arch/x86/boot/compressed/sev-es.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * AMD Encrypted Register State Support
   4  *
   5  * Author: Joerg Roedel <jroedel@suse.de>
   6  */
   7
   8 /*
   9  * misc.h needs to be first because it knows how to include the other kernel
  10  * headers in the pre-decompression code in a way that does not break
  11  * compilation.
  12  */
  13 #include "misc.h"
  14
  15 #include <asm/pgtable_types.h>
  16 #include <asm/sev-es.h>
  17 #include <asm/trapnr.h>
  18 #include <asm/trap_pf.h>
  19 #include <asm/msr-index.h>
  20 #include <asm/fpu/xcr.h>
  21 #include <asm/ptrace.h>
  22 #include <asm/svm.h>
  23
  24 #include "error.h"
  25
  26 struct ghcb boot_ghcb_page __aligned(PAGE_SIZE);
  27 struct ghcb *boot_ghcb;
  28
  29 /*
  30  * Copy a version of this function here - insn-eval.c can't be used in
  31  * pre-decompression code.
  32  */
  33 static bool insn_has_rep_prefix(struct insn *insn)
  34 {
  35         insn_byte_t p;
  36         int i;
  37
  38         insn_get_prefixes(insn);
  39
  40         for_each_insn_prefix(insn, i, p) {
  41                 if (p == 0xf2 || p == 0xf3)
  42                         return true;
  43         }
  44
  45         return false;
  46 }
  47
  48 /*
  49  * Only a dummy for insn_get_seg_base() - Early boot-code is 64bit only and
  50  * doesn't use segments.
  51  */
  52 static unsigned long insn_get_seg_base(struct pt_regs *regs, int seg_reg_idx)
  53 {
  54         return 0UL;
  55 }
  56
  57 static inline u64 sev_es_rd_ghcb_msr(void)
  58 {
  59         unsigned long low, high;
  60
  61         asm volatile("rdmsr" : "=a" (low), "=d" (high) :
  62                         "c" (MSR_AMD64_SEV_ES_GHCB));
  63
  64         return ((high << 32) | low);
  65 }
  66
  67 static inline void sev_es_wr_ghcb_msr(u64 val)
  68 {
  69         u32 low, high;
  70
  71         low  = val & 0xffffffffUL;
  72         high = val >> 32;
  73
  74         asm volatile("wrmsr" : : "c" (MSR_AMD64_SEV_ES_GHCB),
  75                         "a"(low), "d" (high) : "memory");
  76 }
  77
  78 static enum es_result vc_decode_insn(struct es_em_ctxt *ctxt)
  79 {
  80         char buffer[MAX_INSN_SIZE];
  81         enum es_result ret;
  82
  83         memcpy(buffer, (unsigned char *)ctxt->regs->ip, MAX_INSN_SIZE);
  84
  85         insn_init(&ctxt->insn, buffer, MAX_INSN_SIZE, 1);
  86         insn_get_length(&ctxt->insn);
  87
  88         ret = ctxt->insn.immediate.got ? ES_OK : ES_DECODE_FAILED;
  89
  90         return ret;
  91 }
  92
  93 static enum es_result vc_write_mem(struct es_em_ctxt *ctxt,
  94                                    void *dst, char *buf, size_t size)
  95 {
  96         memcpy(dst, buf, size);
  97
  98         return ES_OK;
  99 }
 100
 101 static enum es_result vc_read_mem(struct es_em_ctxt *ctxt,
 102                                   void *src, char *buf, size_t size)
 103 {
 104         memcpy(buf, src, size);
 105
 106         return ES_OK;
 107 }
 108
 109 #undef __init
 110 #undef __pa
 111 #define __init
 112 #define __pa(x) ((unsigned long)(x))
 113
 114 #define __BOOT_COMPRESSED
 115
 116 /* Basic instruction decoding support needed */
 117 #include "../../lib/inat.c"
 118 #include "../../lib/insn.c"
 119
 120 /* Include code for early handlers */
 121 #include "../../kernel/sev-es-shared.c"
 122
 123 static bool early_setup_sev_es(void)
 124 {
 125         if (!sev_es_negotiate_protocol())
 126                 sev_es_terminate(GHCB_SEV_ES_REASON_PROTOCOL_UNSUPPORTED);
 127
 128         if (set_page_decrypted((unsigned long)&boot_ghcb_page))
 129                 return false;
 130
 131         /* Page is now mapped decrypted, clear it */
 132         memset(&boot_ghcb_page, 0, sizeof(boot_ghcb_page));
 133
 134         boot_ghcb = &boot_ghcb_page;
 135
 136         /* Initialize lookup tables for the instruction decoder */
 137         inat_init_tables();
 138
 139         return true;
 140 }
 141
 142 void sev_es_shutdown_ghcb(void)
 143 {
 144         if (!boot_ghcb)
 145                 return;
 146
 147         if (!sev_es_check_cpu_features())
 148                 error("SEV-ES CPU Features missing.");
 149
 150         /*
 151          * GHCB Page must be flushed from the cache and mapped encrypted again.
 152          * Otherwise the running kernel will see strange cache effects when
 153          * trying to use that page.
 154          */
 155         if (set_page_encrypted((unsigned long)&boot_ghcb_page))
 156                 error("Can't map GHCB page encrypted");
 157
 158         /*
 159          * GHCB page is mapped encrypted again and flushed from the cache.
 160          * Mark it non-present now to catch bugs when #VC exceptions trigger
 161          * after this point.
 162          */
 163         if (set_page_non_present((unsigned long)&boot_ghcb_page))
 164                 error("Can't unmap GHCB page");
 165 }
 166
 167 bool sev_es_check_ghcb_fault(unsigned long address)
 168 {
 169         /* Check whether the fault was on the GHCB page */
 170         return ((address & PAGE_MASK) == (unsigned long)&boot_ghcb_page);
 171 }
 172
 173 void do_boot_stage2_vc(struct pt_regs *regs, unsigned long exit_code)
 174 {
 175         struct es_em_ctxt ctxt;
 176         enum es_result result;
 177
 178         if (!boot_ghcb && !early_setup_sev_es())
 179                 sev_es_terminate(GHCB_SEV_ES_REASON_GENERAL_REQUEST);
 180
 181         vc_ghcb_invalidate(boot_ghcb);
 182         result = vc_init_em_ctxt(&ctxt, regs, exit_code);
 183         if (result != ES_OK)
 184                 goto finish;
 185
 186         switch (exit_code) {
 187         case SVM_EXIT_RDTSC:
 188         case SVM_EXIT_RDTSCP:
 189                 result = vc_handle_rdtsc(boot_ghcb, &ctxt, exit_code);
 190                 break;
 191         case SVM_EXIT_IOIO:
 192                 result = vc_handle_ioio(boot_ghcb, &ctxt);
 193                 break;
 194         case SVM_EXIT_CPUID:
 195                 result = vc_handle_cpuid(boot_ghcb, &ctxt);
 196                 break;
 197         default:
 198                 result = ES_UNSUPPORTED;
 199                 break;
 200         }
 201
 202 finish:
 203         if (result == ES_OK) {
 204                 vc_finish_insn(&ctxt);
 205         } else if (result != ES_RETRY) {
 206                 /*
 207                  * For now, just halt the machine. That makes debugging easier,
 208                  * later we just call sev_es_terminate() here.
 209                  */
 210                 while (true)
 211                         asm volatile("hlt\n");
 212         }
 213 }