docs: Add HTM to README.md

Signed-off-by: Cyril Bur <cyrilbur@gmail.com>

1 files changed, 24 insertions, 0 deletions

diff --git a/README.md b/README.md
index 95233bb..d0d621f 100644
--- a/README.md
+++ b/README.md
@@ -269,3 +269,27 @@ p0:c22:t0:spr008: 0xc0000000008a97f0
 p0t: 0 1 2 3 4 5 6 7
 c22: A A A A
 ```
+
+### Hardware Trace Macro
+Expoitation of HTM is limited to POWER9 NestHTM from the powerpc host.
+
+Using HTM requires a kernel built with both `CONFIG_PPC_MEMTRACE=y`
+(v4.14) and `CONFIG_SCOM_DEBUGFS=y`. debugfs should be mounted at
+`/sys/kernel/debug`.
+
+pdbg provides `htm_trace` which will configure the hardware and
+start tracing as well as `htm_analyse` which still stop the trace and
+dump the result to a file.
+
+```
+./pdbg -b host -d p9 -a htm_trace
+[allow test to run]
+./pdbg -b host -d p9 -a htm_analyse
+```
+If you are running into a checkstop issue, `htm_trace` will print the
+physical address of the buffer it is tracing into and the BMC can be
+used to recover this memory after checkstop see `getmem`.
+
+pdbg also provides some of the basic functionality to use HTM, such as
+`htm_reset`, `htm_start` and `htm_stop` to perform each step manually
+if required.