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authorMartin Schwidefsky <schwidefsky@de.ibm.com>2014-05-16 10:34:11 +0200
committerChristian Borntraeger <borntraeger@de.ibm.com>2014-05-16 14:57:17 +0200
commit3a801517ad49f586f2016e1b1321e6cd28a97a04 (patch)
treeb1d3a84ccbeb491202dd2b402463a0d9e454408f /arch/s390
parentd9f89b88f5102ce235b75a5907838e3c7ed84b97 (diff)
downloadop-kernel-dev-3a801517ad49f586f2016e1b1321e6cd28a97a04.zip
op-kernel-dev-3a801517ad49f586f2016e1b1321e6cd28a97a04.tar.gz
KVM: s390: correct locking for s390_enable_skey
Use the mm semaphore to serialize multiple invocations of s390_enable_skey. The second CPU faulting on a storage key operation needs to wait for the completion of the page table update. Taking the mm semaphore writable has the positive side-effect that it prevents any host faults from taking place which does have implications on keys vs PGSTE. Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Diffstat (limited to 'arch/s390')
-rw-r--r--arch/s390/mm/pgtable.c22
1 files changed, 7 insertions, 15 deletions
diff --git a/arch/s390/mm/pgtable.c b/arch/s390/mm/pgtable.c
index ea4a31b..66ba60c 100644
--- a/arch/s390/mm/pgtable.c
+++ b/arch/s390/mm/pgtable.c
@@ -958,8 +958,10 @@ void page_table_reset_pgste(struct mm_struct *mm, unsigned long start,
unsigned long addr, next;
pgd_t *pgd;
+ down_write(&mm->mmap_sem);
+ if (init_skey && mm_use_skey(mm))
+ goto out_up;
addr = start;
- down_read(&mm->mmap_sem);
pgd = pgd_offset(mm, addr);
do {
next = pgd_addr_end(addr, end);
@@ -967,7 +969,10 @@ void page_table_reset_pgste(struct mm_struct *mm, unsigned long start,
continue;
next = page_table_reset_pud(mm, pgd, addr, next, init_skey);
} while (pgd++, addr = next, addr != end);
- up_read(&mm->mmap_sem);
+ if (init_skey)
+ current->mm->context.use_skey = 1;
+out_up:
+ up_write(&mm->mmap_sem);
}
EXPORT_SYMBOL(page_table_reset_pgste);
@@ -1384,19 +1389,6 @@ EXPORT_SYMBOL_GPL(s390_enable_sie);
*/
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);
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