1 // SPDX-License-Identifier: GPL-2.0 2 #include <linux/io.h> 3 #include <linux/slab.h> 4 #include <linux/memblock.h> 5 #include <linux/cc_platform.h> 6 #include <linux/pgtable.h> 7 8 #include <asm/set_memory.h> 9 #include <asm/realmode.h> 10 #include <asm/tlbflush.h> 11 #include <asm/crash.h> 12 #include <asm/msr.h> 13 #include <asm/sev.h> 14 15 struct real_mode_header *real_mode_header; 16 u32 *trampoline_cr4_features; 17 18 /* Hold the pgd entry used on booting additional CPUs */ 19 pgd_t trampoline_pgd_entry; 20 21 void load_trampoline_pgtable(void) 22 { 23 #ifdef CONFIG_X86_32 24 load_cr3(initial_page_table); 25 #else 26 /* 27 * This function is called before exiting to real-mode and that will 28 * fail with CR4.PCIDE still set. 29 */ 30 if (boot_cpu_has(X86_FEATURE_PCID)) 31 cr4_clear_bits(X86_CR4_PCIDE); 32 33 write_cr3(real_mode_header->trampoline_pgd); 34 #endif 35 36 /* 37 * The CR3 write above will not flush global TLB entries. 38 * Stale, global entries from previous page tables may still be 39 * present. Flush those stale entries. 40 * 41 * This ensures that memory accessed while running with 42 * trampoline_pgd is *actually* mapped into trampoline_pgd. 43 */ 44 __flush_tlb_all(); 45 } 46 47 void __init reserve_real_mode(void) 48 { 49 phys_addr_t mem; 50 size_t size = real_mode_size_needed(); 51 52 if (!size) 53 return; 54 55 WARN_ON(slab_is_available()); 56 57 /* Has to be under 1M so we can execute real-mode AP code. */ 58 mem = memblock_phys_alloc_range(size, PAGE_SIZE, 0, 1<<20); 59 if (!mem) 60 pr_info("No sub-1M memory is available for the trampoline\n"); 61 else 62 set_real_mode_mem(mem); 63 64 /* 65 * Unconditionally reserve the entire first 1M, see comment in 66 * setup_arch(). 67 */ 68 memblock_reserve(0, SZ_1M); 69 70 memblock_clear_kho_scratch(0, SZ_1M); 71 } 72 73 static void __init sme_sev_setup_real_mode(struct trampoline_header *th) 74 { 75 #ifdef CONFIG_AMD_MEM_ENCRYPT 76 if (cc_platform_has(CC_ATTR_HOST_MEM_ENCRYPT)) 77 th->flags |= TH_FLAGS_SME_ACTIVE; 78 79 if (cc_platform_has(CC_ATTR_GUEST_STATE_ENCRYPT)) { 80 /* 81 * Skip the call to verify_cpu() in secondary_startup_64 as it 82 * will cause #VC exceptions when the AP can't handle them yet. 83 */ 84 th->start = (u64) secondary_startup_64_no_verify; 85 86 if (sev_es_setup_ap_jump_table(real_mode_header)) 87 panic("Failed to get/update SEV-ES AP Jump Table"); 88 } 89 #endif 90 } 91 92 static void __init setup_real_mode(void) 93 { 94 u16 real_mode_seg; 95 const u32 *rel; 96 u32 count; 97 unsigned char *base; 98 unsigned long phys_base; 99 struct trampoline_header *trampoline_header; 100 size_t size = PAGE_ALIGN(real_mode_blob_end - real_mode_blob); 101 #ifdef CONFIG_X86_64 102 u64 *trampoline_pgd; 103 u64 efer; 104 int i; 105 #endif 106 107 base = (unsigned char *)real_mode_header; 108 109 /* 110 * If SME is active, the trampoline area will need to be in 111 * decrypted memory in order to bring up other processors 112 * successfully. This is not needed for SEV. 113 */ 114 if (cc_platform_has(CC_ATTR_HOST_MEM_ENCRYPT)) 115 set_memory_decrypted((unsigned long)base, size >> PAGE_SHIFT); 116 117 memcpy(base, real_mode_blob, size); 118 119 phys_base = __pa(base); 120 real_mode_seg = phys_base >> 4; 121 122 rel = (u32 *) real_mode_relocs; 123 124 /* 16-bit segment relocations. */ 125 count = *rel++; 126 while (count--) { 127 u16 *seg = (u16 *) (base + *rel++); 128 *seg = real_mode_seg; 129 } 130 131 /* 32-bit linear relocations. */ 132 count = *rel++; 133 while (count--) { 134 u32 *ptr = (u32 *) (base + *rel++); 135 *ptr += phys_base; 136 } 137 138 /* Must be performed *after* relocation. */ 139 trampoline_header = (struct trampoline_header *) 140 __va(real_mode_header->trampoline_header); 141 142 #ifdef CONFIG_X86_32 143 trampoline_header->start = __pa_symbol(startup_32_smp); 144 trampoline_header->gdt_limit = __BOOT_DS + 7; 145 trampoline_header->gdt_base = __pa_symbol(boot_gdt); 146 #else 147 /* 148 * Some AMD processors will #GP(0) if EFER.LMA is set in WRMSR 149 * so we need to mask it out. 150 */ 151 rdmsrq(MSR_EFER, efer); 152 trampoline_header->efer = efer & ~EFER_LMA; 153 154 trampoline_header->start = (u64) secondary_startup_64; 155 trampoline_cr4_features = &trampoline_header->cr4; 156 *trampoline_cr4_features = mmu_cr4_features; 157 158 trampoline_header->flags = 0; 159 160 trampoline_lock = &trampoline_header->lock; 161 *trampoline_lock = 0; 162 163 trampoline_pgd = (u64 *) __va(real_mode_header->trampoline_pgd); 164 165 /* Map the real mode stub as virtual == physical */ 166 trampoline_pgd[0] = trampoline_pgd_entry.pgd; 167 168 /* 169 * Include the entirety of the kernel mapping into the trampoline 170 * PGD. This way, all mappings present in the normal kernel page 171 * tables are usable while running on trampoline_pgd. 172 */ 173 for (i = pgd_index(__PAGE_OFFSET); i < PTRS_PER_PGD; i++) 174 trampoline_pgd[i] = init_top_pgt[i].pgd; 175 #endif 176 177 sme_sev_setup_real_mode(trampoline_header); 178 } 179 180 /* 181 * reserve_real_mode() gets called very early, to guarantee the 182 * availability of low memory. This is before the proper kernel page 183 * tables are set up, so we cannot set page permissions in that 184 * function. Also trampoline code will be executed by APs so we 185 * need to mark it executable at do_pre_smp_initcalls() at least, 186 * thus run it as a early_initcall(). 187 */ 188 static void __init set_real_mode_permissions(void) 189 { 190 unsigned char *base = (unsigned char *) real_mode_header; 191 size_t size = PAGE_ALIGN(real_mode_blob_end - real_mode_blob); 192 193 size_t ro_size = 194 PAGE_ALIGN(real_mode_header->ro_end) - 195 __pa(base); 196 197 size_t text_size = 198 PAGE_ALIGN(real_mode_header->ro_end) - 199 real_mode_header->text_start; 200 201 unsigned long text_start = 202 (unsigned long) __va(real_mode_header->text_start); 203 204 set_memory_nx((unsigned long) base, size >> PAGE_SHIFT); 205 set_memory_ro((unsigned long) base, ro_size >> PAGE_SHIFT); 206 set_memory_x((unsigned long) text_start, text_size >> PAGE_SHIFT); 207 } 208 209 void __init init_real_mode(void) 210 { 211 if (!real_mode_header) 212 panic("Real mode trampoline was not allocated"); 213 214 setup_real_mode(); 215 set_real_mode_permissions(); 216 } 217 218 static int __init do_init_real_mode(void) 219 { 220 x86_platform.realmode_init(); 221 return 0; 222 } 223 early_initcall(do_init_real_mode); 224