x86/cpuid: Add generic table for CPUID dependencies

commit 0b00de857a648dafe7020878c7a27cf776f5edf4 upstream.

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.

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Jonathan McDowell <noodles@earth.li>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20171013215645.23166-3-andi@firstfloor.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h
index 0dfa68438e80e70595deb0a20d237f8cb1b8d3f0..bf6a76202a779ee131b4df8c89449ab52abd0a79 100644 (file)
--- a/arch/x86/include/asm/cpufeature.h
+++ b/arch/x86/include/asm/cpufeature.h
@@ -126,11 +126,10 @@ 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 { \
-       clear_cpu_cap(&boot_cpu_data, bit);     \
-       set_bit(bit, (unsigned long *)cpu_caps_cleared); \
-} while (0)
+
+extern void setup_clear_cpu_cap(unsigned int bit);
+extern void clear_cpu_cap(struct cpuinfo_x86 *c, unsigned int bit);
+
 #define setup_force_cpu_cap(bit) do { \
        set_cpu_cap(&boot_cpu_data, bit);       \
        set_bit(bit, (unsigned long *)cpu_caps_set);    \

diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
index 793690fbda3625defd130262db1e94b57152c0bc..9a0a5b128a30acd90fc70dc9a36c61bab629f03d 100644 (file)
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -22,6 +22,11 @@
  * 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 c60922a6638573f2adc06739ed8c1540de38f4ca..90cb82dbba577cc3bd7dd1e9cf63ef9b89c89daa 100644 (file)
--- a/arch/x86/kernel/cpu/Makefile
+++ b/arch/x86/kernel/cpu/Makefile
@@ -23,6 +23,7 @@ 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 (file)
index 0000000..e48eb73
--- /dev/null
+++ b/arch/x86/kernel/cpu/cpuid-deps.c
@@ -0,0 +1,113 @@
+/* Declare dependencies between CPUIDs */
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <asm/cpufeature.h>
+
+struct cpuid_dep {
+       unsigned int    feature;
+       unsigned int    depends;
+};
+
+/*
+ * 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).
+ *
+ * Note this all is not __init / __initdata because it can be
+ * called from cpu hotplug. It shouldn't do anything in this case,
+ * but it's difficult to tell that to the init reference checker.
+ */
+const static struct cpuid_dep cpuid_deps[] = {
+       { 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_PKU,              X86_FEATURE_XSAVE     },
+       { X86_FEATURE_MPX,              X86_FEATURE_XSAVE     },
+       { X86_FEATURE_XGETBV1,          X86_FEATURE_XSAVE     },
+       { X86_FEATURE_FXSR_OPT,         X86_FEATURE_FXSR      },
+       { X86_FEATURE_XMM,              X86_FEATURE_FXSR      },
+       { X86_FEATURE_XMM2,             X86_FEATURE_XMM       },
+       { 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_XMM2,     },
+       { X86_FEATURE_F16C,             X86_FEATURE_XMM2,     },
+       { X86_FEATURE_AES,              X86_FEATURE_XMM2      },
+       { X86_FEATURE_SHA_NI,           X86_FEATURE_XMM2      },
+       { X86_FEATURE_FMA,              X86_FEATURE_AVX       },
+       { X86_FEATURE_AVX2,             X86_FEATURE_AVX,      },
+       { X86_FEATURE_AVX512F,          X86_FEATURE_AVX,      },
+       { 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_AVX512F   },
+       {}
+};
+
+static inline void __clear_cpu_cap(struct cpuinfo_x86 *c, unsigned int bit)
+{
+       clear_bit32(bit, c->x86_capability);
+}
+
+static inline void __setup_clear_cpu_cap(unsigned int bit)
+{
+       clear_cpu_cap(&boot_cpu_data, bit);
+       set_bit32(bit, cpu_caps_cleared);
+}
+
+static inline void clear_feature(struct cpuinfo_x86 *c, unsigned int feature)
+{
+       if (!c)
+               __setup_clear_cpu_cap(feature);
+       else
+               __clear_cpu_cap(c, feature);
+}
+
+static void do_clear_cpu_cap(struct cpuinfo_x86 *c, unsigned int feature)
+{
+       bool changed;
+       DECLARE_BITMAP(disable, NCAPINTS * sizeof(u32) * 8);
+       const struct cpuid_dep *d;
+
+       clear_feature(c, feature);
+
+       /* Collect all features to disable, handling dependencies */
+       memset(disable, 0, sizeof(disable));
+       __set_bit(feature, disable);
+
+       /* Loop until we get a stable state. */
+       do {
+               changed = false;
+               for (d = cpuid_deps; d->feature; d++) {
+                       if (!test_bit(d->depends, disable))
+                               continue;
+                       if (__test_and_set_bit(d->feature, disable))
+                               continue;
+
+                       changed = true;
+                       clear_feature(c, d->feature);
+               }
+       } while (changed);
+}
+
+void clear_cpu_cap(struct cpuinfo_x86 *c, unsigned int feature)
+{
+       do_clear_cpu_cap(c, feature);
+}
+
+void setup_clear_cpu_cap(unsigned int feature)
+{
+       do_clear_cpu_cap(NULL, feature);
+}