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