Commit a5b29663 authored by David Woodhouse's avatar David Woodhouse Committed by Thomas Gleixner
Browse files

x86/cpufeature: Blacklist SPEC_CTRL/PRED_CMD on early Spectre v2 microcodes 



This doesn't refuse to load the affected microcodes; it just refuses to
use the Spectre v2 mitigation features if they're detected, by clearing
the appropriate feature bits.

The AMD CPUID bits are handled here too, because hypervisors *may* have
been exposing those bits even on Intel chips, for fine-grained control
of what's available.

It is non-trivial to use x86_match_cpu() for this table because that
doesn't handle steppings. And the approach taken in commit bd9240a1
almost made me lose my lunch.

Signed-off-by: default avatarDavid Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Reviewed-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: gnomes@lxorguk.ukuu.org.uk
Cc: ak@linux.intel.com
Cc: ashok.raj@intel.com
Cc: dave.hansen@intel.com
Cc: karahmed@amazon.de
Cc: arjan@linux.intel.com
Cc: torvalds@linux-foundation.org
Cc: peterz@infradead.org
Cc: bp@alien8.de
Cc: pbonzini@redhat.com
Cc: tim.c.chen@linux.intel.com
Cc: gregkh@linux-foundation.org
Link: https://lkml.kernel.org/r/1516896855-7642-7-git-send-email-dwmw@amazon.co.uk
parent fec9434a

arch/x86/kernel/cpu/intel.c

+66 −0
Original line number Diff line number Diff line
@@ -102,6 +102,59 @@ static void probe_xeon_phi_r3mwait(struct cpuinfo_x86 *c) 
		ELF_HWCAP2 |= HWCAP2_RING3MWAIT;

}



/*

 * Early microcode releases for the Spectre v2 mitigation were broken.

 * Information taken from;

 * - https://newsroom.intel.com/wp-content/uploads/sites/11/2018/01/microcode-update-guidance.pdf

 * - https://kb.vmware.com/s/article/52345

 * - Microcode revisions observed in the wild

 * - Release note from 20180108 microcode release

 */

struct sku_microcode {

	u8 model;

	u8 stepping;

	u32 microcode;

};

static const struct sku_microcode spectre_bad_microcodes[] = {

	{ INTEL_FAM6_KABYLAKE_DESKTOP,	0x0B,	0x84 },

	{ INTEL_FAM6_KABYLAKE_DESKTOP,	0x0A,	0x84 },

	{ INTEL_FAM6_KABYLAKE_DESKTOP,	0x09,	0x84 },

	{ INTEL_FAM6_KABYLAKE_MOBILE,	0x0A,	0x84 },

	{ INTEL_FAM6_KABYLAKE_MOBILE,	0x09,	0x84 },

	{ INTEL_FAM6_SKYLAKE_X,		0x03,	0x0100013e },

	{ INTEL_FAM6_SKYLAKE_X,		0x04,	0x0200003c },

	{ INTEL_FAM6_SKYLAKE_MOBILE,	0x03,	0xc2 },

	{ INTEL_FAM6_SKYLAKE_DESKTOP,	0x03,	0xc2 },

	{ INTEL_FAM6_BROADWELL_CORE,	0x04,	0x28 },

	{ INTEL_FAM6_BROADWELL_GT3E,	0x01,	0x1b },

	{ INTEL_FAM6_BROADWELL_XEON_D,	0x02,	0x14 },

	{ INTEL_FAM6_BROADWELL_XEON_D,	0x03,	0x07000011 },

	{ INTEL_FAM6_BROADWELL_X,	0x01,	0x0b000025 },

	{ INTEL_FAM6_HASWELL_ULT,	0x01,	0x21 },

	{ INTEL_FAM6_HASWELL_GT3E,	0x01,	0x18 },

	{ INTEL_FAM6_HASWELL_CORE,	0x03,	0x23 },

	{ INTEL_FAM6_HASWELL_X,		0x02,	0x3b },

	{ INTEL_FAM6_HASWELL_X,		0x04,	0x10 },

	{ INTEL_FAM6_IVYBRIDGE_X,	0x04,	0x42a },

	/* Updated in the 20180108 release; blacklist until we know otherwise */

	{ INTEL_FAM6_ATOM_GEMINI_LAKE,	0x01,	0x22 },

	/* Observed in the wild */

	{ INTEL_FAM6_SANDYBRIDGE_X,	0x06,	0x61b },

	{ INTEL_FAM6_SANDYBRIDGE_X,	0x07,	0x712 },

};



static bool bad_spectre_microcode(struct cpuinfo_x86 *c)

{

	int i;



	for (i = 0; i < ARRAY_SIZE(spectre_bad_microcodes); i++) {

		if (c->x86_model == spectre_bad_microcodes[i].model &&

		    c->x86_mask == spectre_bad_microcodes[i].stepping)

			return (c->microcode <= spectre_bad_microcodes[i].microcode);

	}

	return false;

}



static void early_init_intel(struct cpuinfo_x86 *c)

{

	u64 misc_enable;
@@ -122,6 +175,19 @@ static void early_init_intel(struct cpuinfo_x86 *c) 
	if (c->x86 >= 6 && !cpu_has(c, X86_FEATURE_IA64))

		c->microcode = intel_get_microcode_revision();



	if ((cpu_has(c, X86_FEATURE_SPEC_CTRL) ||

	     cpu_has(c, X86_FEATURE_STIBP) ||

	     cpu_has(c, X86_FEATURE_AMD_SPEC_CTRL) ||

	     cpu_has(c, X86_FEATURE_AMD_PRED_CMD) ||

	     cpu_has(c, X86_FEATURE_AMD_STIBP)) && bad_spectre_microcode(c)) {

		pr_warn("Intel Spectre v2 broken microcode detected; disabling SPEC_CTRL\n");

		clear_cpu_cap(c, X86_FEATURE_SPEC_CTRL);

		clear_cpu_cap(c, X86_FEATURE_STIBP);

		clear_cpu_cap(c, X86_FEATURE_AMD_SPEC_CTRL);

		clear_cpu_cap(c, X86_FEATURE_AMD_PRED_CMD);

		clear_cpu_cap(c, X86_FEATURE_AMD_STIBP);

	}



	/*

	 * Atom erratum AAE44/AAF40/AAG38/AAH41:

	 *

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