This patch adds the ability to load and link ACPI tables provided by QEMU.
QEMU tells guests how to load and patch ACPI tables through its fw_cfg
interface, by adding a firmware file 'etc/table-loader'. Guests are
supposed to parse this file and execute corresponding QEMU commands.

Signed-off-by: Miao Yan <yanmiaob...@gmail.com>
---
Changes in v2:
  - add function comment
  - improve error handling

 arch/x86/cpu/qemu/fw_cfg.c    | 253 ++++++++++++++++++++++++++++++++++++++++++
 arch/x86/include/asm/fw_cfg.h |  61 ++++++++++
 arch/x86/lib/acpi_table.c     |   4 +
 3 files changed, 318 insertions(+)

diff --git a/arch/x86/cpu/qemu/fw_cfg.c b/arch/x86/cpu/qemu/fw_cfg.c
index bcd34af..5ea7a6e 100644
--- a/arch/x86/cpu/qemu/fw_cfg.c
+++ b/arch/x86/cpu/qemu/fw_cfg.c
@@ -10,7 +10,10 @@
 #include <malloc.h>
 #include <asm/io.h>
 #include <asm/fw_cfg.h>
+#include <asm/tables.h>
+#include <asm/e820.h>
 #include <linux/list.h>
+#include <memalign.h>
 
 static bool fwcfg_present;
 static bool fwcfg_dma_present;
@@ -204,6 +207,256 @@ err:
        return -ENOMEM;
 }
 
+#ifdef CONFIG_QEMU_ACPI_TABLE
+static struct fw_file *qemu_fwcfg_find_file(const char *name)
+{
+       struct list_head *entry;
+       struct fw_file *file;
+
+       list_for_each(entry, &fw_list) {
+               file = list_entry(entry, struct fw_file, list);
+               if (!strcmp(file->cfg.name, name))
+                       return file;
+       }
+
+       return NULL;
+}
+
+/*
+ * This function allocates memory for ACPI tables
+ *
+ * @entry : BIOS linker command entry which tells where to allocate memory
+ *          (either high memory or low memory)
+ * @addr  : The address that should be used for low memory allcation. If the
+ *          memory allocation request is 'ZONE_HIGH' then this parameter will
+ *          be ignored.
+ * @return: 0 on success, or negative value on failure
+ */
+static int bios_linker_allocate(struct bios_linker_entry *entry,
+                          unsigned long *addr)
+{
+       uint32_t size, align;
+       struct fw_file *file;
+       unsigned long aligned_addr;
+
+       align = le32_to_cpu(entry->alloc.align);
+       /* align must be power of 2 */
+       if (align & (align - 1)) {
+               printf("error: wrong alignment %u\n", align);
+               return -EINVAL;
+       }
+
+       file = qemu_fwcfg_find_file(entry->alloc.file);
+       if (!file) {
+               printf("error: can't find file %s\n", entry->alloc.file);
+               return -ENOENT;
+       }
+
+       size = be32_to_cpu(file->cfg.size);
+
+       /*
+        * ZONE_HIGH means we need to allocate from high memory, since
+        * malloc space is already at the end of RAM, so we directly use it.
+        * If allocation zone is ZONE_FSEG, then we use the 'addr' passed
+        * in which is low memory
+        */
+       if (entry->alloc.zone == BIOS_LINKER_LOADER_ALLOC_ZONE_HIGH) {
+               aligned_addr = (unsigned long)memalign(align, size);
+               if (!aligned_addr) {
+                       printf("error: allocating resource\n");
+                       return -ENOMEM;
+               }
+       } else if (entry->alloc.zone == BIOS_LINKER_LOADER_ALLOC_ZONE_FSEG) {
+               aligned_addr = ALIGN(*addr, align);
+       } else {
+               printf("error: invalid allocation zone\n");
+               return -EINVAL;
+       }
+
+       debug("bios_linker_allocate: allocate file %s, size %u, zone %d, align 
%u, addr 0x%lx\n",
+             file->cfg.name, size, entry->alloc.zone, align, aligned_addr);
+
+       qemu_fwcfg_read_entry(be16_to_cpu(file->cfg.select),
+                             size, (void *)aligned_addr);
+       file->addr = aligned_addr;
+
+       /* adjust address for low memory allocation */
+       if (entry->alloc.zone == BIOS_LINKER_LOADER_ALLOC_ZONE_FSEG)
+               *addr = (aligned_addr + size);
+
+       return 0;
+}
+
+/*
+ * This function patches ACPI tables previously loaded
+ * by bios_linker_allocate()
+ *
+ * @entry : BIOS linker command entry which tells how to patch
+ *          ACPI tables
+ * @return: 0 on success, or negative value on failure
+ */
+static int bios_linker_add_pointer(struct bios_linker_entry *entry)
+{
+       struct fw_file *dest, *src;
+       uint32_t offset = le32_to_cpu(entry->pointer.offset);
+       uint64_t pointer = 0;
+
+       dest = qemu_fwcfg_find_file(entry->pointer.dest_file);
+       if (!dest || !dest->addr)
+               return -ENOENT;
+       src = qemu_fwcfg_find_file(entry->pointer.src_file);
+       if (!src || !src->addr)
+               return -ENOENT;
+
+       debug("bios_linker_add_pointer: dest->addr 0x%lx, src->addr 0x%lx, 
offset 0x%x size %u, 0x%llx\n",
+             dest->addr, src->addr, offset, entry->pointer.size, pointer);
+
+       memcpy(&pointer, (char *)dest->addr + offset, entry->pointer.size);
+       pointer = le64_to_cpu(pointer);
+       pointer += (unsigned long)src->addr;
+       pointer = cpu_to_le64(pointer);
+       memcpy((char *)dest->addr + offset, &pointer, entry->pointer.size);
+
+       return 0;
+}
+
+/*
+ * This function updates checksum fields of ACPI tables previously loaded
+ * by bios_linker_allocate()
+ *
+ * @entry : BIOS linker command entry which tells where to update ACPI table
+ *          checksums
+ * @return: 0 on success, or negative value on failure
+ */
+static int bios_linker_add_checksum(struct bios_linker_entry *entry)
+{
+       struct fw_file *file;
+       uint8_t *data, cksum = 0;
+       uint8_t *cksum_start;
+
+       file = qemu_fwcfg_find_file(entry->cksum.file);
+       if (!file || !file->addr)
+               return -ENOENT;
+
+       data = (uint8_t *)(file->addr + le32_to_cpu(entry->cksum.offset));
+       cksum_start = (uint8_t *)(file->addr + le32_to_cpu(entry->cksum.start));
+       cksum = table_compute_checksum(cksum_start,
+                                      le32_to_cpu(entry->cksum.length));
+       *data = cksum;
+
+       return 0;
+}
+
+unsigned install_e820_map(unsigned max_entries, struct e820entry *entries)
+{
+       entries[0].addr = 0;
+       entries[0].size = ISA_START_ADDRESS;
+       entries[0].type = E820_RAM;
+
+       entries[1].addr = ISA_START_ADDRESS;
+       entries[1].size = ISA_END_ADDRESS - ISA_START_ADDRESS;
+       entries[1].type = E820_RESERVED;
+
+       /*
+        * since we use memalign(malloc) to allocate high memory for
+        * storing ACPI tables, we need to reserve them in e820 tables,
+        * otherwise kernel will reclaim them and data will be corrupted
+        */
+       entries[2].addr = ISA_END_ADDRESS;
+       entries[2].size = gd->relocaddr - TOTAL_MALLOC_LEN - ISA_END_ADDRESS;
+       entries[2].type = E820_RAM;
+
+       /* for simplicity, reserve entire malloc space */
+       entries[3].addr = gd->relocaddr - TOTAL_MALLOC_LEN;
+       entries[3].size = TOTAL_MALLOC_LEN;
+       entries[3].type = E820_RESERVED;
+
+       entries[4].addr = gd->relocaddr;
+       entries[4].size = gd->ram_size - gd->relocaddr;
+       entries[4].type = E820_RESERVED;
+
+       entries[5].addr = CONFIG_PCIE_ECAM_BASE;
+       entries[5].size = CONFIG_PCIE_ECAM_SIZE;
+       entries[5].type = E820_RESERVED;
+
+       return 6;
+}
+
+/* This function loads and patches ACPI tables provided by QEMU */
+unsigned long write_acpi_tables(unsigned long addr)
+{
+       int i, ret = 0;
+       struct fw_file *file;
+       struct bios_linker_entry *table_loader;
+       struct bios_linker_entry *entry;
+       uint32_t size;
+       struct list_head *list;
+
+       /* make sure fw_list is loaded */
+       ret = qemu_fwcfg_read_firmware_list();
+       if (ret) {
+               printf("error: can't read firmware file list\n");
+               return addr;
+       }
+
+       file = qemu_fwcfg_find_file("etc/table-loader");
+       if (!file) {
+               printf("error: can't find etc/table-loader\n");
+               return addr;
+       }
+
+       size = be32_to_cpu(file->cfg.size);
+       if ((size % sizeof(*entry)) != 0) {
+               printf("error: table-loader maybe corrupted\n");
+               return addr;
+       }
+
+       table_loader = malloc(size);
+       if (!table_loader) {
+               printf("error: no memory for table-loader\n");
+               return addr;
+       }
+
+       qemu_fwcfg_read_entry(be16_to_cpu(file->cfg.select),
+                             size, table_loader);
+
+       for (i = 0; i < (size / sizeof(*entry)); i++) {
+               entry = table_loader + i;
+               switch (le32_to_cpu(entry->command)) {
+               case BIOS_LINKER_LOADER_COMMAND_ALLOCATE:
+                       ret = bios_linker_allocate(entry, &addr);
+                       if (ret)
+                               goto out;
+                       break;
+               case BIOS_LINKER_LOADER_COMMAND_ADD_POINTER:
+                       ret = bios_linker_add_pointer(entry);
+                       if (ret)
+                               goto out;
+                       break;
+               case BIOS_LINKER_LOADER_COMMAND_ADD_CHECKSUM:
+                       ret = bios_linker_add_checksum(entry);
+                       if (ret)
+                               goto out;
+                       break;
+               default:
+                       break;
+               }
+       }
+
+out:
+       if (ret) {
+               list_for_each(list, &fw_list) {
+                       file = list_entry(list, struct fw_file, list);
+                       if (file->addr)
+                               free((void *)file->addr);
+               }
+       }
+
+       free(table_loader);
+       return addr;
+}
+#endif
+
 static int qemu_fwcfg_list_firmware(void)
 {
        int ret;
diff --git a/arch/x86/include/asm/fw_cfg.h b/arch/x86/include/asm/fw_cfg.h
index 2acf43e..e9450c6 100644
--- a/arch/x86/include/asm/fw_cfg.h
+++ b/arch/x86/include/asm/fw_cfg.h
@@ -47,11 +47,23 @@ enum qemu_fwcfg_items {
        FW_CFG_INVALID          = 0xffff,
 };
 
+enum {
+       BIOS_LINKER_LOADER_COMMAND_ALLOCATE     = 0x1,
+       BIOS_LINKER_LOADER_COMMAND_ADD_POINTER  = 0x2,
+       BIOS_LINKER_LOADER_COMMAND_ADD_CHECKSUM = 0x3,
+};
+
+enum {
+       BIOS_LINKER_LOADER_ALLOC_ZONE_HIGH = 0x1,
+       BIOS_LINKER_LOADER_ALLOC_ZONE_FSEG = 0x2,
+};
+
 #define FW_CFG_FILE_SLOTS      0x10
 #define FW_CFG_MAX_ENTRY       (FW_CFG_FILE_FIRST + FW_CFG_FILE_SLOTS)
 #define FW_CFG_ENTRY_MASK       ~(FW_CFG_WRITE_CHANNEL | FW_CFG_ARCH_LOCAL)
 
 #define FW_CFG_MAX_FILE_PATH   56
+#define BIOS_LINKER_LOADER_FILESZ FW_CFG_MAX_FILE_PATH
 
 #define QEMU_FW_CFG_SIGNATURE  (('Q' << 24) | ('E' << 16) | ('M' << 8) | 'U')
 
@@ -81,6 +93,55 @@ struct fw_cfg_dma_access {
        __be64 address;
 };
 
+struct bios_linker_entry {
+       __le32 command;
+       union {
+               /*
+                * COMMAND_ALLOCATE - allocate a table from @alloc.file
+                * subject to @alloc.align alignment (must be power of 2)
+                * and @alloc.zone (can be HIGH or FSEG) requirements.
+                *
+                * Must appear exactly once for each file, and before
+                * this file is referenced by any other command.
+                */
+               struct {
+                       char file[BIOS_LINKER_LOADER_FILESZ];
+                       __le32 align;
+                       uint8_t zone;
+               } alloc;
+
+               /*
+                * COMMAND_ADD_POINTER - patch the table (originating from
+                * @dest_file) at @pointer.offset, by adding a pointer to the
+                * table originating from @src_file. 1,2,4 or 8 byte unsigned
+                * addition is used depending on @pointer.size.
+                */
+               struct {
+                       char dest_file[BIOS_LINKER_LOADER_FILESZ];
+                       char src_file[BIOS_LINKER_LOADER_FILESZ];
+                       __le32 offset;
+                       uint8_t size;
+               } pointer;
+
+               /*
+                * COMMAND_ADD_CHECKSUM - calculate checksum of the range
+                * specified by @cksum_start and @cksum_length fields,
+                * and then add the value at @cksum.offset.
+                * Checksum simply sums -X for each byte X in the range
+                * using 8-bit math.
+                */
+               struct {
+                       char file[BIOS_LINKER_LOADER_FILESZ];
+                       __le32 offset;
+                       __le32 start;
+                       __le32 length;
+               } cksum;
+
+               /* padding */
+               char pad[124];
+       };
+} __packed;
+
 /**
  * Initialize QEMU fw_cfg interface
  */
diff --git a/arch/x86/lib/acpi_table.c b/arch/x86/lib/acpi_table.c
index ab1db7e..2ec5ad2 100644
--- a/arch/x86/lib/acpi_table.c
+++ b/arch/x86/lib/acpi_table.c
@@ -331,6 +331,10 @@ static void acpi_create_ssdt_generator(acpi_header_t *ssdt,
        ssdt->checksum = table_compute_checksum((void *)ssdt, ssdt->length);
 }
 
+/*
+ * QEMU's version of write_acpi_tables is defined in
+ * arch/x86/cpu/qemu/fw_cfg.c
+ */
 unsigned long write_acpi_tables(unsigned long start)
 {
        unsigned long current;
-- 
1.9.1

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