x86/cpufeature: Create a new synthetic cpu capability for machine check recovery

The Intel Software Developer Manual describes bit 24 in the MCG_CAP
MSR:

   MCG_SER_P (software error recovery support present) flag,
   bit 24 — Indicates (when set) that the processor supports
   software error recovery

But only some models with this capability bit set will actually
generate recoverable machine checks.

Check the model name and set a synthetic capability bit. Provide
a command line option to set this bit anyway in case the kernel
doesn't recognise the model name.

Signed-off-by: Tony Luck <tony.luck@intel.com>
Reviewed-by: Borislav Petkov <bp@suse.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/2e5bfb23c89800a036fb8a45fa97a74bb16bc362.1455732970.git.tony.luck@intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 13 insertions, 0 deletions

diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
index a006f4cd792b..b5b187c8cc07 100644
--- a/arch/x86/kernel/cpu/mcheck/mce.c
+++ b/arch/x86/kernel/cpu/mcheck/mce.c
@@ -1576,6 +1576,17 @@ static int __mcheck_cpu_apply_quirks(struct cpuinfo_x86 *c)
 
                 if (c->x86 == 6 && c->x86_model == 45)
                         quirk_no_way_out = quirk_sandybridge_ifu;
+                /*
+                 * MCG_CAP.MCG_SER_P is necessary but not sufficient to know
+                 * whether this processor will actually generate recoverable
+                 * machine checks. Check to see if this is an E7 model Xeon.
+                 * We can't do a model number check because E5 and E7 use the
+                 * same model number. E5 doesn't support recovery, E7 does.
+                 */
+                if (mca_cfg.recovery || (mca_cfg.ser &&
+                        !strncmp(c->x86_model_id,
+                                 "Intel(R) Xeon(R) CPU E7-", 24)))
+                        set_cpu_cap(c, X86_FEATURE_MCE_RECOVERY);
         }
         if (cfg->monarch_timeout < 0)
                 cfg->monarch_timeout = 0;
@@ -2028,6 +2039,8 @@ static int __init mcheck_enable(char *str)
                 cfg->bootlog = (str[0] == 'b');
         else if (!strcmp(str, "bios_cmci_threshold"))
                 cfg->bios_cmci_threshold = true;
+        else if (!strcmp(str, "recovery"))
+                cfg->recovery = true;
         else if (isdigit(str[0])) {
                 if (get_option(&str, &cfg->tolerant) == 2)
                         get_option(&str, &(cfg->monarch_timeout));