Documentation: document the nosmt and smt s390 kernel parameters

Commit 6c2ff84e979a ("s390: add SMT support") added the nosmt and smt
early kernel parameters for restricting the use of symmetric
multithreading (SMT). They are quite useful for debugging and testing,
so document them.

Signed-off-by: Sascha Silbe <silbe@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index ecc74fa4bfde8a55d9fee00d96ae5ae4123560e9..92435e7c5f55e99f497847ef490c0cce524ec030 100644 (file)
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -2538,6 +2538,9 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 
        nohugeiomap     [KNL,x86] Disable kernel huge I/O mappings.
 
+       nosmt           [KNL,S390] Disable symmetric multithreading (SMT).
+                       Equivalent to smt=1.
+
        noxsave         [BUGS=X86] Disables x86 extended register state save
                        and restore using xsave. The kernel will fallback to
                        enabling legacy floating-point and sse state.
@@ -3695,6 +3698,13 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
                                1: Fast pin select (default)
                                2: ATC IRMode
 
+       smt             [KNL,S390] Set the maximum number of threads (logical
+                       CPUs) to use per physical CPU on systems capable of
+                       symmetric multithreading (SMT). Will be capped to the
+                       actual hardware limit.
+                       Format: <integer>
+                       Default: -1 (no limit)
+
        softlockup_panic=
                        [KNL] Should the soft-lockup detector generate panics.
                        Format: <integer>