linux-kernel - [PATCH 15/15] tracing: Add config option for kexec handover

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Message-ID: <20231213000452.88295-16-graf@amazon.com>
Date:   Wed, 13 Dec 2023 00:04:52 +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 15/15] 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>
---
 kernel/trace/Kconfig | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index 61c541c36596..af83ee755b9e 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -1169,6 +1169,19 @@ config HIST_TRIGGERS_DEBUG
 
           If unsure, say N.
 
+config FTRACE_KHO
+	bool "Ftrace Kexec handover support"
+	depends on KEXEC_KHO
+	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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