Support generic disabling of all XSAVE features

Support generic disabling of all XSAVE features

[Andi Kleen]

For performance testing and debugging it can be useful to disable XSAVE
features individually. This patchkit hooks up XSAVE with the
generic clearcpuid=... option, so that disabling a CPUID feature
automatically disables the respective XSAVE feature.

It also cleans up CPUID dependency management. Currently it's
possible to generate configurations with cleacpuid that crash.

It replaces an earlier patchkit that did this with special
case options.

v1:
Initial post
v2:
Work around broken lguest by exporting set_cpu_cap
Repost with cover letter
v3:
Repost. No changes to code.
v4:
Rebase to latest tree. Repost.

[PATCH v4 1/5] x86/xsave: Move xsave initialization to after parsing early parameters

[Andi Kleen]

From: Andi Kleen <ak@linux.intel.com>

Move the XSAVE initialization code to be after parsing early parameters.
I don't see any reason why the FPU code needs to be initialized that
early, nothing else in the initialization phase uses XSAVE.
This is useful to be able to handle command line parameters in the
XSAVE initialization code.

Signed-off-by: Andi Kleen <ak@linux.intel.com>
---
 arch/x86/kernel/cpu/common.c | 1 -
 arch/x86/kernel/setup.c      | 3 +++
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index c8b39870f33e..60b7aa6330ed 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -885,7 +885,6 @@ static void __init early_identify_cpu(struct cpuinfo_x86 *c)
 	}
 
 	setup_force_cpu_cap(X86_FEATURE_ALWAYS);
-	fpu__init_system(c);
 }
 
 void __init early_cpu_init(void)
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 3486d0498800..2fba421d6b07 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -91,6 +91,7 @@
 #include <asm/processor.h>
 #include <asm/bugs.h>
 #include <asm/kasan.h>
+#include <asm/fpu/internal.h>
 
 #include <asm/vsyscall.h>
 #include <asm/cpu.h>
@@ -982,6 +983,8 @@ void __init setup_arch(char **cmdline_p)
 
 	parse_early_param();
 
+	fpu__init_system(&boot_cpu_data);
+
 #ifdef CONFIG_MEMORY_HOTPLUG
 	/*
 	 * Memory used by the kernel cannot be hot-removed because Linux
-- 
2.9.4

[PATCH v4 2/5] x86/cpuid: Add generic table for cpuid dependencies

[Andi Kleen]

From: Andi Kleen <ak@linux.intel.com>

Some CPUID features depend on other features. Currently it's
possible to to clear dependent features, but not clear the base features,
which can cause various interesting problems.

This patch implements a generic table to describe dependencies
between CPUID features, to be used by all code that clears
CPUID.

Some subsystems (like XSAVE) had an own implementation of this,
but it's better to do it all in a single place for everyone.

Then clear_cpu_cap and setup_clear_cpu_cap always look up
this table and clear all dependencies too.

This is intended to be a practical table: only for features
that make sense to clear. If someone for example clears FPU,
or other features that are essentially part of the required
base feature set, not much is going to work. Handling
that is right now out of scope. We're only handling
features which can be usefully cleared.

v2: Add EXPORT_SYMBOL for clear_cpu_id for lguest
Signed-off-by: Andi Kleen <ak@linux.intel.com>
---
 arch/x86/include/asm/cpufeature.h  |  8 +++-
 arch/x86/include/asm/cpufeatures.h |  5 +++
 arch/x86/kernel/cpu/Makefile       |  1 +
 arch/x86/kernel/cpu/cpuid-deps.c   | 92 ++++++++++++++++++++++++++++++++++++++
 4 files changed, 104 insertions(+), 2 deletions(-)
 create mode 100644 arch/x86/kernel/cpu/cpuid-deps.c

diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h
index d59c15c3defd..e6145f383ff8 100644
--- a/arch/x86/include/asm/cpufeature.h
+++ b/arch/x86/include/asm/cpufeature.h
@@ -125,8 +125,12 @@ extern const char * const x86_bug_flags[NBUGINTS*32];
 #define boot_cpu_has(bit)	cpu_has(&boot_cpu_data, bit)
 
 #define set_cpu_cap(c, bit)	set_bit(bit, (unsigned long *)((c)->x86_capability))
-#define clear_cpu_cap(c, bit)	clear_bit(bit, (unsigned long *)((c)->x86_capability))
-#define setup_clear_cpu_cap(bit) do { \
+#define __clear_cpu_cap(c, bit)	clear_bit(bit, (unsigned long *)((c)->x86_capability))
+
+extern void setup_clear_cpu_cap(int bit);
+extern void clear_cpu_cap(struct cpuinfo_x86 *cpu, int bit);
+
+#define __setup_clear_cpu_cap(bit) do { \
 	clear_cpu_cap(&boot_cpu_data, bit);	\
 	set_bit(bit, (unsigned long *)cpu_caps_cleared); \
 } while (0)
diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
index ca3c48c0872f..3467e5dd5259 100644
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -21,6 +21,11 @@
  * this feature bit is not displayed in /proc/cpuinfo at all.
  */
 
+/*
+ * When adding new features here that depend on other features,
+ * please update the table in kernel/cpu/cpuid-deps.c
+ */
+
 /* Intel-defined CPU features, CPUID level 0x00000001 (edx), word 0 */
 #define X86_FEATURE_FPU		( 0*32+ 0) /* Onboard FPU */
 #define X86_FEATURE_VME		( 0*32+ 1) /* Virtual Mode Extensions */
diff --git a/arch/x86/kernel/cpu/Makefile b/arch/x86/kernel/cpu/Makefile
index cdf82492b770..ffc3ec870f1e 100644
--- a/arch/x86/kernel/cpu/Makefile
+++ b/arch/x86/kernel/cpu/Makefile
@@ -22,6 +22,7 @@ obj-y			+= rdrand.o
 obj-y			+= match.o
 obj-y			+= bugs.o
 obj-$(CONFIG_CPU_FREQ)	+= aperfmperf.o
+obj-y			+= cpuid-deps.o
 
 obj-$(CONFIG_PROC_FS)	+= proc.o
 obj-$(CONFIG_X86_FEATURE_NAMES) += capflags.o powerflags.o
diff --git a/arch/x86/kernel/cpu/cpuid-deps.c b/arch/x86/kernel/cpu/cpuid-deps.c
new file mode 100644
index 000000000000..08aff02cf2ff
--- /dev/null
+++ b/arch/x86/kernel/cpu/cpuid-deps.c
@@ -0,0 +1,92 @@
+/* Declare dependencies between CPUIDs */
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <asm/cpufeature.h>
+
+struct cpuid_dep {
+	int feature;
+	int dep;
+};
+
+/*
+ * Table of CPUID features that depend on others.
+ *
+ * This only includes dependencies that can be usefully disabled, not
+ * features part of the base set (like FPU).
+ */
+const static struct cpuid_dep cpuid_deps[] = {
+	{ X86_FEATURE_XSAVE,   X86_FEATURE_XSAVEOPT },
+	{ X86_FEATURE_XSAVE,   X86_FEATURE_XSAVEC },
+	{ X86_FEATURE_XSAVE,   X86_FEATURE_XSAVES },
+	{ X86_FEATURE_XSAVE,   X86_FEATURE_AVX },
+	{ X86_FEATURE_XSAVE,   X86_FEATURE_AVX512F },
+	{ X86_FEATURE_XSAVE,   X86_FEATURE_PKU },
+	{ X86_FEATURE_XSAVE,   X86_FEATURE_MPX },
+	{ X86_FEATURE_XSAVE,   X86_FEATURE_XGETBV1 },
+	{ X86_FEATURE_XMM,     X86_FEATURE_XMM2 },
+	{ X86_FEATURE_XMM2,    X86_FEATURE_XMM3 },
+	{ X86_FEATURE_XMM2,    X86_FEATURE_XMM4_1 },
+	{ X86_FEATURE_XMM2,    X86_FEATURE_XMM4_2 },
+	{ X86_FEATURE_XMM2,    X86_FEATURE_XMM3 },
+	{ X86_FEATURE_XMM2,    X86_FEATURE_PCLMULQDQ },
+	{ X86_FEATURE_XMM2,    X86_FEATURE_SSSE3 },
+	{ X86_FEATURE_FMA,     X86_FEATURE_AVX },
+	{ X86_FEATURE_XMM2,    X86_FEATURE_F16C },
+	{ X86_FEATURE_XMM2,    X86_FEATURE_AES },
+	{ X86_FEATURE_XSAVE,   X86_FEATURE_AVX },
+	{ X86_FEATURE_XSAVE,   X86_FEATURE_AVX512F },
+	{ X86_FEATURE_AVX512F, X86_FEATURE_AVX512IFMA },
+	{ X86_FEATURE_AVX512F, X86_FEATURE_AVX512PF },
+	{ X86_FEATURE_AVX512F, X86_FEATURE_AVX512ER },
+	{ X86_FEATURE_AVX512F, X86_FEATURE_AVX512CD },
+	{ X86_FEATURE_AVX512F, X86_FEATURE_AVX512DQ },
+	{ X86_FEATURE_AVX512F, X86_FEATURE_AVX512BW },
+	{ X86_FEATURE_AVX512F, X86_FEATURE_AVX512VL },
+	{ X86_FEATURE_AVX512F, X86_FEATURE_AVX512VBMI },
+	{ X86_FEATURE_AVX512F, X86_FEATURE_AVX512_4VNNIW },
+	{ X86_FEATURE_AVX512F, X86_FEATURE_AVX512_4FMAPS },
+	{ X86_FEATURE_AVX512F, X86_FEATURE_AVX512_VPOPCNTDQ },
+	{ X86_FEATURE_AVX,     X86_FEATURE_AVX2 },
+	{}
+};
+
+static void do_clear_cpu_cap(struct cpuinfo_x86 *cpu, int feat)
+{
+	int i, newfeat;
+	bool changed;
+
+	if (!cpu)
+		__setup_clear_cpu_cap(feat);
+	else
+		__clear_cpu_cap(cpu, feat);
+again:
+	changed = false;
+	for (i = 0; cpuid_deps[i].feature; i++) {
+		if (feat == cpuid_deps[i].feature) {
+			newfeat = cpuid_deps[i].dep;
+			if (!cpu)
+				__setup_clear_cpu_cap(newfeat);
+			else
+				__clear_cpu_cap(cpu, newfeat);
+			changed = true;
+		}
+	}
+	/* Handle multi-level dependencies */
+	if (changed) {
+		feat = newfeat;
+		goto again;
+	}
+}
+
+void clear_cpu_cap(struct cpuinfo_x86 *cpu, int feat)
+{
+	do_clear_cpu_cap(cpu, feat);
+}
+
+EXPORT_SYMBOL_GPL(clear_cpu_cap);
+
+void setup_clear_cpu_cap(int feat)
+{
+	do_clear_cpu_cap(NULL, feat);
+}
-- 
2.9.4

[PATCH v4 3/5] x86/cpuid: Make clearcpuid an early param

[Andi Kleen]

From: Andi Kleen <ak@linux.intel.com>

Make clearcpuid= an early param, to make sure it is parsed
before the XSAVE initialization. This allows to modify
XSAVE state by clearing specific CPUID bits.

Signed-off-by: Andi Kleen <ak@linux.intel.com>
---
 arch/x86/kernel/cpu/common.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 60b7aa6330ed..600e0cf714b9 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1285,7 +1285,7 @@ static __init int setup_disablecpuid(char *arg)
 
 	return 1;
 }
-__setup("clearcpuid=", setup_disablecpuid);
+early_param("clearcpuid", setup_disablecpuid);
 
 #ifdef CONFIG_X86_64
 struct desc_ptr idt_descr __ro_after_init = {
-- 
2.9.4

[PATCH v4 4/5] x86/xsave: Make XSAVE check the base CPUID features before enabling

[Andi Kleen]

From: Andi Kleen <ak@linux.intel.com>

Before enabling XSAVE, not only check the XSAVE specific CPUID bits,
but also the base CPUID features of the respective XSAVE feature.
This allows to disable individual XSAVE states using the existing
clearcpuid= option, which can be useful for performance testing
and debugging, and also in general avoids inconsistencies.

Signed-off-by: Andi Kleen <ak@linux.intel.com>
---
 arch/x86/kernel/fpu/xstate.c | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index c24ac1efb12d..8f0b96320cc9 100644
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -15,6 +15,7 @@
 #include <asm/fpu/xstate.h>
 
 #include <asm/tlbflush.h>
+#include <asm/cpufeature.h>
 
 /*
  * Although we spell it out in here, the Processor Trace
@@ -36,6 +37,19 @@ static const char *xfeature_names[] =
 	"unknown xstate feature"	,
 };
 
+static short xsave_cpuid_features[] = {
+	X86_FEATURE_FPU,
+	X86_FEATURE_XMM,
+	X86_FEATURE_AVX,
+	X86_FEATURE_MPX,
+	X86_FEATURE_MPX,
+	X86_FEATURE_AVX512F,
+	X86_FEATURE_AVX512F,
+	X86_FEATURE_AVX512F,
+	X86_FEATURE_INTEL_PT,
+	X86_FEATURE_PKU,
+};
+
 /*
  * Mask of xstate features supported by the CPU and the kernel:
  */
@@ -702,6 +716,7 @@ void __init fpu__init_system_xstate(void)
 	unsigned int eax, ebx, ecx, edx;
 	static int on_boot_cpu __initdata = 1;
 	int err;
+	int i;
 
 	WARN_ON_FPU(!on_boot_cpu);
 	on_boot_cpu = 0;
@@ -735,6 +750,13 @@ void __init fpu__init_system_xstate(void)
 		goto out_disable;
 	}
 
+	/*
+	 * Clear XSAVE features that are disabled in the normal CPUID.
+	 */
+	for (i = 0; i < ARRAY_SIZE(xsave_cpuid_features); i++)
+		if (!boot_cpu_has(xsave_cpuid_features[i]))
+			xfeatures_mask &= ~BIT(i);
+
 	xfeatures_mask &= fpu__get_supported_xfeatures_mask();
 
 	/* Enable xstate instructions to be able to continue with initialization: */
-- 
2.9.4

[PATCH v4 5/5] x86/xsave: Using generic CPUID clearing when disabling XSAVE

[Andi Kleen]

From: Andi Kleen <ak@linux.intel.com>

Now that the generic CPUID clearing understands dependencies,
it's enough to clear the XSAVE CPUID bit to clear all depending
features when XSAVE gets disabled.

So we don't need this hard to maintain explicit list
of features depending on XSAVE anymore. Just call the generic
clear_cpu_cap() function for XSAVE.

Signed-off-by: Andi Kleen <ak@linux.intel.com>
---
 arch/x86/kernel/fpu/xstate.c | 20 --------------------
 1 file changed, 20 deletions(-)

diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index 8f0b96320cc9..73c4fda76d32 100644
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -73,26 +73,6 @@ unsigned int fpu_user_xstate_size;
 void fpu__xstate_clear_all_cpu_caps(void)
 {
 	setup_clear_cpu_cap(X86_FEATURE_XSAVE);
-	setup_clear_cpu_cap(X86_FEATURE_XSAVEOPT);
-	setup_clear_cpu_cap(X86_FEATURE_XSAVEC);
-	setup_clear_cpu_cap(X86_FEATURE_XSAVES);
-	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_AVX512IFMA);
-	setup_clear_cpu_cap(X86_FEATURE_AVX512PF);
-	setup_clear_cpu_cap(X86_FEATURE_AVX512ER);
-	setup_clear_cpu_cap(X86_FEATURE_AVX512CD);
-	setup_clear_cpu_cap(X86_FEATURE_AVX512DQ);
-	setup_clear_cpu_cap(X86_FEATURE_AVX512BW);
-	setup_clear_cpu_cap(X86_FEATURE_AVX512VL);
-	setup_clear_cpu_cap(X86_FEATURE_MPX);
-	setup_clear_cpu_cap(X86_FEATURE_XGETBV1);
-	setup_clear_cpu_cap(X86_FEATURE_AVX512VBMI);
-	setup_clear_cpu_cap(X86_FEATURE_PKU);
-	setup_clear_cpu_cap(X86_FEATURE_AVX512_4VNNIW);
-	setup_clear_cpu_cap(X86_FEATURE_AVX512_4FMAPS);
-	setup_clear_cpu_cap(X86_FEATURE_AVX512_VPOPCNTDQ);
 }
 
 /*
-- 
2.9.4

Support generic disabling of all XSAVE features

[Andi Kleen]

For performance testing and debugging it can be useful to disable XSAVE
features individually. 

This patchkit hooks up XSAVE with the generic clearcpuid=... option,
so that disabling a CPUID feature automatically disables the respective
XSAVE feature.

It also cleans up CPUID dependency management. Currently it's
possible to generate configurations with cleacpuid that crash.

It replaces an earlier patchkit that did this with special
case options.

v1:
Initial post
v2:
Work around broken lguest by exporting set_cpu_cap
Repost with cover letter
v3:
Repost. No changes to code.
v4:
Rebase to latest tree. Repost.
v5:
Fix dependency algorithm. Clean dups in table. Rebase.
v6: 
Rebase. No changes to code.
v7:
Rebase. No changes to code.
v8:
Address all review comments. Add Reviewed-bys.
Dependency checker restructured for feature->dependency
Add missing dependency for AVX->AVX512F
v9:
Remove redundant dependency AVX512F->XSAVE
Add dependencies for SHA_NI->XMM, XMM->FXSR, FXSR_OPT->FXSR
v10:
Move clearcpuid= option parsing to early xsave parsing,
and don't move the FPU initialization.
Add new clear_bit32/set_bit32
Lots of smaller changes based on review feedback.

Support generic disabling of all XSAVE features

[Andi Kleen]

For performance testing and debugging it can be useful to disable XSAVE
features individually. 

This patchkit hooks up XSAVE with the generic clearcpuid=... option,
so that disabling a CPUID feature automatically disables the respective
XSAVE feature.

It also cleans up CPUID dependency management. Currently it's
possible to generate configurations with cleacpuid that crash.

It replaces an earlier patchkit that did this with special
case options.

v1:
Initial post
v2:
Work around broken lguest by exporting set_cpu_cap
Repost with cover letter
v3:
Repost. No changes to code.
v4:
Rebase to latest tree. Repost.
v5:
Fix dependency algorithm. Clean dups in table. Rebase.
v6: 
Rebase. No changes to code.
v7:
Rebase. No changes to code.
v8:
Address all review comments. Add Reviewed-bys.
Dependency checker restructured for feature->dependency
Add missing dependency for AVX->AVX512F
v9:
Remove redundant dependency AVX512F->XSAVE
Add dependencies for SHA_NI->XMM, XMM->FXSR, FXSR_OPT->FXSR

Support generic disabling of all XSAVE features

[Andi Kleen]

For performance testing and debugging it can be useful to disable XSAVE
features individually. 

This patchkit hooks up XSAVE with the generic clearcpuid=... option,
so that disabling a CPUID feature automatically disables the respective
XSAVE feature.

It also cleans up CPUID dependency management. Currently it's
possible to generate configurations with cleacpuid that crash.

It replaces an earlier patchkit that did this with special
case options.

v1:
Initial post
v2:
Work around broken lguest by exporting set_cpu_cap
Repost with cover letter
v3:
Repost. No changes to code.
v4:
Rebase to latest tree. Repost.
v5:
Fix dependency algorithm. Clean dups in table. Rebase.
v6: 
Rebase. No changes to code.
v7:
Rebase. No changes to code.
v8:
Address all review comments. Add Reviewed-bys.
Dependency checker restructured for feature->dependency
Add missing dependency for AVX->AVX512F

Support generic disabling of all XSAVE features

[Andi Kleen]

For performance testing and debugging it can be useful to disable XSAVE
features individually. 

This patchkit hooks up XSAVE with the generic clearcpuid=... option,
so that disabling a CPUID feature automatically disables the respective
XSAVE feature.

It also cleans up CPUID dependency management. Currently it's
possible to generate configurations with cleacpuid that crash.

It replaces an earlier patchkit that did this with special
case options.

v1:
Initial post
v2:
Work around broken lguest by exporting set_cpu_cap
Repost with cover letter
v3:
Repost. No changes to code.
v4:
Rebase to latest tree. Repost.
v5:
Fix dependency algorithm. Clean dups in table. Rebase.
v6: 
Rebase. No changes to code.
v7:
Rebase. No changes to code.

Support generic disabling of all XSAVE features

[Andi Kleen]

For performance testing and debugging it can be useful to disable XSAVE
features individually. This patchkit hooks up XSAVE with the
generic clearcpuid=... option, so that disabling a CPUID feature
automatically disables the respective XSAVE feature.

It also cleans up CPUID dependency management. Currently it's
possible to generate configurations with cleacpuid that crash.

It replaces an earlier patchkit that did this with special
case options.

v1:
Initial post
v2:
Work around broken lguest by exporting set_cpu_cap
Repost with cover letter
v3:
Repost. No changes to code.
v4:
Rebase to latest tree. Repost.
v5:
Fix dependency algorithm. Clean dups in table. Rebase.
v6: 
Rebase. No changes to code.

Support generic disabling of all XSAVE features

[Andi Kleen]

For performance testing and debugging it can be useful to disable XSAVE
features individually. This patchkit hooks up XSAVE with the
generic clearcpuid=... option, so that disabling a CPUID feature
automatically disables the respective XSAVE feature.

It also cleans up CPUID dependency management. Currently it's
possible to generate configurations with clearcpuid that crash.

It replaces an earlier patchkit that did this with special
case options.

v1:
Initial post
v2:
Work around broken lguest by exporting set_cpu_cap
Repost with cover letter
v3:
Repost. No changes to code.

Re: Support generic disabling of all XSAVE features

[Andi Kleen]

Andi Kleen <andi@firstfloor.org> writes:

Any comments on this patchkit? If there are no objections please merge.

-Andi

> For performance testing and debugging it can be useful to disable XSAVE
> features individually. This patchkit hooks up XSAVE with the
> generic clearcpuid=... option, so that disabling a CPUID feature
> automatically disables the respective XSAVE feature.
>
> It also cleans up CPUID dependency management. Currently it's
> possible to generate configurations with cleacpuid that crash.
>
> It replaces an earlier patchkit that did this with special
> case options.
>
> v1:
> Initial post
> v2:
> Work around broken lguest by exporting set_cpu_cap
> Repost with cover letter

Support generic disabling of all XSAVE features

[Andi Kleen]

For performance testing and debugging it can be useful to disable XSAVE
features individually. This patchkit hooks up XSAVE with the
generic clearcpuid=... option, so that disabling a CPUID feature
automatically disables the respective XSAVE feature.

It also cleans up CPUID dependency management. Currently it's
possible to generate configurations with cleacpuid that crash.

It replaces an earlier patchkit that did this with special
case options.

v1:
Initial post
v2:
Work around broken lguest by exporting set_cpu_cap
Repost with cover letter