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Subject[tip:x86/fpu] x86/fpu: Parse clearcpuid= as early XSAVE argument
Commit-ID:  0c2a3913d6f50503f7c59d83a6219e39508cc898
Gitweb: https://git.kernel.org/tip/0c2a3913d6f50503f7c59d83a6219e39508cc898
Author: Andi Kleen <ak@linux.intel.com>
AuthorDate: Fri, 13 Oct 2017 14:56:43 -0700
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Tue, 17 Oct 2017 17:14:57 +0200

x86/fpu: Parse clearcpuid= as early XSAVE argument

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.

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20171013215645.23166-4-andi@firstfloor.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
arch/x86/kernel/cpu/common.c | 16 +++++++---------
arch/x86/kernel/fpu/init.c | 11 +++++++++++
2 files changed, 18 insertions(+), 9 deletions(-)

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index c9176ba..03bb004 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1301,18 +1301,16 @@ void print_cpu_info(struct cpuinfo_x86 *c)
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,
diff --git a/arch/x86/kernel/fpu/init.c b/arch/x86/kernel/fpu/init.c
index 7affb7e..6abd835 100644
--- a/arch/x86/kernel/fpu/init.c
+++ b/arch/x86/kernel/fpu/init.c
@@ -249,6 +249,10 @@ static void __init fpu__init_system_ctx_switch(void)
*/
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_param(void)

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);
}

/*
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