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>hifive-unleashed-5.1
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05dbcb4307
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def7ac806a
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@ -77,12 +77,28 @@ static inline u16 fw_cfg_sel_endianness(u16 key)
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static inline void fw_cfg_read_blob(u16 key,
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static inline void fw_cfg_read_blob(u16 key,
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void *buf, loff_t pos, size_t count)
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void *buf, loff_t pos, size_t count)
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{
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{
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u32 glk;
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acpi_status status;
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/* If we have ACPI, ensure mutual exclusion against any potential
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* device access by the firmware, e.g. via AML methods:
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*/
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status = acpi_acquire_global_lock(ACPI_WAIT_FOREVER, &glk);
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if (ACPI_FAILURE(status) && status != AE_NOT_CONFIGURED) {
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/* Should never get here */
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WARN(1, "fw_cfg_read_blob: Failed to lock ACPI!\n");
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memset(buf, 0, count);
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return;
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}
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mutex_lock(&fw_cfg_dev_lock);
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mutex_lock(&fw_cfg_dev_lock);
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iowrite16(fw_cfg_sel_endianness(key), fw_cfg_reg_ctrl);
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iowrite16(fw_cfg_sel_endianness(key), fw_cfg_reg_ctrl);
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while (pos-- > 0)
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while (pos-- > 0)
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ioread8(fw_cfg_reg_data);
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ioread8(fw_cfg_reg_data);
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ioread8_rep(fw_cfg_reg_data, buf, count);
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ioread8_rep(fw_cfg_reg_data, buf, count);
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mutex_unlock(&fw_cfg_dev_lock);
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mutex_unlock(&fw_cfg_dev_lock);
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acpi_release_global_lock(glk);
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}
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}
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/* clean up fw_cfg device i/o */
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/* clean up fw_cfg device i/o */
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