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

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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: Pavel Tatashin <pasha.tatashin@oracle.com>
Reviewed-by: Steven Sistare <steven.sistare@oracle.com>
Acked-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Pavel Tatashin 2018-01-15 11:44:14 -05:00 committed by Greg Kroah-Hartman
parent 92e8f20494
commit 1b92c48a2e
3 changed files with 12 additions and 8 deletions
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11
arch/x86/include/asm/pgalloc.h
View File

@ -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.
*/

7
arch/x86/mm/pgtable.c
View File

@ -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);

2
arch/x86/platform/efi/efi_64.c
View File

@ -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;