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s390: KVM preparation: provide hook to enable pgstes in user pagetable

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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 <[email protected]>
Signed-off-by: Carsten Otte <[email protected]>
Acked-by: Andrew Morton <[email protected]>
Signed-off-by: Avi Kivity <[email protected]>
This commit is contained in:
Carsten Otte 2008-03-25 18:47:10 +01:00 • committed by Avi Kivity
commit 402b08622d
8 changed files with 82 additions and 5 deletions
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1
include/asm-s390/mmu.h
View file

@ -7,6 +7,7 @@ typedef struct {
unsigned long asce_bits;
unsigned long asce_limit;
int noexec;
int pgstes;
} mm_context_t;
#endif

8
include/asm-s390/mmu_context.h
View file

@ -20,7 +20,13 @@ static inline int init_new_context(struct task_struct *tsk,
#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;

1
include/asm-s390/pgtable.h
View file

@ -966,6 +966,7 @@ static inline pte_t mk_swap_pte(unsigned long type, unsigned long offset)
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