From: Gabriel Somlo <somlo@xxxxxxx>
Instead of blindly probing fw_cfg registers at known IOport and MMIO
locations, use the ACPI subsystem to determine whether a QEMU fw_cfg
device is present, and, if found, to initialize it.
This limits portability to architectures which support ACPI (x86 and
UEFI-enabled aarch64), but avoids touching hardware registers before
being certain that our device is present.
NOTE: The standard way to verify the presence of fw_cfg on arm VMs
would have been to use the device tree, but that would have left out
x86, which is the primary architecture targeted by this patch.
Signed-off-by: Gabriel Somlo <somlo@xxxxxxx>
---
.../ABI/testing/sysfs-firmware-qemu_fw_cfg | 4 +
drivers/firmware/Kconfig | 2 +-
drivers/firmware/qemu_fw_cfg.c | 201 +++++++++++----------
3 files changed, 113 insertions(+), 94 deletions(-)
diff --git a/Documentation/ABI/testing/sysfs-firmware-qemu_fw_cfg b/Documentation/ABI/testing/sysfs-firmware-qemu_fw_cfg
index f1ef44e..e9761bf 100644
--- a/Documentation/ABI/testing/sysfs-firmware-qemu_fw_cfg
+++ b/Documentation/ABI/testing/sysfs-firmware-qemu_fw_cfg
@@ -76,6 +76,10 @@ Description:
the port number of the control register. I.e., the two ports
are overlapping, and can not be mapped separately.
+ NOTE 2. QEMU publishes the register details in the device tree
+ on arm guests, and in ACPI (under _HID "QEMU0002") on x86 and
+ select arm (aarch64) VM types.
+
=== Firmware Configuration Items of Interest ===
Originally, the index key, size, and formatting of blobs in
diff --git a/drivers/firmware/Kconfig b/drivers/firmware/Kconfig
index 0466e80..bc12d31 100644
--- a/drivers/firmware/Kconfig
+++ b/drivers/firmware/Kconfig
@@ -137,7 +137,7 @@ config ISCSI_IBFT
config FW_CFG_SYSFS
tristate "QEMU fw_cfg device support in sysfs"
- depends on SYSFS
+ depends on SYSFS && ACPI
default n
help
Say Y or M here to enable the exporting of the QEMU firmware
diff --git a/drivers/firmware/qemu_fw_cfg.c b/drivers/firmware/qemu_fw_cfg.c
index 3a67a16..f935afb 100644
--- a/drivers/firmware/qemu_fw_cfg.c
+++ b/drivers/firmware/qemu_fw_cfg.c
@@ -8,6 +8,7 @@
*/
#include <linux/module.h>
+#include <linux/acpi.h>
#include <linux/slab.h>
#include <linux/io.h>
#include <linux/ioport.h>
@@ -35,53 +36,10 @@ struct fw_cfg_file {
char name[FW_CFG_MAX_FILE_PATH];
};
-/* fw_cfg device i/o access options type */
-struct fw_cfg_access {
- const char *name;
- phys_addr_t base;
- u8 size;
- u8 ctrl_offset;
- u8 data_offset;
- bool is_mmio;
-};
-
-/* table of fw_cfg device i/o access options for known architectures */
-static struct fw_cfg_access fw_cfg_modes[] = {
- {
- .name = "fw_cfg IOport on i386, sun4u",
- .base = 0x510,
- .size = 0x02,
- .ctrl_offset = 0x00,
- .data_offset = 0x01,
- .is_mmio = false,
- }, {
- .name = "fw_cfg MMIO on arm",
- .base = 0x9020000,
- .size = 0x0a,
- .ctrl_offset = 0x08,
- .data_offset = 0x00,
- .is_mmio = true,
- }, {
- .name = "fw_cfg MMIO on sun4m",
- .base = 0xd00000510,
- .size = 0x03,
- .ctrl_offset = 0x00,
- .data_offset = 0x02,
- .is_mmio = true,
- }, {
- .name = "fw_cfg MMIO on ppc/mac",
- .base = 0xf0000510,
- .size = 0x03,
- .ctrl_offset = 0x00,
- .data_offset = 0x02,
- .is_mmio = true,
- }, { } /* END */
-};
-
-/* fw_cfg device i/o currently selected option set */
-static struct fw_cfg_access *fw_cfg_mode;
-
/* fw_cfg device i/o register addresses */
+static bool fw_cfg_is_mmio;
+static phys_addr_t fw_cfg_phys_base;
+static u32 fw_cfg_phys_size;
static void __iomem *fw_cfg_dev_base;
static void __iomem *fw_cfg_reg_ctrl;
static void __iomem *fw_cfg_reg_data;
@@ -92,7 +50,7 @@ static DEFINE_MUTEX(fw_cfg_dev_lock);
/* pick appropriate endianness for selector key */
static inline u16 fw_cfg_sel_endianness(u16 key)
{
- return fw_cfg_mode->is_mmio ? cpu_to_be16(key) : cpu_to_le16(key);
+ return fw_cfg_is_mmio ? cpu_to_be16(key) : cpu_to_le16(key);
}
/* type for fw_cfg "directory scan" visitor/callback function */
@@ -133,60 +91,100 @@ static inline void fw_cfg_read_blob(u16 key,
/* clean up fw_cfg device i/o */
static void fw_cfg_io_cleanup(void)
{
- if (fw_cfg_mode->is_mmio) {
+ if (fw_cfg_is_mmio) {
iounmap(fw_cfg_dev_base);
- release_mem_region(fw_cfg_mode->base, fw_cfg_mode->size);
+ release_mem_region(fw_cfg_phys_base, fw_cfg_phys_size);
} else {
ioport_unmap(fw_cfg_dev_base);
- release_region(fw_cfg_mode->base, fw_cfg_mode->size);
+ release_region(fw_cfg_phys_base, fw_cfg_phys_size);
}
}
-/* probe and map fw_cfg device */
-static int __init fw_cfg_io_probe(void)
+/* configure fw_cfg device i/o from ACPI _CRS method */
+static acpi_status fw_cfg_walk_crs(struct acpi_resource *r, void *context)
+{
+ struct acpi_resource_io *io;
+ struct acpi_resource_fixed_memory32 *mmio;
+
+ switch (r->type) {
+ case ACPI_RESOURCE_TYPE_END_TAG:
+ return AE_OK;
+ case ACPI_RESOURCE_TYPE_IO:
+ io = &r->data.io;
+ /* physical base addr should NOT be already set */
+ if (fw_cfg_phys_base)
+ return AE_ERROR;
+ if (!request_region(io->minimum,
+ io->address_length, "fw_cfg_io"))
+ return AE_ERROR;
+ fw_cfg_dev_base = ioport_map(io->minimum, io->address_length);
+ if (!fw_cfg_dev_base) {
+ release_region(io->minimum, io->address_length);
+ return AE_ERROR;
+ }
+ fw_cfg_phys_base = io->minimum;
+ fw_cfg_phys_size = io->address_length;
+ fw_cfg_is_mmio = false;
+ /* set register addresses (pc/i386 offsets) */
+ fw_cfg_reg_ctrl = fw_cfg_dev_base + 0x00;
+ fw_cfg_reg_data = fw_cfg_dev_base + 0x01;
+ return AE_OK;
+ case ACPI_RESOURCE_TYPE_FIXED_MEMORY32:
+ mmio = &r->data.fixed_memory32;
+ /* physical base addr should NOT be already set */
+ if (fw_cfg_phys_base)
+ return AE_ERROR;
+ /* MMIO and ACPI, but not on ARM ?!?! */
+ if (mmio->address_length < 0x0a)
+ return AE_ERROR;
+ if (!request_mem_region(mmio->address,
+ mmio->address_length, "fw_cfg_mem"))
+ return AE_ERROR;
+ fw_cfg_dev_base = ioremap(mmio->address, mmio->address_length);
+ if (!fw_cfg_dev_base) {
+ release_mem_region(mmio->address, mmio->address_length);
+ return AE_ERROR;
+ }
+ fw_cfg_phys_base = mmio->address;
+ fw_cfg_phys_size = mmio->address_length;
+ fw_cfg_is_mmio = true;
+ /* set register addresses (arm offsets) */
+ fw_cfg_reg_ctrl = fw_cfg_dev_base + 0x08;
+ fw_cfg_reg_data = fw_cfg_dev_base + 0x00;
+ return AE_OK;
+ default:
+ return AE_ERROR;
+ }
+}
+
+/* initialize fw_cfg device i/o from ACPI data */
+static int fw_cfg_acpi_init(struct acpi_device *dev)
{
char sig[FW_CFG_SIG_SIZE];
+ acpi_status status;
+ int err;
- for (fw_cfg_mode = &fw_cfg_modes[0];
- fw_cfg_mode->base; fw_cfg_mode++) {
-
- phys_addr_t base = fw_cfg_mode->base;
- u8 size = fw_cfg_mode->size;
-
- /* reserve and map mmio or ioport region */
- if (fw_cfg_mode->is_mmio) {
- if (!request_mem_region(base, size, fw_cfg_mode->name))
- continue;
- fw_cfg_dev_base = ioremap(base, size);
- if (!fw_cfg_dev_base) {
- release_mem_region(base, size);
- continue;
- }
- } else {
- if (!request_region(base, size, fw_cfg_mode->name))
- continue;
- fw_cfg_dev_base = ioport_map(base, size);
- if (!fw_cfg_dev_base) {
- release_region(base, size);
- continue;
- }
- }
+ err = acpi_bus_get_status(dev);
+ if (err < 0)
+ return err;
- /* set control and data register addresses */
- fw_cfg_reg_ctrl = fw_cfg_dev_base + fw_cfg_mode->ctrl_offset;
- fw_cfg_reg_data = fw_cfg_dev_base + fw_cfg_mode->data_offset;
+ if (!(dev->status.enabled && dev->status.functional))
+ return -ENODEV;
- /* verify fw_cfg device signature */
- fw_cfg_read_blob(FW_CFG_SIGNATURE, sig, 0, FW_CFG_SIG_SIZE);
- if (memcmp(sig, "QEMU", FW_CFG_SIG_SIZE) == 0)
- /* success, we're done */
- return 0;
+ /* extract device i/o details from _CRS */
+ status = acpi_walk_resources(dev->handle, METHOD_NAME__CRS,
+ fw_cfg_walk_crs, NULL);
+ if (status != AE_OK || !fw_cfg_phys_base)
+ return -ENODEV;
- /* clean up before probing next access mode */
+ /* verify fw_cfg device signature */
+ fw_cfg_read_blob(FW_CFG_SIGNATURE, sig, 0, FW_CFG_SIG_SIZE);
+ if (memcmp(sig, "QEMU", FW_CFG_SIG_SIZE) != 0) {
fw_cfg_io_cleanup();
+ return -ENODEV;
}
- return -ENODEV;
+ return 0;
}
/* fw_cfg revision attribute, in /sys/firmware/qemu_fw_cfg top-level dir. */
@@ -353,7 +351,7 @@ static struct kobject *fw_cfg_top_ko;
static struct kobject *fw_cfg_sel_ko;
/* callback function to register an individual fw_cfg file */
-static int __init fw_cfg_register_file(const struct fw_cfg_file *f)
+static int fw_cfg_register_file(const struct fw_cfg_file *f)
{
int err;
struct fw_cfg_sysfs_entry *entry;
@@ -397,12 +395,12 @@ static inline void fw_cfg_kobj_cleanup(struct kobject *kobj)
kobject_put(kobj);
}
-static int __init fw_cfg_sysfs_init(void)
+static int fw_cfg_sysfs_add(struct acpi_device *dev)
{
int err;
- /* probe for the fw_cfg "hardware" */
- err = fw_cfg_io_probe();
+ /* initialize fw_cfg device i/o from ACPI data */
+ err = fw_cfg_acpi_init(dev);
if (err)
return err;
@@ -443,14 +441,31 @@ err_top:
return err;
}
-static void __exit fw_cfg_sysfs_exit(void)
+static int fw_cfg_sysfs_remove(struct acpi_device *dev)
{
pr_debug("fw_cfg: unloading.\n");
fw_cfg_sysfs_cache_cleanup();
fw_cfg_kobj_cleanup(fw_cfg_sel_ko);
fw_cfg_kobj_cleanup(fw_cfg_top_ko);
fw_cfg_io_cleanup();
+ return 0;
}
-module_init(fw_cfg_sysfs_init);
-module_exit(fw_cfg_sysfs_exit);
+static const struct acpi_device_id fw_cfg_sysfs_device_ids[] = {
+ { "QEMU0002", 0 },
+ { "", 0 },
+};
+MODULE_DEVICE_TABLE(acpi, fw_cfg_sysfs_device_ids);
+
+static struct acpi_driver fw_cfg_sysfs_driver = {
+ .name = "fw_cfg",
+ .class = "QEMU",
+ .ids = fw_cfg_sysfs_device_ids,
+ .ops = {
+ .add = fw_cfg_sysfs_add,
+ .remove = fw_cfg_sysfs_remove,
+ },
+ .owner = THIS_MODULE,
+};
+
+module_acpi_driver(fw_cfg_sysfs_driver);
--
2.4.3
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