@@ -33,6 +33,10 @@ the selector value is between 0x4000-0x7fff or 0xc000-0xffff.
NOTE: As of QEMU v2.4, writes to the fw_cfg data register are no
longer supported, and will be ignored (treated as no-ops)!
+NOTE: As of QEMU v2.9, writes are reinstated, but only through the DMA
+ interface (see below). Furthermore, writeability of any specific item is
+ governed independently of Bit14 in the selector key value.
+
Bit15 of the selector register indicates whether the configuration
setting is architecture specific. A value of 0 means the item is a
generic configuration item. A value of 1 means the item is specific
@@ -43,7 +47,7 @@ value between 0x8000-0xffff.
== Data Register ==
-* Read/Write (writes ignored as of QEMU v2.4)
+* Read/Write (writes ignored as of QEMU v2.4, but see the DMA interface)
* Location: platform dependent (IOport [*] or MMIO)
* Width: 8-bit (if IOport), 8/16/32/64-bit (if MMIO)
* Endianness: string-preserving
@@ -134,8 +138,8 @@ struct FWCfgFile { /* an individual file entry, 64 bytes total */
=== All Other Data Items ===
-Please consult the QEMU source for the most up-to-date and authoritative
-list of selector keys and their respective items' purpose and format.
+Please consult the QEMU source for the most up-to-date and authoritative list
+of selector keys and their respective items' purpose, format and writeability.
=== Ranges ===
@@ -144,9 +148,11 @@ items, and up to 0x4000 architecturally specific ones.
Selector Reg. Range Usage
--------------- -----------
-0x0000 - 0x3fff Generic (0x0000 - 0x3fff, RO)
+0x0000 - 0x3fff Generic (0x0000 - 0x3fff, generally RO, possibly RW through
+ the DMA interface in QEMU v2.9+)
0x4000 - 0x7fff Generic (0x0000 - 0x3fff, RW, ignored in QEMU v2.4+)
-0x8000 - 0xbfff Arch. Specific (0x0000 - 0x3fff, RO)
+0x8000 - 0xbfff Arch. Specific (0x0000 - 0x3fff, generally RO, possibly RW
+ through the DMA interface in QEMU v2.9+)
0xc000 - 0xffff Arch. Specific (0x0000 - 0x3fff, RW, ignored in v2.4+)
In practice, the number of allowed firmware configuration items is given
@@ -182,6 +188,7 @@ The "control" field has the following bits:
- Bit 1: Read
- Bit 2: Skip
- Bit 3: Select. The upper 16 bits are the selected index.
+ - Bit 4: Write
When an operation is triggered, if the "control" field has bit 3 set, the
upper 16 bits are interpreted as an index of a firmware configuration item.
@@ -191,8 +198,17 @@ If the "control" field has bit 1 set, a read operation will be performed.
"length" bytes for the current selector and offset will be copied into the
physical RAM address specified by the "address" field.
-If the "control" field has bit 2 set (and not bit 1), a skip operation will be
-performed. The offset for the current selector will be advanced "length" bytes.
+If the "control" field has bit 4 set (and not bit 1), a write operation will be
+performed. "length" bytes will be copied from the physical RAM address
+specified by the "address" field to the current selector and offset. QEMU
+prevents starting or finishing the write beyond the end of the item associated
+with the current selector (i.e., the item cannot be resized). Truncated writes
+are dropped entirely. Writes to read-only items are also rejected. All of these
+write errors set bit 0 (the error bit) in the "control" field.
+
+If the "control" field has bit 2 set (and neither bit 1 nor bit 4), a skip
+operation will be performed. The offset for the current selector will be
+advanced "length" bytes.
To check the result, read the "control" field:
error bit set -> something went wrong.
@@ -234,3 +250,5 @@ Prefix "opt/org.qemu/" is reserved for QEMU itself.
Use of names not beginning with "opt/" is potentially dangerous and
entirely unsupported. QEMU will warn if you try.
+
+All externally provided fw_cfg items are read-only to the guest.
@@ -75,7 +75,7 @@ static inline void hwsetup_create_rom(HWSetup *hw,
hwaddr base)
{
rom_add_blob("hwsetup", hw->data, TARGET_PAGE_SIZE,
- TARGET_PAGE_SIZE, base, NULL, NULL, NULL, NULL);
+ TARGET_PAGE_SIZE, base, NULL, NULL, NULL, NULL, true);
}
static inline void hwsetup_add_u8(HWSetup *hw, uint8_t u)
@@ -180,7 +180,8 @@ MemoryRegion *rom_add_blob(const char *name, const void *blob, size_t len,
size_t max_len, hwaddr addr,
const char *fw_file_name,
FWCfgReadCallback fw_callback,
- void *callback_opaque, AddressSpace *as);
+ void *callback_opaque, AddressSpace *as,
+ bool read_only);
int rom_add_elf_program(const char *name, void *data, size_t datasize,
size_t romsize, hwaddr addr, AddressSpace *as);
int rom_check_and_register_reset(void);
@@ -194,7 +195,7 @@ void hmp_info_roms(Monitor *mon, const QDict *qdict);
#define rom_add_file_fixed(_f, _a, _i) \
rom_add_file(_f, NULL, _a, _i, false, NULL, NULL)
#define rom_add_blob_fixed(_f, _b, _l, _a) \
- rom_add_blob(_f, _b, _l, _l, _a, NULL, NULL, NULL, NULL)
+ rom_add_blob(_f, _b, _l, _l, _a, NULL, NULL, NULL, NULL, true)
#define rom_add_file_mr(_f, _mr, _i) \
rom_add_file(_f, NULL, 0, _i, false, _mr, NULL)
#define rom_add_file_as(_f, _as, _i) \
@@ -202,7 +203,7 @@ void hmp_info_roms(Monitor *mon, const QDict *qdict);
#define rom_add_file_fixed_as(_f, _a, _i, _as) \
rom_add_file(_f, NULL, _a, _i, false, NULL, _as)
#define rom_add_blob_fixed_as(_f, _b, _l, _a, _as) \
- rom_add_blob(_f, _b, _l, _l, _a, NULL, NULL, NULL, _as)
+ rom_add_blob(_f, _b, _l, _l, _a, NULL, NULL, NULL, _as, true)
#define PC_ROM_MIN_VGA 0xc0000
#define PC_ROM_MIN_OPTION 0xc8000
@@ -136,6 +136,7 @@ void fw_cfg_add_file(FWCfgState *s, const char *filename, void *data,
* @callback_opaque: argument to be passed into callback function
* @data: pointer to start of item data
* @len: size of item data
+ * @read_only: is file read only
*
* Add a new NAMED fw_cfg item as a raw "blob" of the given size. The data
* referenced by the starting pointer is only linked, NOT copied, into the
@@ -151,7 +152,7 @@ void fw_cfg_add_file(FWCfgState *s, const char *filename, void *data,
*/
void fw_cfg_add_file_callback(FWCfgState *s, const char *filename,
FWCfgReadCallback callback, void *callback_opaque,
- void *data, size_t len);
+ void *data, size_t len, bool read_only);
/**
* fw_cfg_modify_file:
@@ -818,7 +818,7 @@ static MemoryRegion *acpi_add_rom_blob(AcpiBuildState *build_state,
uint64_t max_size)
{
return rom_add_blob(name, blob->data, acpi_data_len(blob), max_size, -1,
- name, virt_acpi_build_update, build_state, NULL);
+ name, virt_acpi_build_update, build_state, NULL, true);
}
static const VMStateDescription vmstate_virt_acpi_build = {
@@ -853,7 +853,7 @@ static void fw_cfg_resized(const char *id, uint64_t length, void *host)
}
}
-static void *rom_set_mr(Rom *rom, Object *owner, const char *name)
+static void *rom_set_mr(Rom *rom, Object *owner, const char *name, bool ro)
{
void *data;
@@ -862,7 +862,7 @@ static void *rom_set_mr(Rom *rom, Object *owner, const char *name)
rom->datasize, rom->romsize,
fw_cfg_resized,
&error_fatal);
- memory_region_set_readonly(rom->mr, true);
+ memory_region_set_readonly(rom->mr, ro);
vmstate_register_ram_global(rom->mr);
data = memory_region_get_ram_ptr(rom->mr);
@@ -942,7 +942,7 @@ int rom_add_file(const char *file, const char *fw_dir,
snprintf(devpath, sizeof(devpath), "/rom@%s", fw_file_name);
if ((!option_rom || mc->option_rom_has_mr) && mc->rom_file_has_mr) {
- data = rom_set_mr(rom, OBJECT(fw_cfg), devpath);
+ data = rom_set_mr(rom, OBJECT(fw_cfg), devpath, true);
} else {
data = rom->data;
}
@@ -979,7 +979,7 @@ err:
MemoryRegion *rom_add_blob(const char *name, const void *blob, size_t len,
size_t max_len, hwaddr addr, const char *fw_file_name,
FWCfgReadCallback fw_callback, void *callback_opaque,
- AddressSpace *as)
+ AddressSpace *as, bool read_only)
{
MachineClass *mc = MACHINE_GET_CLASS(qdev_get_machine());
Rom *rom;
@@ -998,10 +998,14 @@ MemoryRegion *rom_add_blob(const char *name, const void *blob, size_t len,
char devpath[100];
void *data;
- snprintf(devpath, sizeof(devpath), "/rom@%s", fw_file_name);
+ if (read_only) {
+ snprintf(devpath, sizeof(devpath), "/rom@%s", fw_file_name);
+ } else {
+ snprintf(devpath, sizeof(devpath), "/ram@%s", fw_file_name);
+ }
if (mc->rom_file_has_mr) {
- data = rom_set_mr(rom, OBJECT(fw_cfg), devpath);
+ data = rom_set_mr(rom, OBJECT(fw_cfg), devpath, read_only);
mr = rom->mr;
} else {
data = rom->data;
@@ -1009,7 +1013,7 @@ MemoryRegion *rom_add_blob(const char *name, const void *blob, size_t len,
fw_cfg_add_file_callback(fw_cfg, fw_file_name,
fw_callback, callback_opaque,
- data, rom->datasize);
+ data, rom->datasize, read_only);
}
return mr;
}
@@ -2936,7 +2936,7 @@ static MemoryRegion *acpi_add_rom_blob(AcpiBuildState *build_state,
uint64_t max_size)
{
return rom_add_blob(name, blob->data, acpi_data_len(blob), max_size, -1,
- name, acpi_build_update, build_state, NULL);
+ name, acpi_build_update, build_state, NULL, true);
}
static const VMStateDescription vmstate_acpi_build = {
@@ -3002,7 +3002,7 @@ void acpi_setup(void)
build_state->rsdp = g_memdup(tables.rsdp->data, rsdp_size);
fw_cfg_add_file_callback(pcms->fw_cfg, ACPI_BUILD_RSDP_FILE,
acpi_build_update, build_state,
- build_state->rsdp, rsdp_size);
+ build_state->rsdp, rsdp_size, true);
build_state->rsdp_mr = NULL;
} else {
build_state->rsdp = NULL;
@@ -54,11 +54,13 @@
#define FW_CFG_DMA_CTL_READ 0x02
#define FW_CFG_DMA_CTL_SKIP 0x04
#define FW_CFG_DMA_CTL_SELECT 0x08
+#define FW_CFG_DMA_CTL_WRITE 0x10
#define FW_CFG_DMA_SIGNATURE 0x51454d5520434647ULL /* "QEMU CFG" */
typedef struct FWCfgEntry {
uint32_t len;
+ bool allow_write;
uint8_t *data;
void *callback_opaque;
FWCfgReadCallback read_callback;
@@ -326,7 +328,7 @@ static void fw_cfg_dma_transfer(FWCfgState *s)
FWCfgDmaAccess dma;
int arch;
FWCfgEntry *e;
- int read;
+ int read = 0, write = 0;
dma_addr_t dma_addr;
/* Reset the address before the next access */
@@ -353,8 +355,13 @@ static void fw_cfg_dma_transfer(FWCfgState *s)
if (dma.control & FW_CFG_DMA_CTL_READ) {
read = 1;
+ write = 0;
+ } else if (dma.control & FW_CFG_DMA_CTL_WRITE) {
+ read = 0;
+ write = 1;
} else if (dma.control & FW_CFG_DMA_CTL_SKIP) {
read = 0;
+ write = 0;
} else {
dma.length = 0;
}
@@ -374,7 +381,9 @@ static void fw_cfg_dma_transfer(FWCfgState *s)
dma.control |= FW_CFG_DMA_CTL_ERROR;
}
}
-
+ if (write) {
+ dma.control |= FW_CFG_DMA_CTL_ERROR;
+ }
} else {
if (dma.length <= (e->len - s->cur_offset)) {
len = dma.length;
@@ -391,6 +400,14 @@ static void fw_cfg_dma_transfer(FWCfgState *s)
dma.control |= FW_CFG_DMA_CTL_ERROR;
}
}
+ if (write) {
+ if (!e->allow_write ||
+ len != dma.length ||
+ dma_memory_read(s->dma_as, dma.address,
+ &e->data[s->cur_offset], len)) {
+ dma.control |= FW_CFG_DMA_CTL_ERROR;
+ }
+ }
s->cur_offset += len;
}
@@ -586,7 +603,8 @@ static const VMStateDescription vmstate_fw_cfg = {
static void fw_cfg_add_bytes_read_callback(FWCfgState *s, uint16_t key,
FWCfgReadCallback callback,
void *callback_opaque,
- void *data, size_t len)
+ void *data, size_t len,
+ bool read_only)
{
int arch = !!(key & FW_CFG_ARCH_LOCAL);
@@ -599,6 +617,7 @@ static void fw_cfg_add_bytes_read_callback(FWCfgState *s, uint16_t key,
s->entries[arch][key].len = (uint32_t)len;
s->entries[arch][key].read_callback = callback;
s->entries[arch][key].callback_opaque = callback_opaque;
+ s->entries[arch][key].allow_write = !read_only;
}
static void *fw_cfg_modify_bytes_read(FWCfgState *s, uint16_t key,
@@ -616,13 +635,14 @@ static void *fw_cfg_modify_bytes_read(FWCfgState *s, uint16_t key,
s->entries[arch][key].data = data;
s->entries[arch][key].len = len;
s->entries[arch][key].callback_opaque = NULL;
+ s->entries[arch][key].allow_write = false;
return ptr;
}
void fw_cfg_add_bytes(FWCfgState *s, uint16_t key, void *data, size_t len)
{
- fw_cfg_add_bytes_read_callback(s, key, NULL, NULL, data, len);
+ fw_cfg_add_bytes_read_callback(s, key, NULL, NULL, data, len, true);
}
void fw_cfg_add_string(FWCfgState *s, uint16_t key, const char *value)
@@ -749,7 +769,7 @@ static int get_fw_cfg_order(FWCfgState *s, const char *name)
void fw_cfg_add_file_callback(FWCfgState *s, const char *filename,
FWCfgReadCallback callback, void *callback_opaque,
- void *data, size_t len)
+ void *data, size_t len, bool read_only)
{
int i, index, count;
size_t dsize;
@@ -811,7 +831,8 @@ void fw_cfg_add_file_callback(FWCfgState *s, const char *filename,
}
fw_cfg_add_bytes_read_callback(s, FW_CFG_FILE_FIRST + index,
- callback, callback_opaque, data, len);
+ callback, callback_opaque, data, len,
+ read_only);
s->files->f[index].size = cpu_to_be32(len);
s->files->f[index].select = cpu_to_be16(FW_CFG_FILE_FIRST + index);
@@ -824,7 +845,7 @@ void fw_cfg_add_file_callback(FWCfgState *s, const char *filename,
void fw_cfg_add_file(FWCfgState *s, const char *filename,
void *data, size_t len)
{
- fw_cfg_add_file_callback(s, filename, NULL, NULL, data, len);
+ fw_cfg_add_file_callback(s, filename, NULL, NULL, data, len, true);
}
void *fw_cfg_modify_file(FWCfgState *s, const char *filename,
@@ -847,7 +868,7 @@ void *fw_cfg_modify_file(FWCfgState *s, const char *filename,
}
}
/* add new one */
- fw_cfg_add_file_callback(s, filename, NULL, NULL, data, len);
+ fw_cfg_add_file_callback(s, filename, NULL, NULL, data, len, true);
return NULL;
}