4.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: Jia Zhang qianyue.zj@alibaba-inc.com
commit b94b7373317164402ff7728d10f7023127a02b60 upstream.
Instead of blacklisting all model 79 CPUs when attempting a late microcode loading, limit that only to CPUs with microcode revisions < 0x0b000021 because only on those late loading may cause a system hang.
For such processors either:
a) a BIOS update which might contain a newer microcode revision
or
b) the early microcode loading method
should be considered.
Processors with revisions 0x0b000021 or higher will not experience such hangs.
For more details, see erratum BDF90 in document #334165 (Intel Xeon Processor E7-8800/4800 v4 Product Family Specification Update) from September 2017.
[ bp: Heavily massage commit message and pr_* statements. ]
Fixes: 723f2828a98c ("x86/microcode/intel: Disable late loading on model 79") Signed-off-by: Jia Zhang qianyue.zj@alibaba-inc.com Signed-off-by: Borislav Petkov bp@suse.de Signed-off-by: Thomas Gleixner tglx@linutronix.de Acked-by: Tony Luck tony.luck@intel.com Cc: x86-ml x86@kernel.org Link: http://lkml.kernel.org/r/1514772287-92959-1-git-send-email-qianyue.zj@alibab... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/x86/kernel/cpu/microcode/intel.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-)
--- a/arch/x86/kernel/cpu/microcode/intel.c +++ b/arch/x86/kernel/cpu/microcode/intel.c @@ -994,9 +994,17 @@ static bool is_blacklisted(unsigned int { struct cpuinfo_x86 *c = &cpu_data(cpu);
- if (c->x86 == 6 && c->x86_model == 79) { - pr_err_once("late loading on model 79 is disabled.\n"); - return true; + /* + * Late loading on model 79 with microcode revision less than 0x0b000021 + * may result in a system hang. This behavior is documented in item + * BDF90, #334165 (Intel Xeon Processor E7-8800/4800 v4 Product Family). + */ + if (c->x86 == 6 && + c->x86_model == 79 && + c->x86_mask == 0x01 && + c->microcode < 0x0b000021) { + pr_err_once("Erratum BDF90: late loading with revision < 0x0b000021 (0x%x) disabled.\n", c->microcode); + pr_err_once("Please consider either early loading through initrd/built-in or a potential BIOS update.\n"); }
return false;