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/*
* 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(get_sev_encryption_mask)
xor %rax, %rax
#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
xor %rdx, %rdx
bts %rax, %rdx /* Create the encryption mask */
mov %rdx, %rax /* ... and return it */
.Lno_sev_mask:
movq %rbp, %rsp /* Restore original stack pointer */
pop %rdx
pop %rbp
#endif
ret
ENDPROC(get_sev_encryption_mask)
.data
enc_bit:
.int 0xffffffff
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