linux-kernel - [PATCH 1/8] fpu/init: Get rid of two redundant clts() calls

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Mon, 31 Oct 2016 15:18:42 -0700
From:   Andy Lutomirski <luto@...nel.org>
To:     x86@...nel.org
Cc:     Borislav Petkov <bp@...en8.de>, linux-kernel@...r.kernel.org,
        Rusty Russell <rusty@...tcorp.com.au>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Rik van Riel <riel@...hat.com>,
        kvm list <kvm@...r.kernel.org>,
        Andy Lutomirski <luto@...nel.org>
Subject: [PATCH 1/8] fpu/init: Get rid of two redundant clts() calls

CR0.TS is cleared by a direct CR0 write in fpu__init_cpu_generic().
We don't need to call clts() two more times right after that.

Signed-off-by: Andy Lutomirski <luto@...nel.org>
---
 arch/x86/kernel/fpu/init.c | 18 ------------------
 1 file changed, 18 deletions(-)

diff --git a/arch/x86/kernel/fpu/init.c b/arch/x86/kernel/fpu/init.c
index 1a09d133c801..60dece392b3a 100644
--- a/arch/x86/kernel/fpu/init.c
+++ b/arch/x86/kernel/fpu/init.c
@@ -10,15 +10,6 @@
 #include <linux/init.h>
 
 /*
- * Initialize the TS bit in CR0 according to the style of context-switches
- * we are using:
- */
-static void fpu__init_cpu_ctx_switch(void)
-{
-	clts();
-}
-
-/*
  * Initialize the registers found in all CPUs, CR0 and CR4:
  */
 static void fpu__init_cpu_generic(void)
@@ -55,7 +46,6 @@ void fpu__init_cpu(void)
 {
 	fpu__init_cpu_generic();
 	fpu__init_cpu_xstate();
-	fpu__init_cpu_ctx_switch();
 }
 
 /*
@@ -290,14 +280,6 @@ void __init fpu__init_system(struct cpuinfo_x86 *c)
 	 */
 	fpu__init_cpu();
 
-	/*
-	 * But don't leave CR0::TS set yet, as some of the FPU setup
-	 * methods depend on being able to execute FPU instructions
-	 * that will fault on a set TS, such as the FXSAVE in
-	 * fpu__init_system_mxcsr().
-	 */
-	clts();
-
 	fpu__init_system_generic();
 	fpu__init_system_xstate_size_legacy();
 	fpu__init_system_xstate();
-- 
2.7.4