svn commit: r334050 - head/sys/dev/cpuctl

[Mark Johnston]

Author: markj
Date: Tue May 22 15:38:51 2018
New Revision: 334050
URL: https://svnweb.freebsd.org/changeset/base/334050

Log:
  Flush caches before initiating a microcode update on Intel CPUs.
  
  This apparently works around issues with updates of certain Broadwell
  CPUs.
  
  Reviewed by:	emaste, kib, sbruno
  MFC after:	3 days
  Differential Revision:	https://reviews.freebsd.org/D15520

Modified:
  head/sys/dev/cpuctl/cpuctl.c

Modified: head/sys/dev/cpuctl/cpuctl.c
==============================================================================
--- head/sys/dev/cpuctl/cpuctl.c	Tue May 22 15:35:38 2018	(r334049)
+++ head/sys/dev/cpuctl/cpuctl.c	Tue May 22 15:38:51 2018	(r334050)
@@ -367,8 +367,10 @@ update_intel(int cpu, cpuctl_update_args_t *args, stru
 	rdmsr_safe(MSR_BIOS_SIGN, &rev0); /* Get current microcode revision. */
 
 	/*
-	 * Perform update.
+	 * Perform update.  Flush caches first to work around seeingly
+	 * undocumented errata applying to some Broadwell CPUs.
 	 */
+	wbinvd();
 	wrmsr_safe(MSR_BIOS_UPDT_TRIG, (uintptr_t)(ptr));
 	wrmsr_safe(MSR_BIOS_SIGN, 0);