1 // SPDX-License-Identifier: GPL-2.0
3 #include <linux/slab.h>
4 #include <linux/memblock.h>
5 #include <linux/mem_encrypt.h>
7 #include <asm/set_memory.h>
8 #include <asm/pgtable.h>
9 #include <asm/realmode.h>
10 #include <asm/tlbflush.h>
11 #include <asm/crash.h>
13 struct real_mode_header *real_mode_header;
14 u32 *trampoline_cr4_features;
16 /* Hold the pgd entry used on booting additional CPUs */
17 pgd_t trampoline_pgd_entry;
19 void load_trampoline_pgtable(void)
22 load_cr3(initial_page_table);
25 * This function is called before exiting to real-mode and that will
26 * fail with CR4.PCIDE still set.
28 if (boot_cpu_has(X86_FEATURE_PCID))
29 cr4_clear_bits(X86_CR4_PCIDE);
31 write_cr3(real_mode_header->trampoline_pgd);
35 * The CR3 write above will not flush global TLB entries.
36 * Stale, global entries from previous page tables may still be
37 * present. Flush those stale entries.
39 * This ensures that memory accessed while running with
40 * trampoline_pgd is *actually* mapped into trampoline_pgd.
45 void __init reserve_real_mode(void)
48 size_t size = real_mode_size_needed();
53 WARN_ON(slab_is_available());
55 /* Has to be under 1M so we can execute real-mode AP code. */
56 mem = memblock_find_in_range(0, 1<<20, size, PAGE_SIZE);
58 pr_info("No sub-1M memory is available for the trampoline\n");
62 memblock_reserve(mem, size);
63 set_real_mode_mem(mem);
64 crash_reserve_low_1M();
67 static void __init setup_real_mode(void)
73 unsigned long phys_base;
74 struct trampoline_header *trampoline_header;
75 size_t size = PAGE_ALIGN(real_mode_blob_end - real_mode_blob);
82 base = (unsigned char *)real_mode_header;
85 * If SME is active, the trampoline area will need to be in
86 * decrypted memory in order to bring up other processors
87 * successfully. This is not needed for SEV.
90 set_memory_decrypted((unsigned long)base, size >> PAGE_SHIFT);
92 memcpy(base, real_mode_blob, size);
94 phys_base = __pa(base);
95 real_mode_seg = phys_base >> 4;
97 rel = (u32 *) real_mode_relocs;
99 /* 16-bit segment relocations. */
102 u16 *seg = (u16 *) (base + *rel++);
103 *seg = real_mode_seg;
106 /* 32-bit linear relocations. */
109 u32 *ptr = (u32 *) (base + *rel++);
113 /* Must be perfomed *after* relocation. */
114 trampoline_header = (struct trampoline_header *)
115 __va(real_mode_header->trampoline_header);
118 trampoline_header->start = __pa_symbol(startup_32_smp);
119 trampoline_header->gdt_limit = __BOOT_DS + 7;
120 trampoline_header->gdt_base = __pa_symbol(boot_gdt);
123 * Some AMD processors will #GP(0) if EFER.LMA is set in WRMSR
124 * so we need to mask it out.
126 rdmsrl(MSR_EFER, efer);
127 trampoline_header->efer = efer & ~EFER_LMA;
129 trampoline_header->start = (u64) secondary_startup_64;
130 trampoline_cr4_features = &trampoline_header->cr4;
131 *trampoline_cr4_features = mmu_cr4_features;
133 trampoline_header->flags = 0;
135 trampoline_header->flags |= TH_FLAGS_SME_ACTIVE;
137 trampoline_pgd = (u64 *) __va(real_mode_header->trampoline_pgd);
139 /* Map the real mode stub as virtual == physical */
140 trampoline_pgd[0] = trampoline_pgd_entry.pgd;
143 * Include the entirety of the kernel mapping into the trampoline
144 * PGD. This way, all mappings present in the normal kernel page
145 * tables are usable while running on trampoline_pgd.
147 for (i = pgd_index(__PAGE_OFFSET); i < PTRS_PER_PGD; i++)
148 trampoline_pgd[i] = init_top_pgt[i].pgd;
153 * reserve_real_mode() gets called very early, to guarantee the
154 * availability of low memory. This is before the proper kernel page
155 * tables are set up, so we cannot set page permissions in that
156 * function. Also trampoline code will be executed by APs so we
157 * need to mark it executable at do_pre_smp_initcalls() at least,
158 * thus run it as a early_initcall().
160 static void __init set_real_mode_permissions(void)
162 unsigned char *base = (unsigned char *) real_mode_header;
163 size_t size = PAGE_ALIGN(real_mode_blob_end - real_mode_blob);
166 PAGE_ALIGN(real_mode_header->ro_end) -
170 PAGE_ALIGN(real_mode_header->ro_end) -
171 real_mode_header->text_start;
173 unsigned long text_start =
174 (unsigned long) __va(real_mode_header->text_start);
176 set_memory_nx((unsigned long) base, size >> PAGE_SHIFT);
177 set_memory_ro((unsigned long) base, ro_size >> PAGE_SHIFT);
178 set_memory_x((unsigned long) text_start, text_size >> PAGE_SHIFT);
181 static int __init init_real_mode(void)
183 if (!real_mode_header)
184 panic("Real mode trampoline was not allocated");
187 set_real_mode_permissions();
191 early_initcall(init_real_mode);