linux-kernel - [PATCH v2 16/17] tracing: Add config option for kexec handover

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Message-ID: <20231222195144.24532-11-graf@amazon.com>
Date: Fri, 22 Dec 2023 19:51:43 +0000
From: Alexander Graf <graf@...zon.com>
To: <linux-kernel@...r.kernel.org>
CC: <linux-trace-kernel@...r.kernel.org>, <linux-mm@...ck.org>,
	<devicetree@...r.kernel.org>, <linux-arm-kernel@...ts.infradead.org>,
	<kexec@...ts.infradead.org>, <linux-doc@...r.kernel.org>, <x86@...nel.org>,
	Eric Biederman <ebiederm@...ssion.com>, "H. Peter Anvin" <hpa@...or.com>,
	Andy Lutomirski <luto@...nel.org>, Peter Zijlstra <peterz@...radead.org>,
	"Rob Herring" <robh+dt@...nel.org>, Steven Rostedt <rostedt@...dmis.org>,
	"Andrew Morton" <akpm@...ux-foundation.org>, Mark Rutland
	<mark.rutland@....com>, "Tom Lendacky" <thomas.lendacky@....com>, Ashish
 Kalra <ashish.kalra@....com>, James Gowans <jgowans@...zon.com>, Stanislav
 Kinsburskii <skinsburskii@...ux.microsoft.com>, <arnd@...db.de>,
	<pbonzini@...hat.com>, <madvenka@...ux.microsoft.com>, Anthony Yznaga
	<anthony.yznaga@...cle.com>, Usama Arif <usama.arif@...edance.com>, David
 Woodhouse <dwmw@...zon.co.uk>, Benjamin Herrenschmidt
	<benh@...nel.crashing.org>
Subject: [PATCH v2 16/17] tracing: Add config option for kexec handover

Now that all bits are in place to allow ftrace to pass its trace data
into the next kernel on kexec, let's give users a kconfig option to
enable the functionality.

Signed-off-by: Alexander Graf <graf@...zon.com>

---

v1 -> v2:

  - Select crc32
---
 kernel/trace/Kconfig | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index 61c541c36596..418a5ae11aac 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -1169,6 +1169,20 @@ config HIST_TRIGGERS_DEBUG
 
           If unsure, say N.
 
+config FTRACE_KHO
+	bool "Ftrace Kexec handover support"
+	depends on KEXEC_KHO
+	select CRC32
+	help
+          Enable support for ftrace to pass metadata across kexec so the new
+	  kernel continues to use the previous kernel's trace buffers.
+
+	  This can be useful when debugging kexec performance or correctness
+	  issues: The new kernel can dump the old kernel's trace buffer which
+	  contains all events until reboot.
+
+	  If unsure, say N.
+
 source "kernel/trace/rv/Kconfig"
 
 endif # FTRACE
-- 
2.40.1




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