tools/trace: add Readme file

Signed-off-by: Yuri Benditovich <[email protected]>

Tools/trace/Readme.txt

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+This directory contains utilities for collecting traces from virtio-win
+kernel drivers (release builds). The drivers use Windows Event Tracing,
+so in order to make them to provide traces we Windows logger utility.
+
+Preparation:
+- Download entire 'trace' directory to the writable location on the VM
+  (assume this is Desktop\trace directory)
+
+Typical usage (collecting traces including driver initialization):
+- Disable the driver of the interest via Device Manager
+- Open administrator command prompt
+- pushd Desktop\trace
+- Run batch file for respective driver, for example "netkvm.bat", you will see:
+     "Recording started"
+     "Reproduce the problem, then press ENTER"
+- Enable the driver of the interest in the device Manager
+- When you decide to stop the tracing - press ENTER in the command-line window of the trace
+- Wait until the script finishes working, you will see:
+     "Please collect <drivername>.ETL file now"
+- The ETL file is a binary record. If you do not have the PDB file for the
+  installed build of the driver, you can submit this ETL file to the
+  problem report and provide the version of the target driver.
+
+You can also decode this ETL file to see a human-readable data. For that you need:
+- an exact PDB file (typically it is on the installation media in the same directory as
+  the installed driver)
+- two utilities from WDK installation: tracefmt.exe and tracepdb.exe
+  They are usually under C:\Program Files (x86)\Windows Kits\10\bin\...\x64
+  Place both utilities and the PDB file to the same "Desktop\trace" directory
+- From the same command line window type:
+  ParseTrace.bat <ETLFileName> <PDBFileName>
+
+For getting driver traces from the system boot, refer
+https://learn.microsoft.com/en-us/windows/win32/etw/configuring-and-starting-an-autologger-session