From 1366def38b6ab574dd0dbf95e308c7d115e73796 Mon Sep 17 00:00:00 2001
From: Heiko Carstens <heiko.carstens@de.ibm.com>
Date: Mon, 24 Apr 2017 15:27:35 +0200
Subject: [PATCH] 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: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
---
arch/s390/mm/pageattr.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)
diff --git a/arch/s390/mm/pageattr.c b/arch/s390/mm/pageattr.c
index fc5dc33bb1417..fc321c5ec30e0 100644
--- a/arch/s390/mm/pageattr.c
+++ b/arch/s390/mm/pageattr.c
@@ -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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