x86/fpu: FPU init code bugfixes

PATCH In review yu-cheng yu 4 participants 13 messages Jan 6, 2016 – Jan 15, 2016 x86

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yu-cheng yu

author

2016-01-06 22:31 UTC #0 lore raw

cover x86/fpu: FPU init code bugfixes

The function fpu__init_system() is executed before parse_early_param(). This causes wrong fpu configuration. In addition, there are three related issues:

1. XGETBV1 is enabled when noxsave is given
2. MPX is enabled when eagerfpu=off is given
3. AVX is enabled when eagerfpu=off is given

Issues 1 and 3 are existing bugs. Issue 2 is a fallout from the command-line parsing move.

The following four patches fix these issues.

yu-cheng yu (4):
x86/fpu: Fix early fpu command-line parsing.
x86/fpu: Disable XGETBV1 when no XSAVE.
x86/fpu: Disable MPX when eagerfpu is off.
x86/fpu: Disable AVX when eagerfpu is off.

 arch/x86/include/asm/fpu/internal.h |   1 +
 arch/x86/include/asm/fpu/xstate.h   |  11 +--
 arch/x86/kernel/fpu/init.c          | 161 +++++++++++++++++++-----------------
 arch/x86/kernel/fpu/xstate.c        |   4 +-
 4 files changed, 92 insertions(+), 85 deletions(-)

Signed-off-by Yu-cheng Yu <[email protected]>

Cc [email protected]

Cc H. Peter Anvin <[email protected]>

Cc Thomas Gleixner <[email protected]>

Cc Dave Hansen <[email protected]>

Cc Ingo Molnar <[email protected]>

Cc Borislav Petkov <[email protected]>

Cc Sai Praneeth Prakhya <[email protected]>

Cc Ravi V. Shankar <[email protected]>

Cc Fenghua Yu <[email protected]>

Signature · 1 line

1.9.1

yu-cheng yu

author

2016-01-06 22:32 UTC #1 lore raw

PATCH 1/4 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 Yu-cheng Yu <[email protected]>

Cc [email protected]

Cc H. Peter Anvin <[email protected]>

Cc Thomas Gleixner <[email protected]>

Cc Dave Hansen <[email protected]>

Cc Ingo Molnar <[email protected]>

Cc Borislav Petkov <[email protected]>

Cc Sai Praneeth Prakhya <[email protected]>

Cc Ravi V. Shankar <[email protected]>

Cc Fenghua Yu <[email protected]>

---
 arch/x86/kernel/fpu/init.c | 109 ++++++++++++++++-----------------------------
 1 file changed, 38 insertions(+), 71 deletions(-)

arch/x86/kernel/fpu/init.c +38 ~~-71~~

index be39b5f..057b73e 100644
@@ -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

@@ -261,18 +264,6 @@ 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:
  */

@@ -307,11 +298,46 @@ static void __init fpu__init_system_ctx_switch(void)
 }
 
 /*
+ * 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);
 
 	/*

@@ -335,62 +361,3 @@ 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);

Signature · 1 line

1.9.1

tip-bot for yu-cheng yu

merge bot

2016-01-12 12:02 UTC #2 lore raw

[tip:x86/asm] x86/fpu: Fix early FPU command-line parsing

x86/fpu: Fix early FPU command-line parsing

Commit-ID:  4f81cbafcce2c603db7865e9d0e461f7947d77d4
Gitweb:     http://git.kernel.org/tip/4f81cbafcce2c603db7865e9d0e461f7947d77d4
Author:     yu-cheng yu <[email protected]>
AuthorDate: Wed, 6 Jan 2016 14:24:51 -0800
Committer:  Ingo Molnar <[email protected]>
CommitDate: Tue, 12 Jan 2016 11:51:20 +0100

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 Yu-cheng Yu <[email protected]>

Cc Andy Lutomirski <[email protected]>

Cc Borislav Petkov <[email protected]>

Cc Dave Hansen <[email protected]>

Cc Fenghua Yu <[email protected]>

Cc H. Peter Anvin <[email protected]>

Cc Linus Torvalds <[email protected]>

Cc Oleg Nesterov <[email protected]>

Cc Peter Zijlstra <[email protected]>

Cc Quentin Casasnovas <[email protected]>

Cc Ravi V. Shankar <[email protected]>

Cc Sai Praneeth Prakhya <[email protected]>

Cc Thomas Gleixner <[email protected]>

Cc yu-cheng yu <[email protected]>

Link http://lkml.kernel.org/r/[email protected] open here

Signed-off-by Ingo Molnar <[email protected]>

---
 arch/x86/kernel/fpu/init.c | 109 ++++++++++++++++-----------------------------
 1 file changed, 38 insertions(+), 71 deletions(-)

arch/x86/kernel/fpu/init.c +38 ~~-71~~

index 7b2978a..3a45fcd 100644
@@ -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:
  */

@@ -316,11 +307,46 @@ static void __init fpu__init_system_ctx_switch(void)
 }
 
 /*
+ * 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);

Borislav Petkov

maintainer

2016-01-15 20:29 UTC #3 lore raw

Re: [tip:x86/asm] x86/fpu: Fix early FPU command-line parsing

Quoted 44 lines · tip-bot for yu-cheng yu

Commit-ID:  4f81cbafcce2c603db7865e9d0e461f7947d77d4
Gitweb:     http://git.kernel.org/tip/4f81cbafcce2c603db7865e9d0e461f7947d77d4
Author:     yu-cheng yu <[email protected]>
AuthorDate: Wed, 6 Jan 2016 14:24:51 -0800
Committer:  Ingo Molnar <[email protected]>
CommitDate: Tue, 12 Jan 2016 11:51:20 +0100
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 Yu-cheng Yu <[email protected]>
Cc Andy Lutomirski <[email protected]>
Cc Borislav Petkov <[email protected]>
Cc Borislav Petkov <[email protected]>
Cc Dave Hansen <[email protected]>
Cc Fenghua Yu <[email protected]>
Cc H. Peter Anvin <[email protected]>
Cc Linus Torvalds <[email protected]>
Cc Oleg Nesterov <[email protected]>
Cc Peter Zijlstra <[email protected]>
Cc Quentin Casasnovas <[email protected]>
Cc Ravi V. Shankar <[email protected]>
Cc Sai Praneeth Prakhya <[email protected]>
Cc Thomas Gleixner <[email protected]>
Cc yu-cheng yu <[email protected]>
Link http://lkml.kernel.org/r/[email protected] open here
Signed-off-by Ingo Molnar <[email protected]>
---
 arch/x86/kernel/fpu/init.c | 109 ++++++++++++++++-----------------------------
1 file changed, 38 insertions(+), 71 deletions(-)

...

Quoted 21 lines

+ * We parse fpu parameters early because fpu__init_system() is executed
+ * before parse_early_param().
+ */

arch/x86/kernel/fpu/init.c +18 -0

+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);

arch/x86/kernel/fpu/init.c static void __init fpu__init_system_ctx_switch(void) · line 340

Quoted 10 lines

arch/x86/kernel/fpu/init.c +10 -0

+	}
+
+	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);

This could certainly be improved: we're iterating over the *whole* command line each time for each option unconditionally instead of iterating word by word and comparing it with all strings.

We'd need something like cmdline_for_each_word() or so, though...

Signature · 4 lines

Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.

Yu-cheng Yu

author

2016-01-15 20:51 UTC #4 lore raw

Re: [tip:x86/asm] x86/fpu: Fix early FPU command-line parsing

Quoted 33 lines · Borislav Petkov

Quoted 18 lines

arch/x86/kernel/fpu/init.c +18 -0

+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);

arch/x86/kernel/fpu/init.c static void __init fpu__init_system_ctx_switch(void) · line 340

Quoted 10 lines

arch/x86/kernel/fpu/init.c +10 -0

+	}
+
+	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);

This could certainly be improved: we're iterating over the *whole* command line each time for each option unconditionally instead of iterating word by word and comparing it with all strings.

Quoted 2 lines

We'd need something like cmdline_for_each_word() or so, though...

That is a good point. I will work on it.

Thanks,
Yu-cheng

Dave Hansen

maintainer

2016-01-15 21:02 UTC #5 lore raw

Re: [tip:x86/asm] x86/fpu: Fix early FPU command-line parsing

Quoted 8 lines · Yu-cheng Yu

Quoted 7 lines
Quoted 7 lines
This could certainly be improved: we're iterating over the *whole* command line each time for each option unconditionally instead of iterating word by word and comparing it with all strings.
We'd need something like cmdline_for_each_word() or so, though...
That is a good point. I will work on it.

I really don't think we need to do this. It's code that runs *ONCE* at boot time. Let's not work on optimizing it unless we have some acute need.

Borislav Petkov

maintainer

2016-01-15 21:09 UTC #6 lore raw

Re: [tip:x86/asm] x86/fpu: Fix early FPU command-line parsing

Quoted 3 lines · Dave Hansen

I really don't think we need to do this. It's code that runs *ONCE* at boot time. Let's not work on optimizing it unless we have some acute need.

It was just a "it would be better if" suggestion, no one said anyone should work on it. And sorry but if we can elegantly optimize something, I think we should always do it.

Signature · 4 lines

Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.

yu-cheng yu

author

2016-01-06 22:32 UTC #7 lore raw

PATCH 2/4 x86/fpu: Disable XGETBV1 when no XSAVE

In reply to yu-cheng yu

When "noxsave" is given as a command-line input, the kernel should disable XGETBV1. This issue currently does not cause any actual problems. XGETBV1 is only useful if we have something using the 'init optimization' (i.e. xsaveopt, xsaves). We already clear both of those in fpu__xstate_clear_all_cpu_caps(). But this is good for completeness.

Signed-off-by Yu-cheng Yu <[email protected]>

Reviewed-by Dave Hansen <[email protected]>

Cc [email protected]

Cc H. Peter Anvin <[email protected]>

Cc Thomas Gleixner <[email protected]>

Cc Dave Hansen <[email protected]>

Cc Ingo Molnar <[email protected]>

Cc Borislav Petkov <[email protected]>

Cc Sai Praneeth Prakhya <[email protected]>

Cc Ravi V. Shankar <[email protected]>

Cc Fenghua Yu <[email protected]>

---
 arch/x86/kernel/fpu/xstate.c | 1 +
 1 file changed, 1 insertion(+)

arch/x86/kernel/fpu/xstate.c +1 -0

index 70fc312..b27d3b6 100644
@@ -52,6 +52,7 @@ void fpu__xstate_clear_all_cpu_caps(void)
 	setup_clear_cpu_cap(X86_FEATURE_AVX512ER);
 	setup_clear_cpu_cap(X86_FEATURE_AVX512CD);
 	setup_clear_cpu_cap(X86_FEATURE_MPX);
+	setup_clear_cpu_cap(X86_FEATURE_XGETBV1);
 }
 
 /*

Signature · 1 line

1.9.1

tip-bot for yu-cheng yu

merge bot

2016-01-12 12:02 UTC #8 lore raw

[tip:x86/asm] x86/fpu: Disable XGETBV1 when no XSAVE

x86/fpu: Disable XGETBV1 when no XSAVE

Commit-ID:  eb7c5f872e697b0aebd846cf3a3328d71e9decb2
Gitweb:     http://git.kernel.org/tip/eb7c5f872e697b0aebd846cf3a3328d71e9decb2
Author:     yu-cheng yu <[email protected]>
AuthorDate: Wed, 6 Jan 2016 14:24:52 -0800
Committer:  Ingo Molnar <[email protected]>
CommitDate: Tue, 12 Jan 2016 11:51:21 +0100

x86/fpu: Disable XGETBV1 when no XSAVE

Signed-off-by Yu-cheng Yu <[email protected]>

Reviewed-by Dave Hansen <[email protected]>

Cc Andy Lutomirski <[email protected]>

Cc Borislav Petkov <[email protected]>

Cc Dave Hansen <[email protected]>

Cc Fenghua Yu <[email protected]>

Cc H. Peter Anvin <[email protected]>

Cc Linus Torvalds <[email protected]>

Cc Oleg Nesterov <[email protected]>

Cc Peter Zijlstra <[email protected]>

Cc Quentin Casasnovas <[email protected]>

Cc Ravi V. Shankar <[email protected]>

Cc Sai Praneeth Prakhya <[email protected]>

Cc Thomas Gleixner <[email protected]>

Cc yu-cheng yu <[email protected]>

Link http://lkml.kernel.org/r/[email protected] open here

Signed-off-by Ingo Molnar <[email protected]>

---
 arch/x86/kernel/fpu/xstate.c | 1 +
 1 file changed, 1 insertion(+)

arch/x86/kernel/fpu/xstate.c +1 -0

index 40f1002..d489f27 100644
@@ -52,6 +52,7 @@ void fpu__xstate_clear_all_cpu_caps(void)
 	setup_clear_cpu_cap(X86_FEATURE_AVX512ER);
 	setup_clear_cpu_cap(X86_FEATURE_AVX512CD);
 	setup_clear_cpu_cap(X86_FEATURE_MPX);
+	setup_clear_cpu_cap(X86_FEATURE_XGETBV1);
 }
 
 /*

yu-cheng yu

author

2016-01-06 22:32 UTC #9 lore raw

PATCH 3/4 x86/fpu: Disable MPX when eagerfpu is off

In reply to yu-cheng yu

This issue is a fallout from the command-line parsing move.

When "eagerfpu=off" is given as a command-line input, the kernel should disable MPX support. The decision for turning off MPX was made in fpu__init_system_ctx_switch(), which is after the selection of the XSAVE format. This patch fixes it by getting that decision done earlier in fpu__init_system_xstate().

Signed-off-by Yu-cheng Yu <[email protected]>

Cc [email protected]

Cc H. Peter Anvin <[email protected]>

Cc Thomas Gleixner <[email protected]>

Cc Dave Hansen <[email protected]>

Cc Ingo Molnar <[email protected]>

Cc Borislav Petkov <[email protected]>

Cc Sai Praneeth Prakhya <[email protected]>

Cc Ravi V. Shankar <[email protected]>

Cc Fenghua Yu <[email protected]>

---
 arch/x86/include/asm/fpu/internal.h |  1 +
 arch/x86/kernel/fpu/init.c          | 56 +++++++++++++++++++++++++++++--------
 arch/x86/kernel/fpu/xstate.c        |  3 +-
 3 files changed, 46 insertions(+), 14 deletions(-)

arch/x86/include/asm/fpu/internal.h +1 -0

index 3c3550c..6b07a842 100644
@@ -42,6 +42,7 @@ extern void fpu__init_cpu_xstate(void);
 extern void fpu__init_system(struct cpuinfo_x86 *c);
 extern void fpu__init_check_bugs(void);
 extern void fpu__resume_cpu(void);
+extern u64 fpu__get_supported_xfeatures_mask(void);
 
 /*
  * Debugging facility:

arch/x86/kernel/fpu/init.c +44 ~~-12~~

80 lines not on this page · raw message

arch/x86/kernel/fpu/xstate.c +1 -2

index b27d3b6..8fb473b 100644
@@ -633,8 +633,7 @@ void __init fpu__init_system_xstate(void)
 		BUG();
 	}
 
-	/* Support only the state known to the OS: */
-	xfeatures_mask = xfeatures_mask & XCNTXT_MASK;
+	xfeatures_mask &= fpu__get_supported_xfeatures_mask();
 
 	/* Enable xstate instructions to be able to continue with initialization: */
 	fpu__init_cpu_xstate();

Signature · 1 line

1.9.1

tip-bot for yu-cheng yu

merge bot

2016-01-12 12:02 UTC #10 lore raw

[tip:x86/asm] x86/fpu: Disable MPX when eagerfpu is off

x86/fpu: Disable MPX when eagerfpu is off

Commit-ID:  a5fe93a549c54838063d2952dd9643b0b18aa67f
Gitweb:     http://git.kernel.org/tip/a5fe93a549c54838063d2952dd9643b0b18aa67f
Author:     yu-cheng yu <[email protected]>
AuthorDate: Wed, 6 Jan 2016 14:24:53 -0800
Committer:  Ingo Molnar <[email protected]>
CommitDate: Tue, 12 Jan 2016 11:51:21 +0100

x86/fpu: Disable MPX when eagerfpu is off

This issue is a fallout from the command-line parsing move.

Signed-off-by Yu-cheng Yu <[email protected]>

Cc Andy Lutomirski <[email protected]>

Cc Borislav Petkov <[email protected]>

Cc Dave Hansen <[email protected]>

Cc Fenghua Yu <[email protected]>

Cc H. Peter Anvin <[email protected]>

Cc Linus Torvalds <[email protected]>

Cc Oleg Nesterov <[email protected]>

Cc Peter Zijlstra <[email protected]>

Cc Quentin Casasnovas <[email protected]>

Cc Ravi V. Shankar <[email protected]>

Cc Sai Praneeth Prakhya <[email protected]>

Cc Thomas Gleixner <[email protected]>

Cc yu-cheng yu <[email protected]>

Link http://lkml.kernel.org/r/[email protected] open here

Signed-off-by Ingo Molnar <[email protected]>

---
 arch/x86/include/asm/fpu/internal.h |  1 +
 arch/x86/kernel/fpu/init.c          | 56 +++++++++++++++++++++++++++++--------
 arch/x86/kernel/fpu/xstate.c        |  3 +-
 3 files changed, 46 insertions(+), 14 deletions(-)

arch/x86/include/asm/fpu/internal.h +1 -0

index eadcdd5..0fd440d 100644
@@ -42,6 +42,7 @@ extern void fpu__init_cpu_xstate(void);
 extern void fpu__init_system(struct cpuinfo_x86 *c);
 extern void fpu__init_check_bugs(void);
 extern void fpu__resume_cpu(void);
+extern u64 fpu__get_supported_xfeatures_mask(void);
 
 /*
  * Debugging facility:

arch/x86/kernel/fpu/init.c +44 ~~-12~~

80 lines not on this page · raw message

arch/x86/kernel/fpu/xstate.c +1 -2

index d489f27..d425cda5 100644
@@ -633,8 +633,7 @@ void __init fpu__init_system_xstate(void)
 		BUG();
 	}
 
-	/* Support only the state known to the OS: */
-	xfeatures_mask = xfeatures_mask & XCNTXT_MASK;
+	xfeatures_mask &= fpu__get_supported_xfeatures_mask();
 
 	/* Enable xstate instructions to be able to continue with initialization: */
 	fpu__init_cpu_xstate();

yu-cheng yu

author

2016-01-06 22:32 UTC #11 lore raw

PATCH 4/4 x86/fpu: Disable AVX when eagerfpu is off

In reply to yu-cheng yu

When "eagerfpu=off" is given as a command-line input, the kernel should disable AVX support.

The Task Switched bit used for lazy context switching does not support AVX. If AVX is enabled without eagerfpu context switching, one task's AVX state could become corrupted or leak to other tasks. This is a bug and has bad security implications.

This only affects systems that have AVX/AVX2/AVX512 and this issue will be found only when one actually uses AVX/AVX2/AVX512 _AND_ does eagerfpu=off.

Referece: Intel Software Developer's Manual Vol. 3A

Sec. 2.5 Control Registers:
TS Task Switched bit (bit 3 of CR0) -- Allows the saving of the x87 FPU/ MMX/SSE/SSE2/SSE3/SSSE3/SSE4 context on a task switch to be delayed until an x87 FPU/MMX/SSE/SSE2/SSE3/SSSE3/SSE4 instruction is actually executed by the new task.

Sec. 13.4.1 Using the TS Flag to Control the Saving of the X87 FPU and SSE State
When the TS flag is set, the processor monitors the instruction stream for x87 FPU, MMX, SSE instructions. When the processor detects one of these instructions, it raises a device-not-available exeception (#NM) prior to executing the instruction.

Signed-off-by Yu-cheng Yu <[email protected]>

Cc [email protected]

Cc H. Peter Anvin <[email protected]>

Cc Thomas Gleixner <[email protected]>

Cc Dave Hansen <[email protected]>

Cc Ingo Molnar <[email protected]>

Cc Borislav Petkov <[email protected]>

Cc Sai Praneeth Prakhya <[email protected]>

Cc Ravi V. Shankar <[email protected]>

Cc Fenghua Yu <[email protected]>

---
 arch/x86/include/asm/fpu/xstate.h | 11 ++++++-----
 arch/x86/kernel/fpu/init.c        |  6 ++++++
 2 files changed, 12 insertions(+), 5 deletions(-)

arch/x86/include/asm/fpu/xstate.h +6 -5

index 3a6c89b..af30fde 100644
@@ -20,15 +20,16 @@
 
 /* Supported features which support lazy state saving */
 #define XFEATURE_MASK_LAZY	(XFEATURE_MASK_FP | \
-				 XFEATURE_MASK_SSE | \
+				 XFEATURE_MASK_SSE)
+
+/* Supported features which require eager state saving */
+#define XFEATURE_MASK_EAGER	(XFEATURE_MASK_BNDREGS | \
+				 XFEATURE_MASK_BNDCSR | \
 				 XFEATURE_MASK_YMM | \
-				 XFEATURE_MASK_OPMASK |	\
+				 XFEATURE_MASK_OPMASK | \
 				 XFEATURE_MASK_ZMM_Hi256 | \
 				 XFEATURE_MASK_Hi16_ZMM)
 
-/* Supported features which require eager state saving */
-#define XFEATURE_MASK_EAGER	(XFEATURE_MASK_BNDREGS | XFEATURE_MASK_BNDCSR)
-
 /* All currently supported features */
 #define XCNTXT_MASK	(XFEATURE_MASK_LAZY | XFEATURE_MASK_EAGER)

arch/x86/kernel/fpu/init.c +6 -0

index aad53cc..e7e3dbfdb 100644
@@ -291,6 +291,12 @@ u64 __init fpu__get_supported_xfeatures_mask(void)
 static void __init fpu__clear_eager_fpu_features(void)
 {
 	setup_clear_cpu_cap(X86_FEATURE_MPX);
+	setup_clear_cpu_cap(X86_FEATURE_AVX);
+	setup_clear_cpu_cap(X86_FEATURE_AVX2);
+	setup_clear_cpu_cap(X86_FEATURE_AVX512F);
+	setup_clear_cpu_cap(X86_FEATURE_AVX512PF);
+	setup_clear_cpu_cap(X86_FEATURE_AVX512ER);
+	setup_clear_cpu_cap(X86_FEATURE_AVX512CD);
 }
 
 /*

Signature · 1 line

1.9.1

tip-bot for yu-cheng yu

merge bot

2016-01-12 12:03 UTC #12 lore raw

[tip:x86/asm] x86/fpu: Disable AVX when eagerfpu is off

x86/fpu: Disable AVX when eagerfpu is off

Commit-ID:  394db20ca240741a08d472173db13d6f6a6e5a28
Gitweb:     http://git.kernel.org/tip/394db20ca240741a08d472173db13d6f6a6e5a28
Author:     yu-cheng yu <[email protected]>
AuthorDate: Wed, 6 Jan 2016 14:24:54 -0800
Committer:  Ingo Molnar <[email protected]>
CommitDate: Tue, 12 Jan 2016 11:51:21 +0100

x86/fpu: Disable AVX when eagerfpu is off

When "eagerfpu=off" is given as a command-line input, the kernel should disable AVX support.

This only affects systems that have AVX/AVX2/AVX512 and this issue will be found only when one actually uses AVX/AVX2/AVX512 _AND_ does eagerfpu=off.

Reference: Intel Software Developer's Manual Vol. 3A

Signed-off-by Yu-cheng Yu <[email protected]>

Cc Andy Lutomirski <[email protected]>

Cc Borislav Petkov <[email protected]>

Cc Dave Hansen <[email protected]>

Cc Fenghua Yu <[email protected]>

Cc H. Peter Anvin <[email protected]>

Cc Linus Torvalds <[email protected]>

Cc Oleg Nesterov <[email protected]>

Cc Peter Zijlstra <[email protected]>

Cc Quentin Casasnovas <[email protected]>

Cc Ravi V. Shankar <[email protected]>

Cc Sai Praneeth Prakhya <[email protected]>

Cc Thomas Gleixner <[email protected]>

Cc yu-cheng yu <[email protected]>

Link http://lkml.kernel.org/r/[email protected] open here

Signed-off-by Ingo Molnar <[email protected]>

---
 arch/x86/include/asm/fpu/xstate.h | 11 ++++++-----
 arch/x86/kernel/fpu/init.c        |  6 ++++++
 2 files changed, 12 insertions(+), 5 deletions(-)

arch/x86/include/asm/fpu/xstate.h +6 -5

index 3a6c89b..af30fde 100644
@@ -20,15 +20,16 @@
 
 /* Supported features which support lazy state saving */
 #define XFEATURE_MASK_LAZY	(XFEATURE_MASK_FP | \
-				 XFEATURE_MASK_SSE | \
+				 XFEATURE_MASK_SSE)
+
+/* Supported features which require eager state saving */
+#define XFEATURE_MASK_EAGER	(XFEATURE_MASK_BNDREGS | \
+				 XFEATURE_MASK_BNDCSR | \
 				 XFEATURE_MASK_YMM | \
-				 XFEATURE_MASK_OPMASK |	\
+				 XFEATURE_MASK_OPMASK | \
 				 XFEATURE_MASK_ZMM_Hi256 | \
 				 XFEATURE_MASK_Hi16_ZMM)
 
-/* Supported features which require eager state saving */
-#define XFEATURE_MASK_EAGER	(XFEATURE_MASK_BNDREGS | XFEATURE_MASK_BNDCSR)
-
 /* All currently supported features */
 #define XCNTXT_MASK	(XFEATURE_MASK_LAZY | XFEATURE_MASK_EAGER)

arch/x86/kernel/fpu/init.c +6 -0

index f0ab368..6d9f0a7 100644
@@ -300,6 +300,12 @@ u64 __init fpu__get_supported_xfeatures_mask(void)
 static void __init fpu__clear_eager_fpu_features(void)
 {
 	setup_clear_cpu_cap(X86_FEATURE_MPX);
+	setup_clear_cpu_cap(X86_FEATURE_AVX);
+	setup_clear_cpu_cap(X86_FEATURE_AVX2);
+	setup_clear_cpu_cap(X86_FEATURE_AVX512F);
+	setup_clear_cpu_cap(X86_FEATURE_AVX512PF);
+	setup_clear_cpu_cap(X86_FEATURE_AVX512ER);
+	setup_clear_cpu_cap(X86_FEATURE_AVX512CD);
 }
 
 /*