[RFC PATCH] x86/boot: Initialize FPU and X86_FEATURE_ALWAYS even if we don't have CPUID

[RFC PATCH] x86/boot: Initialize FPU and X86_FEATURE_ALWAYS even if we don't have CPUID

[Andy Lutomirski]

Otherwise arch_task_struct_size == 0 and we die.  While we're at it,
set X86_FEATURE_ALWAYS, too.

Cc: stable@vger.kernel.org
Cc: Dave Hansen <dave@sr71.net>
Cc: Ingo Molnar <mingo@kernel.org>
Fixes: aaeb5c01c5b ("x86/fpu, sched: Introduce CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT and use it on x86")
Reported-by: david@saggiorato.net
Signed-off-by: Andy Lutomirski <luto@kernel.org>
---

Totally untested except by the 0-day bot, since I don't have an
affected machine and QEMU can't emulate anything without CPUID.

 arch/x86/kernel/cpu/common.c | 23 +++++++++++------------
 1 file changed, 11 insertions(+), 12 deletions(-)

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 809eda03c527..bcc9ccc220c9 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -804,21 +804,20 @@ static void __init early_identify_cpu(struct cpuinfo_x86 *c)
 		identify_cpu_without_cpuid(c);
 
 	/* cyrix could have cpuid enabled via c_identify()*/
-	if (!have_cpuid_p())
-		return;
+	if (have_cpuid_p()) {
+		cpu_detect(c);
+		get_cpu_vendor(c);
+		get_cpu_cap(c);
 
-	cpu_detect(c);
-	get_cpu_vendor(c);
-	get_cpu_cap(c);
-
-	if (this_cpu->c_early_init)
-		this_cpu->c_early_init(c);
+		if (this_cpu->c_early_init)
+			this_cpu->c_early_init(c);
 
-	c->cpu_index = 0;
-	filter_cpuid_features(c, false);
+		c->cpu_index = 0;
+		filter_cpuid_features(c, false);
 
-	if (this_cpu->c_bsp_init)
-		this_cpu->c_bsp_init(c);
+		if (this_cpu->c_bsp_init)
+			this_cpu->c_bsp_init(c);
+	}
 
 	setup_force_cpu_cap(X86_FEATURE_ALWAYS);
 	fpu__init_system(c);
-- 
2.7.4

Re: [RFC PATCH] x86/boot: Initialize FPU and X86_FEATURE_ALWAYS even if we don't have CPUID

[David Saggiorato]

[-- Attachment #1: Type: text/plain, Size: 1891 bytes --]

Tested-by: David Saggiorato <david@saggiorato.net>Le mercredi 28 septembre 2016 à 16:06 -0700, Andy Lutomirski a écrit :
> Otherwise arch_task_struct_size == 0 and we die.  While we're at it,
> set X86_FEATURE_ALWAYS, too.
> 
> Cc: stable@vger.kernel.org
> Cc: Dave Hansen <dave@sr71.net>
> Cc: Ingo Molnar <mingo@kernel.org>
> Fixes: aaeb5c01c5b ("x86/fpu, sched: Introduce
> CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT and use it on x86")
> Reported-by: david@saggiorato.net
> Signed-off-by: Andy Lutomirski <luto@kernel.org>
> ---
> 
> Totally untested except by the 0-day bot, since I don't have an
> affected machine and QEMU can't emulate anything without CPUID.
> 
>  arch/x86/kernel/cpu/common.c | 23 +++++++++++------------
>  1 file changed, 11 insertions(+), 12 deletions(-)
> 
> diff --git a/arch/x86/kernel/cpu/common.c
> b/arch/x86/kernel/cpu/common.c
> index 809eda03c527..bcc9ccc220c9 100644
> --- a/arch/x86/kernel/cpu/common.c
> +++ b/arch/x86/kernel/cpu/common.c
> @@ -804,21 +804,20 @@ static void __init early_identify_cpu(struct
> cpuinfo_x86 *c)
>  		identify_cpu_without_cpuid(c);
>  
>  	/* cyrix could have cpuid enabled via c_identify()*/
> -	if (!have_cpuid_p())
> -		return;
> +	if (have_cpuid_p()) {
> +		cpu_detect(c);
> +		get_cpu_vendor(c);
> +		get_cpu_cap(c);
>  
> -	cpu_detect(c);
> -	get_cpu_vendor(c);
> -	get_cpu_cap(c);
> -
> -	if (this_cpu->c_early_init)
> -		this_cpu->c_early_init(c);
> +		if (this_cpu->c_early_init)
> +			this_cpu->c_early_init(c);
>  
> -	c->cpu_index = 0;
> -	filter_cpuid_features(c, false);
> +		c->cpu_index = 0;
> +		filter_cpuid_features(c, false);
>  
> -	if (this_cpu->c_bsp_init)
> -		this_cpu->c_bsp_init(c);
> +		if (this_cpu->c_bsp_init)
> +			this_cpu->c_bsp_init(c);
> +	}
>  
>  	setup_force_cpu_cap(X86_FEATURE_ALWAYS);
>  	fpu__init_system(c);

[-- Attachment #2: This is a digitally signed message part --]
[-- Type: application/pgp-signature, Size: 859 bytes --]

[tip:x86/urgent] x86/boot: Initialize FPU and X86_FEATURE_ALWAYS even if we don't have CPUID

[tip-bot for Andy Lutomirski]

Commit-ID:  05fb3c199bb09f5b85de56cc3ede194ac95c5e1f
Gitweb:     http://git.kernel.org/tip/05fb3c199bb09f5b85de56cc3ede194ac95c5e1f
Author:     Andy Lutomirski <luto@kernel.org>
AuthorDate: Wed, 28 Sep 2016 16:06:33 -0700
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Fri, 30 Sep 2016 13:53:04 +0200

x86/boot: Initialize FPU and X86_FEATURE_ALWAYS even if we don't have CPUID

Otherwise arch_task_struct_size == 0 and we die.  While we're at it,
set X86_FEATURE_ALWAYS, too.

Reported-by: David Saggiorato <david@saggiorato.net>
Tested-by: David Saggiorato <david@saggiorato.net>
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave@sr71.net>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Fixes: aaeb5c01c5b ("x86/fpu, sched: Introduce CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT and use it on x86")
Link: http://lkml.kernel.org/r/8de723afbf0811071185039f9088733188b606c9.1475103911.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 arch/x86/kernel/cpu/common.c | 23 +++++++++++------------
 1 file changed, 11 insertions(+), 12 deletions(-)

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 809eda0..bcc9ccc 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -804,21 +804,20 @@ static void __init early_identify_cpu(struct cpuinfo_x86 *c)
 		identify_cpu_without_cpuid(c);
 
 	/* cyrix could have cpuid enabled via c_identify()*/
-	if (!have_cpuid_p())
-		return;
+	if (have_cpuid_p()) {
+		cpu_detect(c);
+		get_cpu_vendor(c);
+		get_cpu_cap(c);
 
-	cpu_detect(c);
-	get_cpu_vendor(c);
-	get_cpu_cap(c);
-
-	if (this_cpu->c_early_init)
-		this_cpu->c_early_init(c);
+		if (this_cpu->c_early_init)
+			this_cpu->c_early_init(c);
 
-	c->cpu_index = 0;
-	filter_cpuid_features(c, false);
+		c->cpu_index = 0;
+		filter_cpuid_features(c, false);
 
-	if (this_cpu->c_bsp_init)
-		this_cpu->c_bsp_init(c);
+		if (this_cpu->c_bsp_init)
+			this_cpu->c_bsp_init(c);
+	}
 
 	setup_force_cpu_cap(X86_FEATURE_ALWAYS);
 	fpu__init_system(c);

Re: [tip:x86/urgent] x86/boot: Initialize FPU and X86_FEATURE_ALWAYS even if we don't have CPUID

[Borislav Petkov]

On Fri, Sep 30, 2016 at 05:06:46AM -0700, tip-bot for Andy Lutomirski wrote:
> Commit-ID:  05fb3c199bb09f5b85de56cc3ede194ac95c5e1f
> Gitweb:     http://git.kernel.org/tip/05fb3c199bb09f5b85de56cc3ede194ac95c5e1f
> Author:     Andy Lutomirski <luto@kernel.org>
> AuthorDate: Wed, 28 Sep 2016 16:06:33 -0700
> Committer:  Ingo Molnar <mingo@kernel.org>
> CommitDate: Fri, 30 Sep 2016 13:53:04 +0200
> 
> x86/boot: Initialize FPU and X86_FEATURE_ALWAYS even if we don't have CPUID
> 
> Otherwise arch_task_struct_size == 0 and we die.  While we're at it,
> set X86_FEATURE_ALWAYS, too.

...

> diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
> index 809eda0..bcc9ccc 100644
> --- a/arch/x86/kernel/cpu/common.c
> +++ b/arch/x86/kernel/cpu/common.c
> @@ -804,21 +804,20 @@ static void __init early_identify_cpu(struct cpuinfo_x86 *c)
>  		identify_cpu_without_cpuid(c);
>  
>  	/* cyrix could have cpuid enabled via c_identify()*/
> -	if (!have_cpuid_p())
> -		return;
> +	if (have_cpuid_p()) {

Let's make it even simpler:

---
From: Borislav Petkov <bp@suse.de>
Date: Fri, 30 Sep 2016 17:08:10 +0200
Subject: [PATCH] x86/boot: Streamline CPUID check conditional

We have now:

	if (!have_cpuid_p())
		...

	if (have_cpuid_p())
		...

Turn it into a good, ole if-else conditional which is much more
readable.

No functionality change.

Signed-off-by: Borislav Petkov <bp@suse.de>
---
 arch/x86/kernel/cpu/common.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 9bd910a7dd0a..0a6fa6174ed8 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -800,9 +800,6 @@ static void __init early_identify_cpu(struct cpuinfo_x86 *c)
 	memset(&c->x86_capability, 0, sizeof c->x86_capability);
 	c->extended_cpuid_level = 0;
 
-	if (!have_cpuid_p())
-		identify_cpu_without_cpuid(c);
-
 	/* cyrix could have cpuid enabled via c_identify()*/
 	if (have_cpuid_p()) {
 		cpu_detect(c);
@@ -817,6 +814,8 @@ static void __init early_identify_cpu(struct cpuinfo_x86 *c)
 
 		if (this_cpu->c_bsp_init)
 			this_cpu->c_bsp_init(c);
+	} else {
+		identify_cpu_without_cpuid(c);
 	}
 
 	setup_force_cpu_cap(X86_FEATURE_ALWAYS);
-- 
2.8.4

-- 
Regards/Gruss,
    Boris.

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