1 files changed, 217 insertions, 0 deletions
diff --git a/arch/x86/realmode/init.c b/arch/x86/realmode/init.c
new file mode 100644
index 000000000..af565816d
--- /dev/null
+++ b/arch/x86/realmode/init.c
@@ -0,0 +1,217 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/io.h>
+#include <linux/slab.h>
+#include <linux/memblock.h>
+#include <linux/cc_platform.h>
+#include <linux/pgtable.h>
+
+#include <asm/set_memory.h>
+#include <asm/realmode.h>
+#include <asm/tlbflush.h>
+#include <asm/crash.h>
+#include <asm/sev.h>
+
+struct real_mode_header *real_mode_header;
+u32 *trampoline_cr4_features;
+
+/* Hold the pgd entry used on booting additional CPUs */
+pgd_t trampoline_pgd_entry;
+
+void load_trampoline_pgtable(void)
+{
+#ifdef CONFIG_X86_32
+	load_cr3(initial_page_table);
+#else
+	/*
+	 * This function is called before exiting to real-mode and that will
+	 * fail with CR4.PCIDE still set.
+	 */
+	if (boot_cpu_has(X86_FEATURE_PCID))
+		cr4_clear_bits(X86_CR4_PCIDE);
+
+	write_cr3(real_mode_header->trampoline_pgd);
+#endif
+
+	/*
+	 * The CR3 write above will not flush global TLB entries.
+	 * Stale, global entries from previous page tables may still be
+	 * present.  Flush those stale entries.
+	 *
+	 * This ensures that memory accessed while running with
+	 * trampoline_pgd is *actually* mapped into trampoline_pgd.
+	 */
+	__flush_tlb_all();
+}
+
+void __init reserve_real_mode(void)
+{
+	phys_addr_t mem;
+	size_t size = real_mode_size_needed();
+
+	if (!size)
+		return;
+
+	WARN_ON(slab_is_available());
+
+	/* Has to be under 1M so we can execute real-mode AP code. */
+	mem = memblock_phys_alloc_range(size, PAGE_SIZE, 0, 1<<20);
+	if (!mem)
+		pr_info("No sub-1M memory is available for the trampoline\n");
+	else
+		set_real_mode_mem(mem);
+
+	/*
+	 * Unconditionally reserve the entire fisrt 1M, see comment in
+	 * setup_arch().
+	 */
+	memblock_reserve(0, SZ_1M);
+}
+
+static void __init sme_sev_setup_real_mode(struct trampoline_header *th)
+{
+#ifdef CONFIG_AMD_MEM_ENCRYPT
+	if (cc_platform_has(CC_ATTR_HOST_MEM_ENCRYPT))
+		th->flags |= TH_FLAGS_SME_ACTIVE;
+
+	if (cc_platform_has(CC_ATTR_GUEST_STATE_ENCRYPT)) {
+		/*
+		 * Skip the call to verify_cpu() in secondary_startup_64 as it
+		 * will cause #VC exceptions when the AP can't handle them yet.
+		 */
+		th->start = (u64) secondary_startup_64_no_verify;
+
+		if (sev_es_setup_ap_jump_table(real_mode_header))
+			panic("Failed to get/update SEV-ES AP Jump Table");
+	}
+#endif
+}
+
+static void __init setup_real_mode(void)
+{
+	u16 real_mode_seg;
+	const u32 *rel;
+	u32 count;
+	unsigned char *base;
+	unsigned long phys_base;
+	struct trampoline_header *trampoline_header;
+	size_t size = PAGE_ALIGN(real_mode_blob_end - real_mode_blob);
+#ifdef CONFIG_X86_64
+	u64 *trampoline_pgd;
+	u64 efer;
+	int i;
+#endif
+
+	base = (unsigned char *)real_mode_header;
+
+	/*
+	 * If SME is active, the trampoline area will need to be in
+	 * decrypted memory in order to bring up other processors
+	 * successfully. This is not needed for SEV.
+	 */
+	if (cc_platform_has(CC_ATTR_HOST_MEM_ENCRYPT))
+		set_memory_decrypted((unsigned long)base, size >> PAGE_SHIFT);
+
+	memcpy(base, real_mode_blob, size);
+
+	phys_base = __pa(base);
+	real_mode_seg = phys_base >> 4;
+
+	rel = (u32 *) real_mode_relocs;
+
+	/* 16-bit segment relocations. */
+	count = *rel++;
+	while (count--) {
+		u16 *seg = (u16 *) (base + *rel++);
+		*seg = real_mode_seg;
+	}
+
+	/* 32-bit linear relocations. */
+	count = *rel++;
+	while (count--) {
+		u32 *ptr = (u32 *) (base + *rel++);
+		*ptr += phys_base;
+	}
+
+	/* Must be performed *after* relocation. */
+	trampoline_header = (struct trampoline_header *)
+		__va(real_mode_header->trampoline_header);
+
+#ifdef CONFIG_X86_32
+	trampoline_header->start = __pa_symbol(startup_32_smp);
+	trampoline_header->gdt_limit = __BOOT_DS + 7;
+	trampoline_header->gdt_base = __pa_symbol(boot_gdt);
+#else
+	/*
+	 * Some AMD processors will #GP(0) if EFER.LMA is set in WRMSR
+	 * so we need to mask it out.
+	 */
+	rdmsrl(MSR_EFER, efer);
+	trampoline_header->efer = efer & ~EFER_LMA;
+
+	trampoline_header->start = (u64) secondary_startup_64;
+	trampoline_cr4_features = &trampoline_header->cr4;
+	*trampoline_cr4_features = mmu_cr4_features;
+
+	trampoline_header->flags = 0;
+
+	trampoline_pgd = (u64 *) __va(real_mode_header->trampoline_pgd);
+
+	/* Map the real mode stub as virtual == physical */
+	trampoline_pgd[0] = trampoline_pgd_entry.pgd;
+
+	/*
+	 * Include the entirety of the kernel mapping into the trampoline
+	 * PGD.  This way, all mappings present in the normal kernel page
+	 * tables are usable while running on trampoline_pgd.
+	 */
+	for (i = pgd_index(__PAGE_OFFSET); i < PTRS_PER_PGD; i++)
+		trampoline_pgd[i] = init_top_pgt[i].pgd;
+#endif
+
+	sme_sev_setup_real_mode(trampoline_header);
+}
+
+/*
+ * reserve_real_mode() gets called very early, to guarantee the
+ * availability of low memory. This is before the proper kernel page
+ * tables are set up, so we cannot set page permissions in that
+ * function. Also trampoline code will be executed by APs so we
+ * need to mark it executable at do_pre_smp_initcalls() at least,
+ * thus run it as a early_initcall().
+ */
+static void __init set_real_mode_permissions(void)
+{
+	unsigned char *base = (unsigned char *) real_mode_header;
+	size_t size = PAGE_ALIGN(real_mode_blob_end - real_mode_blob);
+
+	size_t ro_size =
+		PAGE_ALIGN(real_mode_header->ro_end) -
+		__pa(base);
+
+	size_t text_size =
+		PAGE_ALIGN(real_mode_header->ro_end) -
+		real_mode_header->text_start;
+
+	unsigned long text_start =
+		(unsigned long) __va(real_mode_header->text_start);
+
+	set_memory_nx((unsigned long) base, size >> PAGE_SHIFT);
+	set_memory_ro((unsigned long) base, ro_size >> PAGE_SHIFT);
+	set_memory_x((unsigned long) text_start, text_size >> PAGE_SHIFT);
+}
+
+void __init init_real_mode(void)
+{
+	if (!real_mode_header)
+		panic("Real mode trampoline was not allocated");
+
+	setup_real_mode();
+	set_real_mode_permissions();
+}
+
+static int __init do_init_real_mode(void)
+{
+	x86_platform.realmode_init();
+	return 0;
+}
+early_initcall(do_init_real_mode);