Patch "x86/fpu: Make XSAVE check the base CPUID features before enabling" 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/fpu: Make XSAVE check the base CPUID features before enabling

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-fpu-make-xsave-check-the-base-cpuid-features-before-enabling.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 14:56:44 -0700
Subject: x86/fpu: Make XSAVE check the base CPUID features before enabling

From: Andi Kleen <[email protected]>

commit ccb18db2ab9d923df07e7495123fe5fb02329713 upstream.

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.

---
 arch/x86/kernel/fpu/xstate.c |   23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

@@ -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[] __initdata = {
+	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:
  */

@@ -726,6 +740,7 @@ 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;

@@ -759,6 +774,14 @@ 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: */

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

queue-4.14/bitops-add-clear-set_bit32-to-linux-bitops.h.patch queue-4.14/x86-fpu-remove-the-explicit-clearing-of-xsave-dependent-features.patch 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-fpu-parse-clearcpuid-as-early-xsave-argument.patch queue-4.14/x86-fpu-make-xsave-check-the-base-cpuid-features-before-enabling.patch