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Commit 1b92c48a authored by Pavel Tatashin's avatar Pavel Tatashin Committed by Greg Kroah-Hartman
Browse files

x86/pti/efi: broken conversion from efi to kernel page table 

The page table order must be increased for EFI table in order to avoid a
bug where NMI tries to change the page table to kernel page table, while
efi page table is active.

For more disccussion about this bug, see this thread:
http://lkml.iu.edu/hypermail/linux/kernel/1801.1/00951.html



Signed-off-by: default avatarPavel Tatashin <pasha.tatashin@oracle.com>
Reviewed-by: default avatarSteven Sistare <steven.sistare@oracle.com>
Acked-by: default avatarJiri Kosina <jkosina@suse.cz>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 92e8f204

arch/x86/include/asm/pgalloc.h

+11 −0
Original line number Diff line number Diff line
@@ -27,6 +27,17 @@ static inline void paravirt_release_pud(unsigned long pfn) {} 
 */

extern gfp_t __userpte_alloc_gfp;



#ifdef CONFIG_PAGE_TABLE_ISOLATION

/*

 * Instead of one PGD, we acquire two PGDs.  Being order-1, it is

 * both 8k in size and 8k-aligned.  That lets us just flip bit 12

 * in a pointer to swap between the two 4k halves.

 */

#define PGD_ALLOCATION_ORDER 1

#else

#define PGD_ALLOCATION_ORDER 0

#endif



/*

 * Allocate and free page tables.

 */

arch/x86/mm/pgtable.c

+0 −7
Original line number Diff line number Diff line
@@ -345,13 +345,6 @@ static inline void _pgd_free(pgd_t *pgd) 
}

#else



/*

 * Instead of one pgd, Kaiser acquires two pgds.  Being order-1, it is

 * both 8k in size and 8k-aligned.  That lets us just flip bit 12

 * in a pointer to swap between the two 4k halves.

 */

#define PGD_ALLOCATION_ORDER	kaiser_enabled



static inline pgd_t *_pgd_alloc(void)

{

	return (pgd_t *)__get_free_pages(PGALLOC_GFP, PGD_ALLOCATION_ORDER);

arch/x86/platform/efi/efi_64.c

+1 −1
Original line number Diff line number Diff line
@@ -142,7 +142,7 @@ int __init efi_alloc_page_tables(void) 
		return 0;



	gfp_mask = GFP_KERNEL | __GFP_NOTRACK | __GFP_ZERO;

	efi_pgd = (pgd_t *)__get_free_page(gfp_mask);

	efi_pgd = (pgd_t *)__get_free_pages(gfp_mask, PGD_ALLOCATION_ORDER);

	if (!efi_pgd)

		return -ENOMEM;