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path: root/drivers/firmware/qemu_fw_cfg.c
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Diffstat (limited to 'drivers/firmware/qemu_fw_cfg.c')
-rw-r--r--drivers/firmware/qemu_fw_cfg.c24
1 files changed, 23 insertions, 1 deletions
diff --git a/drivers/firmware/qemu_fw_cfg.c b/drivers/firmware/qemu_fw_cfg.c
index fedbff55a7f3..815c4a5cae54 100644
--- a/drivers/firmware/qemu_fw_cfg.c
+++ b/drivers/firmware/qemu_fw_cfg.c
@@ -77,12 +77,28 @@ static inline u16 fw_cfg_sel_endianness(u16 key)
static inline void fw_cfg_read_blob(u16 key,
void *buf, loff_t pos, size_t count)
{
+ u32 glk;
+ acpi_status status;
+
+ /* If we have ACPI, ensure mutual exclusion against any potential
+ * device access by the firmware, e.g. via AML methods:
+ */
+ status = acpi_acquire_global_lock(ACPI_WAIT_FOREVER, &glk);
+ if (ACPI_FAILURE(status) && status != AE_NOT_CONFIGURED) {
+ /* Should never get here */
+ WARN(1, "fw_cfg_read_blob: Failed to lock ACPI!\n");
+ memset(buf, 0, count);
+ return;
+ }
+
mutex_lock(&fw_cfg_dev_lock);
iowrite16(fw_cfg_sel_endianness(key), fw_cfg_reg_ctrl);
while (pos-- > 0)
ioread8(fw_cfg_reg_data);
ioread8_rep(fw_cfg_reg_data, buf, count);
mutex_unlock(&fw_cfg_dev_lock);
+
+ acpi_release_global_lock(glk);
}
/* clean up fw_cfg device i/o */
@@ -727,12 +743,18 @@ device_param_cb(mmio, &fw_cfg_cmdline_param_ops, NULL, S_IRUSR);
static int __init fw_cfg_sysfs_init(void)
{
+ int ret;
+
/* create /sys/firmware/qemu_fw_cfg/ top level directory */
fw_cfg_top_ko = kobject_create_and_add("qemu_fw_cfg", firmware_kobj);
if (!fw_cfg_top_ko)
return -ENOMEM;
- return platform_driver_register(&fw_cfg_sysfs_driver);
+ ret = platform_driver_register(&fw_cfg_sysfs_driver);
+ if (ret)
+ fw_cfg_kobj_cleanup(fw_cfg_top_ko);
+
+ return ret;
}
static void __exit fw_cfg_sysfs_exit(void)