From 402b08622d9ac6e32e25289573272e0f21bb58a7 Mon Sep 17 00:00:00 2001 From: Carsten Otte Date: Tue, 25 Mar 2008 18:47:10 +0100 Subject: 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 Signed-off-by: Carsten Otte Acked-by: Andrew Morton Signed-off-by: Avi Kivity --- arch/s390/Kconfig | 4 +++ arch/s390/kernel/setup.c | 4 +++ arch/s390/mm/pgtable.c | 65 +++++++++++++++++++++++++++++++++++++++++++++--- 3 files changed, 70 insertions(+), 3 deletions(-) (limited to 'arch') diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig index f6a68e178fc5..513a0589e81d 100644 --- a/arch/s390/Kconfig +++ b/arch/s390/Kconfig @@ -62,6 +62,10 @@ config GENERIC_LOCKBREAK default y depends on SMP && PREEMPT +config PGSTE + bool + default y if KVM + mainmenu "Linux Kernel Configuration" config S390 diff --git a/arch/s390/kernel/setup.c b/arch/s390/kernel/setup.c index 7141147e6b63..2f35133ebc18 100644 --- a/arch/s390/kernel/setup.c +++ b/arch/s390/kernel/setup.c @@ -316,7 +316,11 @@ static int __init early_parse_ipldelay(char *p) early_param("ipldelay", early_parse_ipldelay); #ifdef CONFIG_S390_SWITCH_AMODE +#ifdef CONFIG_PGSTE +unsigned int switch_amode = 1; +#else unsigned int switch_amode = 0; +#endif EXPORT_SYMBOL_GPL(switch_amode); static void set_amode_and_uaccess(unsigned long user_amode, diff --git a/arch/s390/mm/pgtable.c b/arch/s390/mm/pgtable.c index fd072013f88c..5c1aea97cd12 100644 --- a/arch/s390/mm/pgtable.c +++ b/arch/s390/mm/pgtable.c @@ -30,11 +30,27 @@ #define TABLES_PER_PAGE 4 #define FRAG_MASK 15UL #define SECOND_HALVES 10UL + +void clear_table_pgstes(unsigned long *table) +{ + clear_table(table, _PAGE_TYPE_EMPTY, PAGE_SIZE/4); + memset(table + 256, 0, PAGE_SIZE/4); + clear_table(table + 512, _PAGE_TYPE_EMPTY, PAGE_SIZE/4); + memset(table + 768, 0, PAGE_SIZE/4); +} + #else #define ALLOC_ORDER 2 #define TABLES_PER_PAGE 2 #define FRAG_MASK 3UL #define SECOND_HALVES 2UL + +void clear_table_pgstes(unsigned long *table) +{ + clear_table(table, _PAGE_TYPE_EMPTY, PAGE_SIZE/2); + memset(table + 256, 0, PAGE_SIZE/2); +} + #endif unsigned long *crst_table_alloc(struct mm_struct *mm, int noexec) @@ -153,7 +169,7 @@ unsigned long *page_table_alloc(struct mm_struct *mm) unsigned long *table; unsigned long bits; - bits = mm->context.noexec ? 3UL : 1UL; + bits = (mm->context.noexec || mm->context.pgstes) ? 3UL : 1UL; spin_lock(&mm->page_table_lock); page = NULL; if (!list_empty(&mm->context.pgtable_list)) { @@ -170,7 +186,10 @@ unsigned long *page_table_alloc(struct mm_struct *mm) pgtable_page_ctor(page); page->flags &= ~FRAG_MASK; table = (unsigned long *) page_to_phys(page); - clear_table(table, _PAGE_TYPE_EMPTY, PAGE_SIZE); + if (mm->context.pgstes) + clear_table_pgstes(table); + else + clear_table(table, _PAGE_TYPE_EMPTY, PAGE_SIZE); spin_lock(&mm->page_table_lock); list_add(&page->lru, &mm->context.pgtable_list); } @@ -191,7 +210,7 @@ void page_table_free(struct mm_struct *mm, unsigned long *table) struct page *page; unsigned long bits; - bits = mm->context.noexec ? 3UL : 1UL; + bits = (mm->context.noexec || mm->context.pgstes) ? 3UL : 1UL; bits <<= (__pa(table) & (PAGE_SIZE - 1)) / 256 / sizeof(unsigned long); page = pfn_to_page(__pa(table) >> PAGE_SHIFT); spin_lock(&mm->page_table_lock); @@ -228,3 +247,43 @@ void disable_noexec(struct mm_struct *mm, struct task_struct *tsk) mm->context.noexec = 0; update_mm(mm, tsk); } + +/* + * switch on pgstes for its userspace process (for kvm) + */ +int s390_enable_sie(void) +{ + struct task_struct *tsk = current; + struct mm_struct *mm; + int rc; + + task_lock(tsk); + + rc = 0; + if (tsk->mm->context.pgstes) + goto unlock; + + rc = -EINVAL; + if (!tsk->mm || atomic_read(&tsk->mm->mm_users) > 1 || + tsk->mm != tsk->active_mm || tsk->mm->ioctx_list) + goto unlock; + + tsk->mm->context.pgstes = 1; /* dirty little tricks .. */ + mm = dup_mm(tsk); + tsk->mm->context.pgstes = 0; + + rc = -ENOMEM; + if (!mm) + goto unlock; + mmput(tsk->mm); + tsk->mm = tsk->active_mm = mm; + preempt_disable(); + update_mm(mm, tsk); + cpu_set(smp_processor_id(), mm->cpu_vm_mask); + preempt_enable(); + rc = 0; +unlock: + task_unlock(tsk); + return rc; +} +EXPORT_SYMBOL_GPL(s390_enable_sie); -- cgit v1.2.2