retbleed, тормоза и как отключить патч в 5.19

Here is currently a new patchset in testing which helps a bit with the performance and retbleed for intel:

+config CALL_DEPTH_TRACKING
+  bool "Mitigate RSB underflow with call depth tracking"
+  depends on CPU_SUP_INTEL && HAVE_CALL_THUNKS
+  select HAVE_DYNAMIC_FTRACE_NO_PATCHABLE
+  select CALL_THUNKS
+  default y
+  help
+    Compile the kernel with call depth tracking to mitigate the Intel
+    SKL Return-Speculation-Buffer (RSB) underflow issue. The
+    mitigation is off by default and needs to be enabled on the
+    kernel command line via the retbleed=stuff option. For
+    non-affected systems the overhead of this option is marginal as
+    the call depth tracking is using run-time generated call thunks
+    in a compiler generated padding area and call patching. This
+    increases text size by ~5%. For non affected systems this space
+    is unused. On affected SKL systems this results in a significant
+    performance gain over the IBRS mitigation.
+
+