linux/arch/x86/boot/compressed/mem_encrypt.S
Tom Lendacky 07344b15a9 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 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
2018-03-28 10:42:57 +02:00

124 lines
2.4 KiB
ArmAsm

/*
* AMD Memory Encryption Support
*
* Copyright (C) 2017 Advanced Micro Devices, Inc.
*
* Author: Tom Lendacky <thomas.lendacky@amd.com>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <linux/linkage.h>
#include <asm/processor-flags.h>
#include <asm/msr.h>
#include <asm/asm-offsets.h>
.text
.code32
ENTRY(get_sev_encryption_bit)
xor %eax, %eax
#ifdef CONFIG_AMD_MEM_ENCRYPT
push %ebx
push %ecx
push %edx
push %edi
/*
* RIP-relative addressing is needed to access the encryption bit
* variable. Since we are running in 32-bit mode we need this call/pop
* sequence to get the proper relative addressing.
*/
call 1f
1: popl %edi
subl $1b, %edi
movl enc_bit(%edi), %eax
cmpl $0, %eax
jge .Lsev_exit
/* Check if running under a hypervisor */
movl $1, %eax
cpuid
bt $31, %ecx /* Check the hypervisor bit */
jnc .Lno_sev
movl $0x80000000, %eax /* CPUID to check the highest leaf */
cpuid
cmpl $0x8000001f, %eax /* See if 0x8000001f is available */
jb .Lno_sev
/*
* Check for the SEV feature:
* CPUID Fn8000_001F[EAX] - Bit 1
* CPUID Fn8000_001F[EBX] - Bits 5:0
* Pagetable bit position used to indicate encryption
*/
movl $0x8000001f, %eax
cpuid
bt $1, %eax /* Check if SEV is available */
jnc .Lno_sev
movl $MSR_AMD64_SEV, %ecx /* Read the SEV MSR */
rdmsr
bt $MSR_AMD64_SEV_ENABLED_BIT, %eax /* Check if SEV is active */
jnc .Lno_sev
movl %ebx, %eax
andl $0x3f, %eax /* Return the encryption bit location */
movl %eax, enc_bit(%edi)
jmp .Lsev_exit
.Lno_sev:
xor %eax, %eax
movl %eax, enc_bit(%edi)
.Lsev_exit:
pop %edi
pop %edx
pop %ecx
pop %ebx
#endif /* CONFIG_AMD_MEM_ENCRYPT */
ret
ENDPROC(get_sev_encryption_bit)
.code64
ENTRY(set_sev_encryption_mask)
#ifdef CONFIG_AMD_MEM_ENCRYPT
push %rbp
push %rdx
movq %rsp, %rbp /* Save current stack pointer */
call get_sev_encryption_bit /* Get the encryption bit position */
testl %eax, %eax
jz .Lno_sev_mask
bts %rax, sme_me_mask(%rip) /* Create the encryption mask */
.Lno_sev_mask:
movq %rbp, %rsp /* Restore original stack pointer */
pop %rdx
pop %rbp
#endif
xor %rax, %rax
ret
ENDPROC(set_sev_encryption_mask)
.data
enc_bit:
.int 0xffffffff
#ifdef CONFIG_AMD_MEM_ENCRYPT
.balign 8
GLOBAL(sme_me_mask)
.quad 0
#endif