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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 15:16:40 +0300
commitdef7ac806a9ac035abf0e7573ccc8bbfd38e163c (patch)
tree0487db594de37d6fcc0794d919627a89dd45b034
parent05dbcb430795b2e1fb1d5c757f8619d3dbed0a1c (diff)
downloadlinux-sh-def7ac806a9ac035abf0e7573ccc8bbfd38e163c.tar.gz
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)
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 */