From bea41197ead3e03308bdd10c11db3ce91ae5c8ab Mon Sep 17 00:00:00 2001 From: Dominik Dingel Date: Thu, 25 Jun 2015 14:59:39 -0700 Subject: [PATCH] s390/mm: make hugepages_supported a boot time decision There is a potential bug with KVM and hugetlbfs if the hardware does not support hugepages (EDAT1). We fix this by making EDAT1 a hard requirement for hugepages and therefore removing and simplifying code. As s390, with the sw-emulated hugepages, was the only user of arch_prepare/release_hugepage I also removed theses calls from common and other architecture code. This patch (of 5): By dropping support for hugepages on machines which do not have the hardware feature EDAT1, we fix a potential s390 KVM bug. The bug would happen if a guest is backed by hugetlbfs (not supported currently), but does not get pagetables with PGSTE. This would lead to random memory overwrites. Signed-off-by: Dominik Dingel Acked-by: Martin Schwidefsky Cc: Heiko Carstens Cc: Christian Borntraeger Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- arch/s390/include/asm/page.h | 8 ++++---- arch/s390/kernel/setup.c | 2 ++ arch/s390/mm/pgtable.c | 2 ++ 3 files changed, 8 insertions(+), 4 deletions(-) diff --git a/arch/s390/include/asm/page.h b/arch/s390/include/asm/page.h index 53eacbd..0844b78 100644 --- a/arch/s390/include/asm/page.h +++ b/arch/s390/include/asm/page.h @@ -17,7 +17,10 @@ #define PAGE_DEFAULT_ACC 0 #define PAGE_DEFAULT_KEY (PAGE_DEFAULT_ACC << 4) -#define HPAGE_SHIFT 20 +#include +#ifndef __ASSEMBLY__ + +extern unsigned int HPAGE_SHIFT; #define HPAGE_SIZE (1UL << HPAGE_SHIFT) #define HPAGE_MASK (~(HPAGE_SIZE - 1)) #define HUGETLB_PAGE_ORDER (HPAGE_SHIFT - PAGE_SHIFT) @@ -27,9 +30,6 @@ #define ARCH_HAS_PREPARE_HUGEPAGE #define ARCH_HAS_HUGEPAGE_CLEAR_FLUSH -#include -#ifndef __ASSEMBLY__ - static inline void storage_key_init_range(unsigned long start, unsigned long end) { #if PAGE_DEFAULT_KEY diff --git a/arch/s390/kernel/setup.c b/arch/s390/kernel/setup.c index af4f41d..73941bf 100644 --- a/arch/s390/kernel/setup.c +++ b/arch/s390/kernel/setup.c @@ -880,6 +880,8 @@ void __init setup_arch(char **cmdline_p) */ setup_hwcaps(); + HPAGE_SHIFT = MACHINE_HAS_HPAGE ? 20 : 0; + /* * Create kernel page tables and switch to virtual addressing. */ diff --git a/arch/s390/mm/pgtable.c b/arch/s390/mm/pgtable.c index b33f661..16154720 100644 --- a/arch/s390/mm/pgtable.c +++ b/arch/s390/mm/pgtable.c @@ -31,6 +31,8 @@ #define ALLOC_ORDER 2 #define FRAG_MASK 0x03 +unsigned int HPAGE_SHIFT; + unsigned long *crst_table_alloc(struct mm_struct *mm) { struct page *page = alloc_pages(GFP_KERNEL, ALLOC_ORDER); -- 2.7.4