init.c

  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
 15struct real_mode_header *real_mode_header;
 16u32 *trampoline_cr4_features;
 17
 18/* Hold the pgd entry used on booting additional CPUs */
 19pgd_t trampoline_pgd_entry;
 20
 21void 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
 47void __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
 73static 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
 92static 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 */
188static 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
209void __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
218static int __init do_init_real_mode(void)
219{
220	x86_platform.realmode_init();
221	return 0;
222}
223early_initcall(do_init_real_mode);