root/arch/x86/boot/compressed/mem_encrypt.S

   1 /* SPDX-License-Identifier: GPL-2.0-only */
   2 /*
   3  * AMD Memory Encryption Support
   4  *
   5  * Copyright (C) 2017 Advanced Micro Devices, Inc.
   6  *
   7  * Author: Tom Lendacky <thomas.lendacky@amd.com>
   8  */
   9 
  10 #include <linux/linkage.h>
  11 
  12 #include <asm/processor-flags.h>
  13 #include <asm/msr.h>
  14 #include <asm/asm-offsets.h>
  15 
  16         .text
  17         .code32
  18 ENTRY(get_sev_encryption_bit)
  19         xor     %eax, %eax
  20 
  21 #ifdef CONFIG_AMD_MEM_ENCRYPT
  22         push    %ebx
  23         push    %ecx
  24         push    %edx
  25 
  26         /* Check if running under a hypervisor */
  27         movl    $1, %eax
  28         cpuid
  29         bt      $31, %ecx               /* Check the hypervisor bit */
  30         jnc     .Lno_sev
  31 
  32         movl    $0x80000000, %eax       /* CPUID to check the highest leaf */
  33         cpuid
  34         cmpl    $0x8000001f, %eax       /* See if 0x8000001f is available */
  35         jb      .Lno_sev
  36 
  37         /*
  38          * Check for the SEV feature:
  39          *   CPUID Fn8000_001F[EAX] - Bit 1
  40          *   CPUID Fn8000_001F[EBX] - Bits 5:0
  41          *     Pagetable bit position used to indicate encryption
  42          */
  43         movl    $0x8000001f, %eax
  44         cpuid
  45         bt      $1, %eax                /* Check if SEV is available */
  46         jnc     .Lno_sev
  47 
  48         movl    $MSR_AMD64_SEV, %ecx    /* Read the SEV MSR */
  49         rdmsr
  50         bt      $MSR_AMD64_SEV_ENABLED_BIT, %eax        /* Check if SEV is active */
  51         jnc     .Lno_sev
  52 
  53         movl    %ebx, %eax
  54         andl    $0x3f, %eax             /* Return the encryption bit location */
  55         jmp     .Lsev_exit
  56 
  57 .Lno_sev:
  58         xor     %eax, %eax
  59 
  60 .Lsev_exit:
  61         pop     %edx
  62         pop     %ecx
  63         pop     %ebx
  64 
  65 #endif  /* CONFIG_AMD_MEM_ENCRYPT */
  66 
  67         ret
  68 ENDPROC(get_sev_encryption_bit)
  69 
  70         .code64
  71 ENTRY(set_sev_encryption_mask)
  72 #ifdef CONFIG_AMD_MEM_ENCRYPT
  73         push    %rbp
  74         push    %rdx
  75 
  76         movq    %rsp, %rbp              /* Save current stack pointer */
  77 
  78         call    get_sev_encryption_bit  /* Get the encryption bit position */
  79         testl   %eax, %eax
  80         jz      .Lno_sev_mask
  81 
  82         bts     %rax, sme_me_mask(%rip) /* Create the encryption mask */
  83 
  84 .Lno_sev_mask:
  85         movq    %rbp, %rsp              /* Restore original stack pointer */
  86 
  87         pop     %rdx
  88         pop     %rbp
  89 #endif
  90 
  91         xor     %rax, %rax
  92         ret
  93 ENDPROC(set_sev_encryption_mask)
  94 
  95         .data
  96 
  97 #ifdef CONFIG_AMD_MEM_ENCRYPT
  98         .balign 8
  99 GLOBAL(sme_me_mask)
 100         .quad   0
 101 #endif