[RFC/PATCH 01/15] preparation: provide hook to enable pgstes in user pagetable

Carsten Otte
2008-03-20T16:24:38Z

From: Martin Schwidefsky <schwidefsky@de.ibm.com>

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.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Carsten Otte <cotte@de.ibm.com>
---

arch/s390/Kconfig | 4 ++
arch/s390/kernel/setup.c | 4 ++
arch/s390/mm/pgtable.c | 55 ++++++++++++++++++++++++++++++++++++++---
include/asm-s390/mmu.h | 1
include/asm-s390/mmu_context.h | 8 +++++
include/asm-s390/pgtable.h | 1
kernel/fork.c | 2 -
7 files changed, 70 insertions(+), 5 deletions(-)

Index: kvm/arch/s390/Kconfig
===================================================================
--- kvm.orig/arch/s390/Kconfig
+++ kvm/arch/s390/Kconfig
@@ -55,6 +55,10 @@ config GENERIC_LOCKBREAK
default y
depends on SMP && PREEMPT

+config PGSTE
+ bool
+ default y if KVM
+
mainmenu "Linux Kernel Configuration"

config S390
Index: kvm/arch/s390/kernel/setup.c
===================================================================
--- kvm.orig/arch/s390/kernel/setup.c
+++ kvm/arch/s390/kernel/setup.c
@@ -315,7 +315,11 @@ static int __init early_parse_ipldelay(c
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,
Index: kvm/arch/s390/mm/pgtable.c
===================================================================
--- kvm.orig/arch/s390/mm/pgtable.c
+++ kvm/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 m
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 m
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 *m
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 +247,33 @@ void disable_noexec(struct mm_struct *mm
mm->context.noexec = 0;
update_mm(mm, tsk);
}
+
+struct mm_struct *dup_mm(struct task_struct *tsk);
+
+/*
+ * switch on pgstes for its userspace process (for kvm)
+ */
+int s390_enable_sie(void)
+{
+ struct task_struct *tsk = current;
+ struct mm_struct *mm;
+
+ if (tsk->mm->context.pgstes)
+ return 0;
+ if (!tsk->mm || atomic_read(&tsk->mm->mm_users) > 1 ||
+ tsk->mm != tsk->active_mm || tsk->mm->ioctx_list)
+ return -EINVAL;
+ tsk->mm->context.pgstes = 1; /* dirty little tricks .. */
+ mm = dup_mm(tsk);
+ tsk->mm->context.pgstes = 0;
+ if (!mm)
+ return -ENOMEM;
+ 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();
+ return 0;
+}
+EXPORT_SYMBOL_GPL(s390_enable_sie);
Index: kvm/include/asm-s390/mmu.h
===================================================================
--- kvm.orig/include/asm-s390/mmu.h
+++ kvm/include/asm-s390/mmu.h
@@ -7,6 +7,7 @@ typedef struct {
unsigned long asce_bits;
unsigned long asce_limit;
int noexec;
+ int pgstes;
} mm_context_t;

#endif
Index: kvm/include/asm-s390/mmu_context.h
===================================================================
--- kvm.orig/include/asm-s390/mmu_context.h
+++ kvm/include/asm-s390/mmu_context.h
@@ -20,7 +20,13 @@ static inline int init_new_context(struc
#ifdef CONFIG_64BIT
mm->context.asce_bits |= _ASCE_TYPE_REGION3;
#endif
- mm->context.noexec = s390_noexec;
+ if (current->mm->context.pgstes) {
+ mm->context.noexec = 0;
+ mm->context.pgstes = 1;
+ } else {
+ mm->context.noexec = s390_noexec;
+ mm->context.pgstes = 0;
+ }
mm->context.asce_limit = STACK_TOP_MAX;
crst_table_init((unsigned long *) mm->pgd, pgd_entry_type(mm));
return 0;
Index: kvm/include/asm-s390/pgtable.h
===================================================================
--- kvm.orig/include/asm-s390/pgtable.h
+++ kvm/include/asm-s390/pgtable.h
@@ -966,6 +966,7 @@ static inline pte_t mk_swap_pte(unsigned

extern int add_shared_memory(unsigned long start, unsigned long size);
extern int remove_shared_memory(unsigned long start, unsigned long size);
+extern int s390_enable_sie(void);

/*
* No page table caches to initialise
Index: kvm/kernel/fork.c
===================================================================
--- kvm.orig/kernel/fork.c
+++ kvm/kernel/fork.c
@@ -498,7 +498,7 @@ void mm_release(struct task_struct *tsk,
* Allocate a new mm structure and copy contents from the
* mm structure of the passed in task structure.
*/
-static struct mm_struct *dup_mm(struct task_struct *tsk)
+struct mm_struct *dup_mm(struct task_struct *tsk)
{
struct mm_struct *mm, *oldmm = current->mm;
int err;