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Commit 07344b15 authored by Tom Lendacky's avatar Tom Lendacky Committed by Thomas Gleixner
Browse files

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



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 b83ce5ee ("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: b83ce5ee ("x86/mm/64: Make __PHYSICAL_MASK_SHIFT always 52")
Signed-off-by: default avatarTom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: default avatarThomas 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
parent 547edaca

arch/x86/boot/compressed/kaslr_64.c

+4 −10
Original line number Diff line number Diff line
@@ -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,

arch/x86/boot/compressed/mem_encrypt.S

+10 −7
Original line number Diff line number Diff line
@@ -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

arch/x86/boot/compressed/misc.h

+1 −1
Original line number Diff line number Diff line
@@ -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