[PATCH] x86/kexec: Prepare ACPI table mapping for kexec kernel

[Baoquan He]

If the kernel decompressing code accesses ACPI tabels in kexec-ed kernel,
they also need be 1:1 mapped.

---
 arch/x86/kernel/machine_kexec_64.c | 54 ++++++++++++++++++++++++++++--
 1 file changed, 51 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c
index d5da54893f97..e2948aea27d4 100644
--- a/arch/x86/kernel/machine_kexec_64.c
+++ b/arch/x86/kernel/machine_kexec_64.c
@@ -30,6 +30,48 @@
 #include <asm/setup.h>
 #include <asm/set_memory.h>
 
+#ifdef CONFIG_ACPI
+/**
+ * Used while adding mapping for ACPI tables.
+ * Can be reused when other iomem regions need be mapped
+ */
+struct init_pgtable_data {
+	struct x86_mapping_info *info;
+	pgd_t *level4p;
+};
+
+static int mem_region_callback(struct resource *res, void *arg)
+{
+	struct init_pgtable_data *data= arg;
+	unsigned long mstart, mend;
+
+	mstart = res->start;
+	mend = mstart + resource_size(res) - 1;
+
+	return kernel_ident_mapping_init(data->info,
+			data->level4p, mstart, mend);
+}
+
+static int init_acpi_pgtable(struct x86_mapping_info *info,
+				   pgd_t *level4p)
+{
+	unsigned long flags = IORESOURCE_MEM | IORESOURCE_BUSY;
+	struct init_pgtable_data data;
+
+	data.info = info;
+	data.level4p = level4p;
+	flags = IORESOURCE_MEM | IORESOURCE_BUSY;
+	return walk_iomem_res_desc(IORES_DESC_ACPI_TABLES, flags, 0, -1,
+				   &data, mem_region_callback);
+}
+#else
+static int init_acpi_pgtable(struct x86_mapping_info *info,
+				   pgd_t *level4p)
+{
+	return 0;
+}
+#endif
+
 #ifdef CONFIG_KEXEC_FILE
 const struct kexec_file_ops * const kexec_file_loaders[] = {
 		&kexec_bzImage64_ops,
@@ -114,6 +156,8 @@ static void *alloc_pgt_page(void *data)
 	return p;
 }
 
+
+
 #ifdef CONFIG_EFI
 static int init_efi_systab_pgtable(struct x86_mapping_info *info,
 				   pgd_t *level4p)
@@ -191,14 +235,18 @@ static int init_pgtable(struct kimage *image, unsigned long start_pgtable)
 			return result;
 	}
 
-	/*
-	 * Prepare EFI systab mapping for kexec kernel, systab is not
-	 * covered by pfn_mapped.
+	/**
+	 * Prepare EFI systab and ACPI table mapping for kexec kernel,
+	 * since they are not covered by pfn_mapped.
 	 */
 	result = init_efi_systab_pgtable(&info, level4p);
 	if (result)
 		return result;
 
+	result = init_acpi_pgtable(&info, level4p);
+	if (result)
+		return result;
+
 	return init_transition_pgtable(image, level4p);
 }
 
-- 
2.17.2