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
 13#include <asm/coco.h>
 14#include <asm/processor.h>
 15
 16enum cc_vendor cc_vendor __ro_after_init = CC_VENDOR_NONE;
 17static u64 cc_mask __ro_after_init;
 18
 19static bool noinstr intel_cc_platform_has(enum cc_attr attr)
 20{
 21	switch (attr) {
 22	case CC_ATTR_GUEST_UNROLL_STRING_IO:
 23	case CC_ATTR_HOTPLUG_DISABLED:
 24	case CC_ATTR_GUEST_MEM_ENCRYPT:
 25	case CC_ATTR_MEM_ENCRYPT:
 26		return true;
 27	default:
 28		return false;
 29	}
 30}
 31
 32/*
 33 * Handle the SEV-SNP vTOM case where sme_me_mask is zero, and
 34 * the other levels of SME/SEV functionality, including C-bit
 35 * based SEV-SNP, are not enabled.
 36 */
 37static __maybe_unused __always_inline bool amd_cc_platform_vtom(enum cc_attr attr)
 38{
 39	switch (attr) {
 40	case CC_ATTR_GUEST_MEM_ENCRYPT:
 41	case CC_ATTR_MEM_ENCRYPT:
 42		return true;
 43	default:
 44		return false;
 45	}
 46}
 47
 48/*
 49 * SME and SEV are very similar but they are not the same, so there are
 50 * times that the kernel will need to distinguish between SME and SEV. The
 51 * cc_platform_has() function is used for this.  When a distinction isn't
 52 * needed, the CC_ATTR_MEM_ENCRYPT attribute can be used.
 53 *
 54 * The trampoline code is a good example for this requirement.  Before
 55 * paging is activated, SME will access all memory as decrypted, but SEV
 56 * will access all memory as encrypted.  So, when APs are being brought
 57 * up under SME the trampoline area cannot be encrypted, whereas under SEV
 58 * the trampoline area must be encrypted.
 59 */
 60
 61static bool noinstr amd_cc_platform_has(enum cc_attr attr)
 62{
 63#ifdef CONFIG_AMD_MEM_ENCRYPT
 64
 65	if (sev_status & MSR_AMD64_SNP_VTOM)
 66		return amd_cc_platform_vtom(attr);
 67
 68	switch (attr) {
 69	case CC_ATTR_MEM_ENCRYPT:
 70		return sme_me_mask;
 71
 72	case CC_ATTR_HOST_MEM_ENCRYPT:
 73		return sme_me_mask && !(sev_status & MSR_AMD64_SEV_ENABLED);
 74
 75	case CC_ATTR_GUEST_MEM_ENCRYPT:
 76		return sev_status & MSR_AMD64_SEV_ENABLED;
 77
 78	case CC_ATTR_GUEST_STATE_ENCRYPT:
 79		return sev_status & MSR_AMD64_SEV_ES_ENABLED;
 80
 81	/*
 82	 * With SEV, the rep string I/O instructions need to be unrolled
 83	 * but SEV-ES supports them through the #VC handler.
 84	 */
 85	case CC_ATTR_GUEST_UNROLL_STRING_IO:
 86		return (sev_status & MSR_AMD64_SEV_ENABLED) &&
 87			!(sev_status & MSR_AMD64_SEV_ES_ENABLED);
 88
 89	case CC_ATTR_GUEST_SEV_SNP:
 90		return sev_status & MSR_AMD64_SEV_SNP_ENABLED;
 91
 92	default:
 93		return false;
 94	}
 95#else
 96	return false;
 97#endif
 98}
 99
100bool noinstr cc_platform_has(enum cc_attr attr)
101{
102	switch (cc_vendor) {
103	case CC_VENDOR_AMD:
104		return amd_cc_platform_has(attr);
105	case CC_VENDOR_INTEL:
106		return intel_cc_platform_has(attr);
107	default:
108		return false;
109	}
110}
111EXPORT_SYMBOL_GPL(cc_platform_has);
112
113u64 cc_mkenc(u64 val)
114{
115	/*
116	 * Both AMD and Intel use a bit in the page table to indicate
117	 * encryption status of the page.
118	 *
119	 * - for AMD, bit *set* means the page is encrypted
120	 * - for AMD with vTOM and for Intel, *clear* means encrypted
121	 */
122	switch (cc_vendor) {
123	case CC_VENDOR_AMD:
124		if (sev_status & MSR_AMD64_SNP_VTOM)
125			return val & ~cc_mask;
126		else
127			return val | cc_mask;
128	case CC_VENDOR_INTEL:
129		return val & ~cc_mask;
130	default:
131		return val;
132	}
133}
134
135u64 cc_mkdec(u64 val)
136{
137	/* See comment in cc_mkenc() */
138	switch (cc_vendor) {
139	case CC_VENDOR_AMD:
140		if (sev_status & MSR_AMD64_SNP_VTOM)
141			return val | cc_mask;
142		else
143			return val & ~cc_mask;
144	case CC_VENDOR_INTEL:
145		return val | cc_mask;
146	default:
147		return val;
148	}
149}
150EXPORT_SYMBOL_GPL(cc_mkdec);
151
152__init void cc_set_mask(u64 mask)
153{
154	cc_mask = mask;
155}