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s390/pageattr: do a single TLB flush for change_page_attr 

The change of the access rights for an address range in the kernel
address space is currently done with a loop of IPTE + a store of the
modified PTE. Between the IPTE and the store the PTE will be invalid,
this intermediate state can cause problems with concurrent accesses.

Consider a change of a kernel area from read-write to read-only, a
concurrent reader of that area should be fine but with the invalid
PTE it might get an unexpected exception.

Remove the IPTEs for each PTE and do a global flush after all PTEs
have been modified.

Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Martin Schwidefsky 2016-02-04 12:24:46 +01:00
parent 2cfc5f9ce7
commit 007ccec53d
1 changed files with 3 additions and 5 deletions
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8
arch/s390/mm/pageattr.c
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@ -65,19 +65,17 @@ static pte_t *walk_page_table(unsigned long addr)
static void change_page_attr(unsigned long addr, int numpages,
pte_t (*set) (pte_t))
{
pte_t *ptep, pte;
pte_t *ptep;
int i;
for (i = 0; i < numpages; i++) {
ptep = walk_page_table(addr);
if (WARN_ON_ONCE(!ptep))
break;
pte = *ptep;
pte = set(pte);
__ptep_ipte(addr, ptep);
*ptep = pte;
*ptep = set(*ptep);
addr += PAGE_SIZE;
}
__tlb_flush_kernel();
}
int set_memory_ro(unsigned long addr, int numpages)