Commit 6af7eea2 authored Apr 09, 2010 by Christian Borntraeger Committed by Martin Schwidefsky Apr 09, 2010

[S390] s390: disable change bit override



commit 6a985c61
([S390] s390: use change recording override for kernel mapping)
deactivated the change bit recording for the kernel mapping to
improve the performance. This works most of the time, but there
are cases (e.g. kernel runs in home space, futex atomic compare xcmg)
where we modify user memory with the kernel mapping instead of the
user mapping.
Instead of fixing these cases, this patch just deactivates change bit
override to avoid future problems with other kernel code that might
use the kernel mapping for user memory.

CC: stable@kernel.org
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

parent 176b1803

arch/s390/mm/vmem.c

+3 −8

Original line number	Diff line number	Diff line
		@@ -71,10 +71,6 @@ static pte_t __ref *vmem_pte_alloc(void)
		pte = alloc_bootmem(PTRS_PER_PTE * sizeof(pte_t));
		if (!pte)
		return NULL;
		if (MACHINE_HAS_HPAGE)
		clear_table((unsigned long *) pte, _PAGE_TYPE_EMPTY \| _PAGE_CO,
		PTRS_PER_PTE * sizeof(pte_t));
		else
		clear_table((unsigned long *) pte, _PAGE_TYPE_EMPTY,
		PTRS_PER_PTE * sizeof(pte_t));
		return pte;
		@@ -117,8 +113,7 @@ static int vmem_add_mem(unsigned long start, unsigned long size, int ro)
		if (MACHINE_HAS_HPAGE && !(address & ~HPAGE_MASK) &&
		(address + HPAGE_SIZE <= start + size) &&
		(address >= HPAGE_SIZE)) {
		pte_val(pte) \|= _SEGMENT_ENTRY_LARGE \|
		_SEGMENT_ENTRY_CO;
		pte_val(pte) \|= _SEGMENT_ENTRY_LARGE;
		pmd_val(*pm_dir) = pte_val(pte);
		address += HPAGE_SIZE - PAGE_SIZE;
		continue;

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