svn commit: r334220 - stable/11/sys/dev/cpuctl

[Mark Johnston]

Author: markj
Date: Fri May 25 19:16:05 2018
New Revision: 334220
URL: https://svnweb.freebsd.org/changeset/base/334220

Log:
  MFC r334050, r334051:
  Flush caches before initiating a microcode update on Intel CPUs.
  
  Approved by:	re (gjb, kib)

Modified:
  stable/11/sys/dev/cpuctl/cpuctl.c
Directory Properties:
  stable/11/   (props changed)

Modified: stable/11/sys/dev/cpuctl/cpuctl.c
==============================================================================
--- stable/11/sys/dev/cpuctl/cpuctl.c	Fri May 25 19:12:30 2018	(r334219)
+++ stable/11/sys/dev/cpuctl/cpuctl.c	Fri May 25 19:16:05 2018	(r334220)
@@ -365,8 +365,10 @@ 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 seemingly
+	 * undocumented errata applying to some Broadwell CPUs.
 	 */
+	wbinvd();
 	wrmsr_safe(MSR_BIOS_UPDT_TRIG, (uintptr_t)(ptr));
 	wrmsr_safe(MSR_BIOS_SIGN, 0);