Patch "x86/fpu: Parse clearcpuid= as early XSAVE argument" has been added to the 4.14-stable tree

This is a note to let you know that I've just added the patch titled

x86/fpu: Parse clearcpuid= as early XSAVE argument

to the 4.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
x86-fpu-parse-clearcpuid-as-early-xsave-argument.patch
and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Andi Kleen <[email protected]>
Date: Fri, 13 Oct 2017 14:56:43 -0700
Subject: x86/fpu: Parse clearcpuid= as early XSAVE argument

From: Andi Kleen <[email protected]>

commit 0c2a3913d6f50503f7c59d83a6219e39508cc898 upstream.

With a followon patch we want to make clearcpuid affect the XSAVE configuration. But xsave is currently initialized before arguments are parsed. Move the clearcpuid= parsing into the special early xsave argument parsing code.

Since clearcpuid= contains a = we need to keep the old __setup around as a dummy, otherwise it would end up as a environment variable in init's environment.

---
 arch/x86/kernel/cpu/common.c |   16 +++++++---------
 arch/x86/kernel/fpu/init.c   |   11 +++++++++++
 2 files changed, 18 insertions(+), 9 deletions(-)

@@ -1301,18 +1301,16 @@ void print_cpu_info(struct cpuinfo_x86 *
 		pr_cont(")\n");
 }
 
-static __init int setup_disablecpuid(char *arg)
+/*
+ * clearcpuid= was already parsed in fpu__init_parse_early_param.
+ * But we need to keep a dummy __setup around otherwise it would
+ * show up as an environment variable for init.
+ */
+static __init int setup_clearcpuid(char *arg)
 {
-	int bit;
-
-	if (get_option(&arg, &bit) && bit >= 0 && bit < NCAPINTS * 32)
-		setup_clear_cpu_cap(bit);
-	else
-		return 0;
-
 	return 1;
 }
-__setup("clearcpuid=", setup_disablecpuid);
+__setup("clearcpuid=", setup_clearcpuid);
 
 #ifdef CONFIG_X86_64
 DEFINE_PER_CPU_FIRST(union irq_stack_union,

@@ -249,6 +249,10 @@ static void __init fpu__init_system_ctx_
  */
 static void __init fpu__init_parse_early_param(void)
 {
+	char arg[32];
+	char *argptr = arg;
+	int bit;
+
 	if (cmdline_find_option_bool(boot_command_line, "no387"))
 		setup_clear_cpu_cap(X86_FEATURE_FPU);
 

@@ -266,6 +270,13 @@ static void __init fpu__init_parse_early
 
 	if (cmdline_find_option_bool(boot_command_line, "noxsaves"))
 		setup_clear_cpu_cap(X86_FEATURE_XSAVES);
+
+	if (cmdline_find_option(boot_command_line, "clearcpuid", arg,
+				sizeof(arg)) &&
+	    get_option(&argptr, &bit) &&
+	    bit >= 0 &&
+	    bit < NCAPINTS * 32)
+		setup_clear_cpu_cap(bit);
 }
 
 /*

Patches currently in stable-queue which might be from [email protected] are

queue-4.14/bitops-add-clear-set_bit32-to-linux-bitops.h.patch queue-4.14/x86-fpu-remove-the-explicit-clearing-of-xsave-dependent-features.patch queue-4.14/x86-cpuid-add-generic-table-for-cpuid-dependencies.patch queue-4.14/x86-cpuid-prevent-out-of-bound-access-in-do_clear_cpu_cap.patch queue-4.14/x86-fpu-parse-clearcpuid-as-early-xsave-argument.patch queue-4.14/x86-fpu-make-xsave-check-the-base-cpuid-features-before-enabling.patch