arch/x86/boot/compressed/mem_encrypt.S

   1 /*
   2  * AMD Memory Encryption Support
   3  *
   4  * Copyright (C) 2017 Advanced Micro Devices, Inc.
   5  *
   6  * Author: Tom Lendacky <thomas.lendacky@amd.com>
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License version 2 as
  10  * published by the Free Software Foundation.
  11  */
  12
  13 #include <linux/linkage.h>
  14
  15 #include <asm/processor-flags.h>
  16 #include <asm/msr.h>
  17 #include <asm/asm-offsets.h>
  18
  19         .text
  20         .code32
  21 ENTRY(get_sev_encryption_bit)
  22         xor     %eax, %eax
  23
  24 #ifdef CONFIG_AMD_MEM_ENCRYPT
  25         push    %ebx
  26         push    %ecx
  27         push    %edx
  28
  29         /* Check if running under a hypervisor */
  30         movl    $1, %eax
  31         cpuid
  32         bt      $31, %ecx               /* Check the hypervisor bit */
  33         jnc     .Lno_sev
  34
  35         movl    $0x80000000, %eax       /* CPUID to check the highest leaf */
  36         cpuid
  37         cmpl    $0x8000001f, %eax       /* See if 0x8000001f is available */
  38         jb      .Lno_sev
  39
  40         /*
  41          * Check for the SEV feature:
  42          *   CPUID Fn8000_001F[EAX] - Bit 1
  43          *   CPUID Fn8000_001F[EBX] - Bits 5:0
  44          *     Pagetable bit position used to indicate encryption
  45          */
  46         movl    $0x8000001f, %eax
  47         cpuid
  48         bt      $1, %eax                /* Check if SEV is available */
  49         jnc     .Lno_sev
  50
  51         movl    $MSR_AMD64_SEV, %ecx    /* Read the SEV MSR */
  52         rdmsr
  53         bt      $MSR_AMD64_SEV_ENABLED_BIT, %eax        /* Check if SEV is active */
  54         jnc     .Lno_sev
  55
  56         movl    %ebx, %eax
  57         andl    $0x3f, %eax             /* Return the encryption bit location */
  58         jmp     .Lsev_exit
  59
  60 .Lno_sev:
  61         xor     %eax, %eax
  62
  63 .Lsev_exit:
  64         pop     %edx
  65         pop     %ecx
  66         pop     %ebx
  67
  68 #endif  /* CONFIG_AMD_MEM_ENCRYPT */
  69
  70         ret
  71 ENDPROC(get_sev_encryption_bit)
  72
  73         .code64
  74 ENTRY(set_sev_encryption_mask)
  75 #ifdef CONFIG_AMD_MEM_ENCRYPT
  76         push    %rbp
  77         push    %rdx
  78
  79         movq    %rsp, %rbp              /* Save current stack pointer */
  80
  81         call    get_sev_encryption_bit  /* Get the encryption bit position */
  82         testl   %eax, %eax
  83         jz      .Lno_sev_mask
  84
  85         bts     %rax, sme_me_mask(%rip) /* Create the encryption mask */
  86
  87 .Lno_sev_mask:
  88         movq    %rbp, %rsp              /* Restore original stack pointer */
  89
  90         pop     %rdx
  91         pop     %rbp
  92 #endif
  93
  94         xor     %rax, %rax
  95         ret
  96 ENDPROC(set_sev_encryption_mask)
  97
  98         .data
  99
 100 #ifdef CONFIG_AMD_MEM_ENCRYPT
 101         .balign 8
 102 GLOBAL(sme_me_mask)
 103         .quad   0
 104 #endif