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KVM: s390: Allow skeys to be enabled for the current process

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Introduce a new function s390_enable_skey(), which enables storage key
handling via setting the use_skey flag in the mmu context.

This function is only useful within the context of kvm.

Note that enabling storage keys will cause a one-time hickup when
walking the page table; however, it saves us special effort for cases
like clear reset while making it possible for us to be architecture
conform.

s390_enable_skey() takes the page table lock to prevent reseting
storage keys triggered from multiple vcpus.

Signed-off-by: Dominik Dingel <dingel@linux.vnet.ibm.com>
Acked-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
This commit is contained in:
Dominik Dingel 2014-01-14 18:10:17 +01:00 committed by Christian Borntraeger
parent d4cb11340b
commit 934bc131ef
2 changed files with 24 additions and 0 deletions
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1
arch/s390/include/asm/pgtable.h
View File

@ -1747,6 +1747,7 @@ static inline pte_t mk_swap_pte(unsigned long type, unsigned long offset)
extern int vmem_add_mapping(unsigned long start, unsigned long size);
extern int vmem_remove_mapping(unsigned long start, unsigned long size);
extern int s390_enable_sie(void);
extern void s390_enable_skey(void);
/*
* No page table caches to initialise

23
arch/s390/mm/pgtable.c
View File

@ -1378,6 +1378,29 @@ int s390_enable_sie(void)
}
EXPORT_SYMBOL_GPL(s390_enable_sie);
/*
* Enable storage key handling from now on and initialize the storage
* keys with the default key.
*/
void s390_enable_skey(void)
{
/*
* To avoid races between multiple vcpus, ending in calling
* page_table_reset twice or more,
* the page_table_lock is taken for serialization.
*/
spin_lock(&current->mm->page_table_lock);
if (mm_use_skey(current->mm)) {
spin_unlock(&current->mm->page_table_lock);
return;
}
current->mm->context.use_skey = 1;
spin_unlock(&current->mm->page_table_lock);
page_table_reset_pgste(current->mm, 0, TASK_SIZE, true);
}
EXPORT_SYMBOL_GPL(s390_enable_skey);
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
int pmdp_clear_flush_young(struct vm_area_struct *vma, unsigned long address,
pmd_t *pmdp)