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 bd9240a18
almost made me lose my lunch.

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Greg 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

diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c
index b720dac..5faa487 100644 (file)
--- a/arch/x86/kernel/cpu/intel.c
+++ b/arch/x86/kernel/cpu/intel.c
@@ -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:
         *