diff options
author | Gabriel Somlo <somlo@cmu.edu> | 2016-03-08 13:30:50 -0500 |
---|---|---|
committer | Michael S. Tsirkin <mst@redhat.com> | 2016-04-07 08:16:40 -0400 |
commit | def7ac806a9ac035abf0e7573ccc8bbfd38e163c (patch) | |
tree | 0487db594de37d6fcc0794d919627a89dd45b034 | |
parent | 05dbcb430795b2e1fb1d5c757f8619d3dbed0a1c (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.c | 16 |
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) | |||
77 | static inline void fw_cfg_read_blob(u16 key, | 77 | static 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 */ |