s390: KVM preparation: provide hook to enable pgstes in user pagetable
The SIE instruction on s390 uses the 2nd half of the page table page to virtualize the storage keys of a guest. This patch offers the s390_enable_sie function, which reorganizes the page tables of a single-threaded process to reserve space in the page table: s390_enable_sie makes sure that the process is single threaded and then uses dup_mm to create a new mm with reorganized page tables. The old mm is freed and the process has now a page status extended field after every page table. Code that wants to exploit pgstes should SELECT CONFIG_PGSTE. This patch has a small common code hit, namely making dup_mm non-static. Edit (Carsten): I've modified Martin's patch, following Jeremy Fitzhardinge's review feedback. Now we do have the prototype for dup_mm in include/linux/sched.h. Following Martin's suggestion, s390_enable_sie() does now call task_lock() to prevent race against ptrace modification of mm_users. Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com> Signed-off-by: Carsten Otte <cotte@de.ibm.com> Acked-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Avi Kivity <avi@qumranet.com>
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Родитель
37817f2982
Коммит
402b08622d
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@ -62,6 +62,10 @@ config GENERIC_LOCKBREAK
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default y
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depends on SMP && PREEMPT
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config PGSTE
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bool
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default y if KVM
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mainmenu "Linux Kernel Configuration"
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config S390
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@ -316,7 +316,11 @@ static int __init early_parse_ipldelay(char *p)
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early_param("ipldelay", early_parse_ipldelay);
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#ifdef CONFIG_S390_SWITCH_AMODE
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#ifdef CONFIG_PGSTE
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unsigned int switch_amode = 1;
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#else
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unsigned int switch_amode = 0;
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#endif
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EXPORT_SYMBOL_GPL(switch_amode);
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static void set_amode_and_uaccess(unsigned long user_amode,
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@ -30,11 +30,27 @@
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#define TABLES_PER_PAGE 4
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#define FRAG_MASK 15UL
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#define SECOND_HALVES 10UL
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void clear_table_pgstes(unsigned long *table)
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{
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clear_table(table, _PAGE_TYPE_EMPTY, PAGE_SIZE/4);
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memset(table + 256, 0, PAGE_SIZE/4);
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clear_table(table + 512, _PAGE_TYPE_EMPTY, PAGE_SIZE/4);
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memset(table + 768, 0, PAGE_SIZE/4);
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}
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#else
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#define ALLOC_ORDER 2
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#define TABLES_PER_PAGE 2
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#define FRAG_MASK 3UL
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#define SECOND_HALVES 2UL
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void clear_table_pgstes(unsigned long *table)
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{
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clear_table(table, _PAGE_TYPE_EMPTY, PAGE_SIZE/2);
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memset(table + 256, 0, PAGE_SIZE/2);
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}
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#endif
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unsigned long *crst_table_alloc(struct mm_struct *mm, int noexec)
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@ -153,7 +169,7 @@ unsigned long *page_table_alloc(struct mm_struct *mm)
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unsigned long *table;
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unsigned long bits;
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bits = mm->context.noexec ? 3UL : 1UL;
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bits = (mm->context.noexec || mm->context.pgstes) ? 3UL : 1UL;
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spin_lock(&mm->page_table_lock);
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page = NULL;
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if (!list_empty(&mm->context.pgtable_list)) {
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@ -170,7 +186,10 @@ unsigned long *page_table_alloc(struct mm_struct *mm)
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pgtable_page_ctor(page);
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page->flags &= ~FRAG_MASK;
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table = (unsigned long *) page_to_phys(page);
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clear_table(table, _PAGE_TYPE_EMPTY, PAGE_SIZE);
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if (mm->context.pgstes)
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clear_table_pgstes(table);
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else
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clear_table(table, _PAGE_TYPE_EMPTY, PAGE_SIZE);
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spin_lock(&mm->page_table_lock);
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list_add(&page->lru, &mm->context.pgtable_list);
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}
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@ -191,7 +210,7 @@ void page_table_free(struct mm_struct *mm, unsigned long *table)
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struct page *page;
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unsigned long bits;
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bits = mm->context.noexec ? 3UL : 1UL;
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bits = (mm->context.noexec || mm->context.pgstes) ? 3UL : 1UL;
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bits <<= (__pa(table) & (PAGE_SIZE - 1)) / 256 / sizeof(unsigned long);
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page = pfn_to_page(__pa(table) >> PAGE_SHIFT);
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spin_lock(&mm->page_table_lock);
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@ -228,3 +247,43 @@ void disable_noexec(struct mm_struct *mm, struct task_struct *tsk)
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mm->context.noexec = 0;
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update_mm(mm, tsk);
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}
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/*
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* switch on pgstes for its userspace process (for kvm)
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*/
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int s390_enable_sie(void)
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{
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struct task_struct *tsk = current;
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struct mm_struct *mm;
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int rc;
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task_lock(tsk);
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rc = 0;
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if (tsk->mm->context.pgstes)
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goto unlock;
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rc = -EINVAL;
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if (!tsk->mm || atomic_read(&tsk->mm->mm_users) > 1 ||
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tsk->mm != tsk->active_mm || tsk->mm->ioctx_list)
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goto unlock;
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tsk->mm->context.pgstes = 1; /* dirty little tricks .. */
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mm = dup_mm(tsk);
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tsk->mm->context.pgstes = 0;
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rc = -ENOMEM;
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if (!mm)
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goto unlock;
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mmput(tsk->mm);
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tsk->mm = tsk->active_mm = mm;
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preempt_disable();
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update_mm(mm, tsk);
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cpu_set(smp_processor_id(), mm->cpu_vm_mask);
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preempt_enable();
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rc = 0;
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unlock:
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task_unlock(tsk);
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return rc;
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}
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EXPORT_SYMBOL_GPL(s390_enable_sie);
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@ -7,6 +7,7 @@ typedef struct {
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unsigned long asce_bits;
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unsigned long asce_limit;
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int noexec;
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int pgstes;
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} mm_context_t;
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#endif
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@ -20,7 +20,13 @@ static inline int init_new_context(struct task_struct *tsk,
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#ifdef CONFIG_64BIT
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mm->context.asce_bits |= _ASCE_TYPE_REGION3;
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#endif
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mm->context.noexec = s390_noexec;
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if (current->mm->context.pgstes) {
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mm->context.noexec = 0;
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mm->context.pgstes = 1;
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} else {
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mm->context.noexec = s390_noexec;
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mm->context.pgstes = 0;
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}
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mm->context.asce_limit = STACK_TOP_MAX;
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crst_table_init((unsigned long *) mm->pgd, pgd_entry_type(mm));
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return 0;
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@ -966,6 +966,7 @@ static inline pte_t mk_swap_pte(unsigned long type, unsigned long offset)
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extern int add_shared_memory(unsigned long start, unsigned long size);
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extern int remove_shared_memory(unsigned long start, unsigned long size);
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extern int s390_enable_sie(void);
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/*
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* No page table caches to initialise
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@ -1798,6 +1798,8 @@ extern void mmput(struct mm_struct *);
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extern struct mm_struct *get_task_mm(struct task_struct *task);
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/* Remove the current tasks stale references to the old mm_struct */
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extern void mm_release(struct task_struct *, struct mm_struct *);
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/* Allocate a new mm structure and copy contents from tsk->mm */
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extern struct mm_struct *dup_mm(struct task_struct *tsk);
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extern int copy_thread(int, unsigned long, unsigned long, unsigned long, struct task_struct *, struct pt_regs *);
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extern void flush_thread(void);
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@ -521,7 +521,7 @@ void mm_release(struct task_struct *tsk, struct mm_struct *mm)
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* Allocate a new mm structure and copy contents from the
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* mm structure of the passed in task structure.
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*/
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static struct mm_struct *dup_mm(struct task_struct *tsk)
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struct mm_struct *dup_mm(struct task_struct *tsk)
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{
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struct mm_struct *mm, *oldmm = current->mm;
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int err;
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