linux-kernel - [PATCH V6 3/6] jump_label: Sort entries of the same key by the code

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Message-Id: <f57ae83e0592418ba269866bb7ade570fc8632e0.1560325897.git.bristot@redhat.com>
Date:   Wed, 12 Jun 2019 11:57:28 +0200
From:   Daniel Bristot de Oliveira <bristot@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        "Steven Rostedt (VMware)" <rostedt@...dmis.org>,
        Jiri Kosina <jkosina@...e.cz>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Chris von Recklinghausen <crecklin@...hat.com>,
        Jason Baron <jbaron@...mai.com>, Scott Wood <swood@...hat.com>,
        Marcelo Tosatti <mtosatti@...hat.com>,
        Clark Williams <williams@...hat.com>, x86@...nel.org
Subject: [PATCH V6 3/6] jump_label: Sort entries of the same key by the code

In the batching mode, all the entries of a given key are updated at once.
During the update of a key, a hit in the int3 handler will check if the
hitting code address belongs to one of these keys.

To optimize the search of a given code in the vector of entries being
updated, a binary search is used. The binary search relies on the order
of the entries of a key by its code. Hence the keys need to be sorted
by the code too, so sort the entries of a given key by the code.

Signed-off-by: Daniel Bristot de Oliveira <bristot@...hat.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Borislav Petkov <bp@...en8.de>
Cc: "H. Peter Anvin" <hpa@...or.com>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Masami Hiramatsu <mhiramat@...nel.org>
Cc: "Steven Rostedt (VMware)" <rostedt@...dmis.org>
Cc: Jiri Kosina <jkosina@...e.cz>
Cc: Josh Poimboeuf <jpoimboe@...hat.com>
Cc: "Peter Zijlstra (Intel)" <peterz@...radead.org>
Cc: Chris von Recklinghausen <crecklin@...hat.com>
Cc: Jason Baron <jbaron@...mai.com>
Cc: Scott Wood <swood@...hat.com>
Cc: Marcelo Tosatti <mtosatti@...hat.com>
Cc: Clark Williams <williams@...hat.com>
Cc: x86@...nel.org
Cc: linux-kernel@...r.kernel.org
---
 kernel/jump_label.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/kernel/jump_label.c b/kernel/jump_label.c
index 468ca421ad9a..2bd172e1e95f 100644
--- a/kernel/jump_label.c
+++ b/kernel/jump_label.c
@@ -37,12 +37,26 @@ static int jump_label_cmp(const void *a, const void *b)
 	const struct jump_entry *jea = a;
 	const struct jump_entry *jeb = b;
 
+	/*
+	 * Entrires are sorted by key.
+	 */
 	if (jump_entry_key(jea) < jump_entry_key(jeb))
 		return -1;
 
 	if (jump_entry_key(jea) > jump_entry_key(jeb))
 		return 1;
 
+	/*
+	 * In the batching mode, entries should also be sorted by the code
+	 * inside the already sorted list of entries, enabling a bsearch in
+	 * the vector.
+	 */
+	if (jump_entry_code(jea) < jump_entry_code(jeb))
+		return -1;
+
+	if (jump_entry_code(jea) > jump_entry_code(jeb))
+		return 1;
+
 	return 0;
 }
 
-- 
2.20.1