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authorGabriel Somlo <somlo@cmu.edu>2016-03-08 13:30:50 -0500
committerMichael S. Tsirkin <mst@redhat.com>2016-04-07 08:16:40 -0400
commitdef7ac806a9ac035abf0e7573ccc8bbfd38e163c (patch)
tree0487db594de37d6fcc0794d919627a89dd45b034
parent05dbcb430795b2e1fb1d5c757f8619d3dbed0a1c (diff)
firmware: qemu_fw_cfg.c: hold ACPI global lock during device access
Allowing for the future possibility of implementing AML-based (i.e., firmware-triggered) access to the QEMU fw_cfg device, acquire the global ACPI lock when accessing the device on behalf of the guest-side sysfs driver, to prevent any potential race conditions. Suggested-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Gabriel Somlo <somlo@cmu.edu> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
-rw-r--r--drivers/firmware/qemu_fw_cfg.c16
1 files changed, 16 insertions, 0 deletions
diff --git a/drivers/firmware/qemu_fw_cfg.c b/drivers/firmware/qemu_fw_cfg.c
index e4c471413d46..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)
77static inline void fw_cfg_read_blob(u16 key, 77static inline void fw_cfg_read_blob(u16 key,
78 void *buf, loff_t pos, size_t count) 78 void *buf, loff_t pos, size_t count)
79{ 79{
80 u32 glk;
81 acpi_status status;
82
83 /* If we have ACPI, ensure mutual exclusion against any potential
84 * device access by the firmware, e.g. via AML methods:
85 */
86 status = acpi_acquire_global_lock(ACPI_WAIT_FOREVER, &glk);
87 if (ACPI_FAILURE(status) && status != AE_NOT_CONFIGURED) {
88 /* Should never get here */
89 WARN(1, "fw_cfg_read_blob: Failed to lock ACPI!\n");
90 memset(buf, 0, count);
91 return;
92 }
93
80 mutex_lock(&fw_cfg_dev_lock); 94 mutex_lock(&fw_cfg_dev_lock);
81 iowrite16(fw_cfg_sel_endianness(key), fw_cfg_reg_ctrl); 95 iowrite16(fw_cfg_sel_endianness(key), fw_cfg_reg_ctrl);
82 while (pos-- > 0) 96 while (pos-- > 0)
83 ioread8(fw_cfg_reg_data); 97 ioread8(fw_cfg_reg_data);
84 ioread8_rep(fw_cfg_reg_data, buf, count); 98 ioread8_rep(fw_cfg_reg_data, buf, count);
85 mutex_unlock(&fw_cfg_dev_lock); 99 mutex_unlock(&fw_cfg_dev_lock);
100
101 acpi_release_global_lock(glk);
86} 102}
87 103
88/* clean up fw_cfg device i/o */ 104/* clean up fw_cfg device i/o */