Commit 1366def3 authored by Heiko Carstens's avatar Heiko Carstens Committed by Martin Schwidefsky
Browse files

s390/pageattr: avoid unnecessary page table splitting 



The kernel page table splitting code will split page tables even for
features the CPU does not support. E.g. a CPU may not support the NX
feature.
In order to avoid this, remove those bits from the flags parameter
that correlate with unsupported CPU features within __set_memory(). In
addition add an early exit if the flags parameter does not have any
bits set afterwards.

Signed-off-by: default avatarHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
parent 9b11c791

arch/s390/mm/pageattr.c

+7 −3
Original line number Diff line number Diff line
@@ -94,7 +94,7 @@ static int walk_pte_level(pmd_t *pmdp, unsigned long addr, unsigned long end, 
			new = pte_wrprotect(new);

		else if (flags & SET_MEMORY_RW)

			new = pte_mkwrite(pte_mkdirty(new));

		if ((flags & SET_MEMORY_NX) && MACHINE_HAS_NX)

		if (flags & SET_MEMORY_NX)

			pte_val(new) |= _PAGE_NOEXEC;

		else if (flags & SET_MEMORY_X)

			pte_val(new) &= ~_PAGE_NOEXEC;
@@ -144,7 +144,7 @@ static void modify_pmd_page(pmd_t *pmdp, unsigned long addr, 
		new = pmd_wrprotect(new);

	else if (flags & SET_MEMORY_RW)

		new = pmd_mkwrite(pmd_mkdirty(new));

	if ((flags & SET_MEMORY_NX) && MACHINE_HAS_NX)

	if (flags & SET_MEMORY_NX)

		pmd_val(new) |= _SEGMENT_ENTRY_NOEXEC;

	else if (flags & SET_MEMORY_X)

		pmd_val(new) &= ~_SEGMENT_ENTRY_NOEXEC;
@@ -221,7 +221,7 @@ static void modify_pud_page(pud_t *pudp, unsigned long addr, 
		new = pud_wrprotect(new);

	else if (flags & SET_MEMORY_RW)

		new = pud_mkwrite(pud_mkdirty(new));

	if ((flags & SET_MEMORY_NX) && MACHINE_HAS_NX)

	if (flags & SET_MEMORY_NX)

		pud_val(new) |= _REGION_ENTRY_NOEXEC;

	else if (flags & SET_MEMORY_X)

		pud_val(new) &= ~_REGION_ENTRY_NOEXEC;
@@ -288,6 +288,10 @@ static int change_page_attr(unsigned long addr, unsigned long end, 


int __set_memory(unsigned long addr, int numpages, unsigned long flags)

{

	if (!MACHINE_HAS_NX)

		flags &= ~(SET_MEMORY_NX | SET_MEMORY_X);

	if (!flags)

		return 0;

	addr &= PAGE_MASK;

	return change_page_attr(addr, addr + numpages * PAGE_SIZE, flags);

}

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