arch/x86/kernel/cc_platform.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Confidential Computing Platform Capability checks
   4  *
   5  * Copyright (C) 2021 Advanced Micro Devices, Inc.
   6  *
   7  * Author: Tom Lendacky <thomas.lendacky@amd.com>
   8  */
   9
  10 #include <linux/export.h>
  11 #include <linux/cc_platform.h>
  12 #include <linux/mem_encrypt.h>
  13
  14 #include <asm/processor.h>
  15
  16 static bool __maybe_unused intel_cc_platform_has(enum cc_attr attr)
  17 {
  18 #ifdef CONFIG_INTEL_TDX_GUEST
  19         return false;
  20 #else
  21         return false;
  22 #endif
  23 }
  24
  25 /*
  26  * SME and SEV are very similar but they are not the same, so there are
  27  * times that the kernel will need to distinguish between SME and SEV. The
  28  * cc_platform_has() function is used for this.  When a distinction isn't
  29  * needed, the CC_ATTR_MEM_ENCRYPT attribute can be used.
  30  *
  31  * The trampoline code is a good example for this requirement.  Before
  32  * paging is activated, SME will access all memory as decrypted, but SEV
  33  * will access all memory as encrypted.  So, when APs are being brought
  34  * up under SME the trampoline area cannot be encrypted, whereas under SEV
  35  * the trampoline area must be encrypted.
  36  */
  37 static bool amd_cc_platform_has(enum cc_attr attr)
  38 {
  39 #ifdef CONFIG_AMD_MEM_ENCRYPT
  40         switch (attr) {
  41         case CC_ATTR_MEM_ENCRYPT:
  42                 return sme_me_mask;
  43
  44         case CC_ATTR_HOST_MEM_ENCRYPT:
  45                 return sme_me_mask && !(sev_status & MSR_AMD64_SEV_ENABLED);
  46
  47         case CC_ATTR_GUEST_MEM_ENCRYPT:
  48                 return sev_status & MSR_AMD64_SEV_ENABLED;
  49
  50         case CC_ATTR_GUEST_STATE_ENCRYPT:
  51                 return sev_status & MSR_AMD64_SEV_ES_ENABLED;
  52
  53         default:
  54                 return false;
  55         }
  56 #else
  57         return false;
  58 #endif
  59 }
  60
  61
  62 bool cc_platform_has(enum cc_attr attr)
  63 {
  64         if (sme_me_mask)
  65                 return amd_cc_platform_has(attr);
  66
  67         return false;
  68 }
  69 EXPORT_SYMBOL_GPL(cc_platform_has);