Build and sysctl configuration modes are introduced for QAT SPR
devices to disable safe dc mode. A new QAT driver build option
‘QAT_DISABLE_SAFE_DC_MODE’ is required to build the QAT driver
with code that allows a request to be sent to FW to override the
‘History Buffer’ mitigation. Default QAT driver builds do not
include this ‘QAT_DISABLE_SAFE_DC_MODE’ build option. Even if the
QAT driver was built with code that allows a request to be sent to
FW to override the ‘History Buffer’ mitigation, the QAT driver must
still be configured using sysctl to request an override of the
‘History Buffer’ mitigation if desired. The default QAT driver
configuration option sysctl dev.qat.X.disable_safe_dc_mode does not
allow override of the mitigation. The new sysctl attribute
disable_safe_dc_mode is to be set to 1 for overriding the history
buffer mitigation. Firmware for qat_4xxx is updated for this change.
If this mode is enabled, decompression throughput increases but may
result in a data leak if num_user_processes is more than 1.
This option is to be enabled only if your system is not prone to
user data leaks.
Reviewed by: markj, ziaee
MFC after: 2 weeks
Sponsored by: Intel Corporation
Differential Revision: https://reviews.freebsd.org/D50379
5a8e5215ce