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x86/boot: Fix SEV boot failure from change to __PHYSICAL_MASK_SHIFT

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In arch/x86/boot/compressed/kaslr_64.c, CONFIG_AMD_MEM_ENCRYPT support was
initially #undef'd to support SME with minimal effort.  When support for
SEV was added, the #undef remained and some minimal support for setting the
encryption bit was added for building identity mapped pagetable entries.

Commit b83ce5ee91 ("x86/mm/64: Make __PHYSICAL_MASK_SHIFT always 52")
changed __PHYSICAL_MASK_SHIFT from 46 to 52 in support of 5-level paging.
This change resulted in SEV guests failing to boot because the encryption
bit was no longer being automatically masked out.  The compressed boot
path now requires sme_me_mask to be defined in order for the pagetable
functions, such as pud_present(), to properly mask out the encryption bit
(currently bit 47) when evaluating pagetable entries.

Add an sme_me_mask variable in arch/x86/boot/compressed/mem_encrypt.S,
which is set when SEV is active, delete the #undef CONFIG_AMD_MEM_ENCRYPT
from arch/x86/boot/compressed/kaslr_64.c and use sme_me_mask when building
the identify mapped pagetable entries.

Fixes: b83ce5ee91 ("x86/mm/64: Make __PHYSICAL_MASK_SHIFT always 52")
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brijesh Singh <brijesh.singh@amd.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Link: https://lkml.kernel.org/r/20180327220711.8702.55842.stgit@tlendack-t1.amdoffice.net
This commit is contained in:
Tom Lendacky 2018-03-27 17:07:11 -05:00 committed by Thomas Gleixner
parent 547edaca24
commit 07344b15a9
3 changed files with 15 additions and 18 deletions
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14
arch/x86/boot/compressed/kaslr_64.c
View File

@ -16,13 +16,6 @@
#define __pa(x) ((unsigned long)(x))
#define __va(x) ((void *)((unsigned long)(x)))
/*
* The pgtable.h and mm/ident_map.c includes make use of the SME related
* information which is not used in the compressed image support. Un-define
* the SME support to avoid any compile and link errors.
*/
#undef CONFIG_AMD_MEM_ENCRYPT
/* No PAGE_TABLE_ISOLATION support needed either: */
#undef CONFIG_PAGE_TABLE_ISOLATION
@ -85,13 +78,14 @@ static struct x86_mapping_info mapping_info;
/* Locates and clears a region for a new top level page table. */
void initialize_identity_maps(void)
{
unsigned long sev_me_mask = get_sev_encryption_mask();
/* If running as an SEV guest, the encryption mask is required. */
set_sev_encryption_mask();
/* Init mapping_info with run-time function/buffer pointers. */
mapping_info.alloc_pgt_page = alloc_pgt_page;
mapping_info.context = &pgt_data;
mapping_info.page_flag = __PAGE_KERNEL_LARGE_EXEC | sev_me_mask;
mapping_info.kernpg_flag = _KERNPG_TABLE | sev_me_mask;
mapping_info.page_flag = __PAGE_KERNEL_LARGE_EXEC | sme_me_mask;
mapping_info.kernpg_flag = _KERNPG_TABLE;
/*
* It should be impossible for this not to already be true,

17
arch/x86/boot/compressed/mem_encrypt.S
View File

@ -88,9 +88,7 @@ ENTRY(get_sev_encryption_bit)
ENDPROC(get_sev_encryption_bit)
.code64
ENTRY(get_sev_encryption_mask)
xor %rax, %rax
ENTRY(set_sev_encryption_mask)
#ifdef CONFIG_AMD_MEM_ENCRYPT
push %rbp
push %rdx
@ -101,9 +99,7 @@ ENTRY(get_sev_encryption_mask)
testl %eax, %eax
jz .Lno_sev_mask
xor %rdx, %rdx
bts %rax, %rdx /* Create the encryption mask */
mov %rdx, %rax /* ... and return it */
bts %rax, sme_me_mask(%rip) /* Create the encryption mask */
.Lno_sev_mask:
movq %rbp, %rsp /* Restore original stack pointer */
@ -112,9 +108,16 @@ ENTRY(get_sev_encryption_mask)
pop %rbp
#endif
xor %rax, %rax
ret
ENDPROC(get_sev_encryption_mask)
ENDPROC(set_sev_encryption_mask)
.data
enc_bit:
.int 0xffffffff
#ifdef CONFIG_AMD_MEM_ENCRYPT
.balign 8
GLOBAL(sme_me_mask)
.quad 0
#endif

2
arch/x86/boot/compressed/misc.h
View File

@ -114,6 +114,6 @@ static inline void console_init(void)
{ }
#endif
unsigned long get_sev_encryption_mask(void);
void set_sev_encryption_mask(void);
#endif