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| author | Martin Schwidefsky <schwidefsky@de.ibm.com> | 2016-02-24 12:18:50 +0300 |
|---|---|---|
| committer | Martin Schwidefsky <schwidefsky@de.ibm.com> | 2016-03-02 15:44:22 +0300 |
| commit | 443a813304ec36d4e81264b6a452a412a6b3ad9b (patch) | |
| tree | dfcbb07c4a35414bb7cd9d8faa08ab3c5ba6e991 /arch/s390/mm | |
| parent | 993e0681084c8e84dd870bffedec9410778dfa87 (diff) | |
| download | linux-443a813304ec36d4e81264b6a452a412a6b3ad9b.tar.xz | |
s390/kvm: simplify set_guest_storage_key
Git commit ab3f285f227fec62868037e9b1b1fd18294a83b8
"KVM: s390/mm: try a cow on read only pages for key ops"
added a fixup_user_fault to set_guest_storage_key force a copy on
write if the page is mapped read-only. This is supposed to fix the
problem of differing storage keys for shared mappings, e.g. the
empty_zero_page.
But if the storage key is set before the pte is mapped the storage
key update is done on the pgste. A later fault will happily map the
shared page with the key from the pgste.
Eventually git commit 2faee8ff9dc6f4bfe46f6d2d110add858140fb20
"s390/mm: prevent and break zero page mappings in case of storage keys"
fixed this problem for the empty_zero_page. The commit makes sure that
guests enabled for storage keys will not use the empty_zero_page at all.
As the call to fixup_user_fault in set_guest_storage_key depends on the
order of the storage key operation vs. the fault that maps the pte
it does not really fix anything. Just remove it.
Reviewed-by: Dominik Dingel <dingel@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Diffstat (limited to 'arch/s390/mm')
| -rw-r--r-- | arch/s390/mm/pgtable.c | 17 |
1 files changed, 0 insertions, 17 deletions
diff --git a/arch/s390/mm/pgtable.c b/arch/s390/mm/pgtable.c index 5109827883ac..6acd7174fe75 100644 --- a/arch/s390/mm/pgtable.c +++ b/arch/s390/mm/pgtable.c @@ -809,30 +809,13 @@ int set_guest_storage_key(struct mm_struct *mm, unsigned long addr, spinlock_t *ptl; pgste_t old, new; pte_t *ptep; - bool unlocked; down_read(&mm->mmap_sem); -retry: - unlocked = false; ptep = get_locked_pte(mm, addr, &ptl); if (unlikely(!ptep)) { up_read(&mm->mmap_sem); return -EFAULT; } - if (!(pte_val(*ptep) & _PAGE_INVALID) && - (pte_val(*ptep) & _PAGE_PROTECT)) { - pte_unmap_unlock(ptep, ptl); - /* - * We do not really care about unlocked. We will retry either - * way. But this allows fixup_user_fault to enable userfaultfd. - */ - if (fixup_user_fault(current, mm, addr, FAULT_FLAG_WRITE, - &unlocked)) { - up_read(&mm->mmap_sem); - return -EFAULT; - } - goto retry; - } new = old = pgste_get_lock(ptep); pgste_val(new) &= ~(PGSTE_GR_BIT | PGSTE_GC_BIT | |