Commit 4f81cbaf authored by yu-cheng yu's avatar yu-cheng yu Committed by Ingo Molnar
Browse files

x86/fpu: Fix early FPU command-line parsing 



The function fpu__init_system() is executed before
parse_early_param(). This causes wrong FPU configuration. This
patch fixes this issue by parsing boot_command_line in the
beginning of fpu__init_system().

With all four patches in this series, each parameter disables
features as the following:

eagerfpu=off: eagerfpu, avx, avx2, avx512, mpx
no387: fpu
nofxsr: fxsr, fxsropt, xmm
noxsave: xsave, xsaveopt, xsaves, xsavec, avx, avx2, avx512,
mpx, xgetbv1 noxsaveopt: xsaveopt
noxsaves: xsaves

Signed-off-by: default avatarYu-cheng Yu <yu-cheng.yu@intel.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Borislav Petkov <bp@suse.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Quentin Casasnovas <quentin.casasnovas@oracle.com>
Cc: Ravi V. Shankar <ravi.v.shankar@intel.com>
Cc: Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: yu-cheng yu <yu-cheng.yu@intel.com>
Link: http://lkml.kernel.org/r/1452119094-7252-2-git-send-email-yu-cheng.yu@intel.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent b500f77b

arch/x86/kernel/fpu/init.c

+38 −71
Original line number Diff line number Diff line
@@ -3,8 +3,11 @@ 
 */

#include <asm/fpu/internal.h>

#include <asm/tlbflush.h>

#include <asm/setup.h>

#include <asm/cmdline.h>



#include <linux/sched.h>

#include <linux/init.h>



/*

 * Initialize the TS bit in CR0 according to the style of context-switches
@@ -270,18 +273,6 @@ static void __init fpu__init_system_xstate_size_legacy(void) 
 */

static enum { AUTO, ENABLE, DISABLE } eagerfpu = AUTO;



static int __init eager_fpu_setup(char *s)

{

	if (!strcmp(s, "on"))

		eagerfpu = ENABLE;

	else if (!strcmp(s, "off"))

		eagerfpu = DISABLE;

	else if (!strcmp(s, "auto"))

		eagerfpu = AUTO;

	return 1;

}

__setup("eagerfpu=", eager_fpu_setup);



/*

 * Pick the FPU context switching strategy:

 */
@@ -315,12 +306,47 @@ static void __init fpu__init_system_ctx_switch(void) 
	printk(KERN_INFO "x86/fpu: Using '%s' FPU context switches.\n", eagerfpu == ENABLE ? "eager" : "lazy");

}



/*

 * We parse fpu parameters early because fpu__init_system() is executed

 * before parse_early_param().

 */

static void __init fpu__init_parse_early_param(void)

{

	/*

	 * No need to check "eagerfpu=auto" again, since it is the

	 * initial default.

	 */

	if (cmdline_find_option_bool(boot_command_line, "eagerfpu=off"))

		eagerfpu = DISABLE;

	else if (cmdline_find_option_bool(boot_command_line, "eagerfpu=on"))

		eagerfpu = ENABLE;



	if (cmdline_find_option_bool(boot_command_line, "no387"))

		setup_clear_cpu_cap(X86_FEATURE_FPU);



	if (cmdline_find_option_bool(boot_command_line, "nofxsr")) {

		setup_clear_cpu_cap(X86_FEATURE_FXSR);

		setup_clear_cpu_cap(X86_FEATURE_FXSR_OPT);

		setup_clear_cpu_cap(X86_FEATURE_XMM);

	}



	if (cmdline_find_option_bool(boot_command_line, "noxsave"))

		fpu__xstate_clear_all_cpu_caps();



	if (cmdline_find_option_bool(boot_command_line, "noxsaveopt"))

		setup_clear_cpu_cap(X86_FEATURE_XSAVEOPT);



	if (cmdline_find_option_bool(boot_command_line, "noxsaves"))

		setup_clear_cpu_cap(X86_FEATURE_XSAVES);

}



/*

 * Called on the boot CPU once per system bootup, to set up the initial

 * FPU state that is later cloned into all processes:

 */

void __init fpu__init_system(struct cpuinfo_x86 *c)

{

	fpu__init_parse_early_param();

	fpu__init_system_early_generic(c);



	/*
@@ -344,62 +370,3 @@ void __init fpu__init_system(struct cpuinfo_x86 *c) 


	fpu__init_system_ctx_switch();

}
 


/*

 * Boot parameter to turn off FPU support and fall back to math-emu:

 */

static int __init no_387(char *s)

{

	setup_clear_cpu_cap(X86_FEATURE_FPU);

	return 1;

}

__setup("no387", no_387);



/*

 * Disable all xstate CPU features:

 */

static int __init x86_noxsave_setup(char *s)

{

	if (strlen(s))

		return 0;



	fpu__xstate_clear_all_cpu_caps();



	return 1;

}

__setup("noxsave", x86_noxsave_setup);



/*

 * Disable the XSAVEOPT instruction specifically:

 */

static int __init x86_noxsaveopt_setup(char *s)

{

	setup_clear_cpu_cap(X86_FEATURE_XSAVEOPT);



	return 1;

}

__setup("noxsaveopt", x86_noxsaveopt_setup);



/*

 * Disable the XSAVES instruction:

 */

static int __init x86_noxsaves_setup(char *s)

{

	setup_clear_cpu_cap(X86_FEATURE_XSAVES);



	return 1;

}

__setup("noxsaves", x86_noxsaves_setup);



/*

 * Disable FX save/restore and SSE support:

 */

static int __init x86_nofxsr_setup(char *s)

{

	setup_clear_cpu_cap(X86_FEATURE_FXSR);

	setup_clear_cpu_cap(X86_FEATURE_FXSR_OPT);

	setup_clear_cpu_cap(X86_FEATURE_XMM);



	return 1;

}

__setup("nofxsr", x86_nofxsr_setup);

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