Patch "x86/cpuid: Add generic table for CPUID dependencies" has been added to the 4.14-stable tree

This is a note to let you know that I've just added the patch titled

x86/cpuid: Add generic table for CPUID dependencies

to the 4.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
x86-cpuid-add-generic-table-for-cpuid-dependencies.patch
and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Andi Kleen <[email protected]>
Date: Fri, 13 Oct 2017 14:56:42 -0700
Subject: x86/cpuid: Add generic table for CPUID dependencies

From: Andi Kleen <[email protected]>

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.

---
 arch/x86/include/asm/cpufeature.h  |    9 +-
 arch/x86/include/asm/cpufeatures.h |    5 +
 arch/x86/kernel/cpu/Makefile       |    1 
 arch/x86/kernel/cpu/cpuid-deps.c   |  113 +++++++++++++++++++++++++++++++++++++
 4 files changed, 123 insertions(+), 5 deletions(-)

@@ -126,11 +126,10 @@ extern const char * const x86_bug_flags[
 #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);	\

@@ -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 */

@@ -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

Patches currently in stable-queue which might be from [email protected] are

queue-4.14/x86-cpuid-add-generic-table-for-cpuid-dependencies.patch queue-4.14/x86-cpuid-prevent-out-of-bound-access-in-do_clear_cpu_cap.patch queue-4.14/x86-cpuid-replace-set-clear_bit32.patch