Add support for GPF flows. It is found that the CXL specification around this to be a bit too involved from the driver side. And while this should really all handled by the hardware, this patch takes things with a grain of salt. Upon respective port enumeration, both phase timeouts are set to a max of 20 seconds, which is the NMI watchdog default for lockup detection. The premise is that the kernel does not have enough information to set anything better than a max across the board and hope devices finish their GPF flows within the platform energy budget. Timeout detection is based on dirty Shutdown semantics. The driver will mark it as dirty, expecting that the device clear it upon a successful GPF event. The admin may consult the device Health and check the dirty shutdown counter to see if there was a problem with data integrity. [ davej: Explicitly set return to 0 in update_gpf_port_dvsec() ] [ davej: Add spec reference for 'struct cxl_mbox_set_shutdown_state_in ] [ davej: Fix 0-day reported issue ] Signed-off-by: Davidlohr Bueso <dave@stgolabs.net> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com> Reviewed-by: Dan Williams <dan.j.williams@intel.com> Link: https://patch.msgid.link/20250124233533.910535-1-dave@stgolabs.net Signed-off-by: Dave Jiang <dave.jiang@intel.com>