split_vma(vma);
                 vma->vm_flags &= ~VM_HUGEPAGE;
                 vma->vm_flags |= VM_NOHUGEPAGE;
-                vma = vma->vm_next;
         }
+        mm->def_flags |= VM_NOHUGEPAGE;
+}
+#else
+static inline void thp_split_mm(struct mm_struct *mm)
+{
 }
 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
 
+static unsigned long page_table_realloc_pmd(struct mmu_gather *tlb,
+                                struct mm_struct *mm, pud_t *pud,
+                                unsigned long addr, unsigned long end)
+{
+        unsigned long next, *table, *new;
+        struct page *page;
+        pmd_t *pmd;
+
+        pmd = pmd_offset(pud, addr);
+        do {
+                next = pmd_addr_end(addr, end);
+again:
+                if (pmd_none_or_clear_bad(pmd))
+                        continue;
+                table = (unsigned long *) pmd_deref(*pmd);
+                page = pfn_to_page(__pa(table) >> PAGE_SHIFT);
+                if (page_table_with_pgste(page))
+                        continue;
+                /* Allocate new page table with pgstes */
+                new = page_table_alloc_pgste(mm, addr);
+                if (!new) {
+                        mm->context.has_pgste = 0;
+                        continue;
+                }
+                spin_lock(&mm->page_table_lock);
+                if (likely((unsigned long *) pmd_deref(*pmd) == table)) {
+                        /* Nuke pmd entry pointing to the "short" page table */
+                        pmdp_flush_lazy(mm, addr, pmd);
+                        pmd_clear(pmd);
+                        /* Copy ptes from old table to new table */
+                        memcpy(new, table, PAGE_SIZE/2);
+                        clear_table(table, _PAGE_INVALID, PAGE_SIZE/2);
+                        /* Establish new table */
+                        pmd_populate(mm, pmd, (pte_t *) new);
+                        /* Free old table with rcu, there might be a walker! */
+                        page_table_free_rcu(tlb, table);
+                        new = NULL;
+                }
+                spin_unlock(&mm->page_table_lock);
+                if (new) {
+                        page_table_free_pgste(new);
+                        goto again;
+                }
+        } while (pmd++, addr = next, addr != end);
+
+        return addr;
+}
+
+static unsigned long page_table_realloc_pud(struct mmu_gather *tlb,
+                                   struct mm_struct *mm, pgd_t *pgd,
+                                   unsigned long addr, unsigned long end)
+{
+        unsigned long next;
+        pud_t *pud;
+
+        pud = pud_offset(pgd, addr);
+        do {
+                next = pud_addr_end(addr, end);
+                if (pud_none_or_clear_bad(pud))
+                        continue;
+                next = page_table_realloc_pmd(tlb, mm, pud, addr, next);
+        } while (pud++, addr = next, addr != end);
+
+        return addr;
+}
+
+static void page_table_realloc(struct mmu_gather *tlb, struct mm_struct *mm,
+                               unsigned long addr, unsigned long end)
+{
+        unsigned long next;
+        pgd_t *pgd;
+
+        pgd = pgd_offset(mm, addr);
+        do {
+                next = pgd_addr_end(addr, end);
+                if (pgd_none_or_clear_bad(pgd))
+                        continue;
+                next = page_table_realloc_pud(tlb, mm, pgd, addr, next);
+        } while (pgd++, addr = next, addr != end);
+}
+
 /*
  * switch on pgstes for its userspace process (for kvm)
  */
 int s390_enable_sie(void)
 {
         struct task_struct *tsk = current;
-        struct mm_struct *mm, *old_mm;
+        struct mm_struct *mm = tsk->mm;
+        struct mmu_gather tlb;
 
         /* Do we have switched amode? If no, we cannot do sie */
         if (s390_user_mode == HOME_SPACE_MODE)
@@ -1072,57 +1166,16 @@ int s390_enable_sie(void)
         if (mm_has_pgste(tsk->mm))
                 return 0;
 
-        /* lets check if we are allowed to replace the mm */
-        task_lock(tsk);
-        if (!tsk->mm || atomic_read(&tsk->mm->mm_users) > 1 ||
-#ifdef CONFIG_AIO
-            !hlist_empty(&tsk->mm->ioctx_list) ||
-#endif
-            tsk->mm != tsk->active_mm) {
-                task_unlock(tsk);
-                return -EINVAL;
-        }
-        task_unlock(tsk);
-
-        /* we copy the mm and let dup_mm create the page tables with_pgstes */
-        tsk->mm->context.alloc_pgste = 1;
-        /* make sure that both mms have a correct rss state */
-        sync_mm_rss(tsk->mm);
-        mm = dup_mm(tsk);
-        tsk->mm->context.alloc_pgste = 0;
-        if (!mm)
-                return -ENOMEM;
-
-#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+        down_write(&mm->mmap_sem);
         /* split thp mappings and disable thp for future mappings */
         thp_split_mm(mm);
-        mm->def_flags |= VM_NOHUGEPAGE;
-#endif
-
-        /* Now lets check again if something happened */
-        task_lock(tsk);
-        if (!tsk->mm || atomic_read(&tsk->mm->mm_users) > 1 ||
-#ifdef CONFIG_AIO
-            !hlist_empty(&tsk->mm->ioctx_list) ||
-#endif
-            tsk->mm != tsk->active_mm) {
-                mmput(mm);
-                task_unlock(tsk);
-                return -EINVAL;
-        }
-
-        /* ok, we are alone. No ptrace, no threads, etc. */
-        old_mm = tsk->mm;
-        tsk->mm = tsk->active_mm = mm;
-        preempt_disable();
-        update_mm(mm, tsk);
-        atomic_inc(&mm->context.attach_count);
-        atomic_dec(&old_mm->context.attach_count);
-        cpumask_set_cpu(smp_processor_id(), mm_cpumask(mm));
-        preempt_enable();
-        task_unlock(tsk);
-        mmput(old_mm);
-        return 0;
+        /* Reallocate the page tables with pgstes */
+        mm->context.has_pgste = 1;
+        tlb_gather_mmu(&tlb, mm, 0);
+        page_table_realloc(&tlb, mm, 0, TASK_SIZE);
+        tlb_finish_mmu(&tlb, 0, -1);
+        up_write(&mm->mmap_sem);
+        return mm->context.has_pgste ? 0 : -ENOMEM;
 }
 EXPORT_SYMBOL_GPL(s390_enable_sie);