[PATCH 01/12] x86, pkeys: cpuid bit definition

[Dave Hansen]

There are two CPUID bits for protection keys.  One is for whether
the CPU contains the feature, and the other will appear set once
the OS enables protection keys.  Specifically:

	Bit 04: OSPKE. If 1, OS has set CR4.PKE to enable
	Protection keys (and the RDPKRU/WRPKRU instructions)

This is because userspace can not see CR4 contents, but it can
see CPUID contents.

X86_FEATURE_PKU is referred to as "PKU" in the hardware documentation:

	CPUID.(EAX=07H,ECX=0H):ECX.PKU [bit 3]

X86_FEATURE_OSPKE is "OSPKU":

	CPUID.(EAX=07H,ECX=0H):ECX.OSPKE [bit 4]

These are the first CPU features which need to look at the
ECX word in CPUID leaf 0x7, so this patch also includes
fetching that word in to the cpuinfo->x86_capability[] array.

---

 b/arch/x86/include/asm/cpufeature.h |    6 +++++-
 b/arch/x86/kernel/cpu/common.c      |    1 +
 2 files changed, 6 insertions(+), 1 deletion(-)

diff -puN arch/x86/include/asm/cpufeature.h~pkeys-0-cpuid arch/x86/include/asm/cpufeature.h
--- a/arch/x86/include/asm/cpufeature.h~pkeys-0-cpuid	2015-05-07 10:31:40.985169281 -0700
+++ b/arch/x86/include/asm/cpufeature.h	2015-05-07 10:31:40.991169552 -0700
@@ -12,7 +12,7 @@
 #include <asm/disabled-features.h>
 #endif
 
-#define NCAPINTS	13	/* N 32-bit words worth of info */
+#define NCAPINTS	14	/* N 32-bit words worth of info */
 #define NBUGINTS	1	/* N 32-bit bug flags */
 
 /*
@@ -252,6 +252,10 @@
 /* Intel-defined CPU QoS Sub-leaf, CPUID level 0x0000000F:1 (edx), word 12 */
 #define X86_FEATURE_CQM_OCCUP_LLC (12*32+ 0) /* LLC occupancy monitoring if 1 */
 
+/* Intel-defined CPU features, CPUID level 0x00000007:0 (ecx), word 13 */
+#define X86_FEATURE_PKU		(13*32+ 3) /* Protection Keys for Userspace */
+#define X86_FEATURE_OSPKE	(13*32+ 4) /* OS Protection Keys Enable */
+
 /*
  * BUG word(s)
  */
diff -puN arch/x86/kernel/cpu/common.c~pkeys-0-cpuid arch/x86/kernel/cpu/common.c
--- a/arch/x86/kernel/cpu/common.c~pkeys-0-cpuid	2015-05-07 10:31:40.987169371 -0700
+++ b/arch/x86/kernel/cpu/common.c	2015-05-07 10:31:40.991169552 -0700
@@ -635,6 +635,7 @@ void get_cpu_cap(struct cpuinfo_x86 *c)
 		cpuid_count(0x00000007, 0, &eax, &ebx, &ecx, &edx);
 
 		c->x86_capability[9] = ebx;
+		c->x86_capability[13] = ecx;
 	}
 
 	/* Extended state features: level 0x0000000d */
_
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/