s390/mm: make hugepages_supported a boot time decision (bea41197) · Commits · 戴 / test

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 <dingel@linux.vnet.ibm.com> Acked-by:

Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: Heiko Carstens <heiko.carstens@de.ibm.com> Cc: Christian Borntraeger <borntraeger@de.ibm.com> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

arch/s390/include/asm/page.h

+4 −4

Original line number	Diff line number	Diff line
		@@ -17,7 +17,10 @@
		#define PAGE_DEFAULT_ACC 0
		#define PAGE_DEFAULT_KEY (PAGE_DEFAULT_ACC << 4)

		#define HPAGE_SHIFT 20
		#include <asm/setup.h>
		#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 <asm/setup.h>
		#ifndef __ASSEMBLY__

		static inline void storage_key_init_range(unsigned long start, unsigned long end)
		{
		#if PAGE_DEFAULT_KEY

arch/s390/kernel/setup.c

+2 −0

Original line number	Diff line number	Diff line
		@@ -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.
		*/

arch/s390/mm/pgtable.c

+2 −0

Original line number	Diff line number	Diff line
		@@ -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);

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