svn commit: r272388 - stable/10/sys/amd64/vmm/io

[Peter Grehan]

Author: grehan
Date: Wed Oct  1 23:15:23 2014
New Revision: 272388
URL: https://svnweb.freebsd.org/changeset/base/272388

Log:
  MFC r272193
  
    Allow the PIC's IMR register to be read before ICW initialisation.
  
    As of git submit e179f6914152eca9, the Linux kernel does a simple
    probe of the PIC by writing a pattern to the IMR and then reading it
    back, prior to the init sequence of ICW words.
  
    The bhyve PIC emulation wasn't allowing the IMR to be read until
    the ICW sequence was complete. This limitation isn't required so
    relax the test.
  
    With this change, Linux kernels 3.15-rc2 and later won't hang
    on boot when calibrating the local APIC.
  
  Approved by: re (gjb)

Modified:
  stable/10/sys/amd64/vmm/io/vatpic.c
Directory Properties:
  stable/10/   (props changed)

Modified: stable/10/sys/amd64/vmm/io/vatpic.c
==============================================================================
--- stable/10/sys/amd64/vmm/io/vatpic.c	Wed Oct  1 22:18:07 2014	(r272387)
+++ stable/10/sys/amd64/vmm/io/vatpic.c	Wed Oct  1 23:15:23 2014	(r272388)
@@ -600,20 +600,19 @@ vatpic_write(struct vatpic *vatpic, stru
 	VATPIC_LOCK(vatpic);
 
 	if (port & ICU_IMR_OFFSET) {
-		if (atpic->ready) {
+		switch (atpic->icw_num) {
+		case 2:
+			error = vatpic_icw2(vatpic, atpic, val);
+			break;
+		case 3:
+			error = vatpic_icw3(vatpic, atpic, val);
+			break;
+		case 4:
+			error = vatpic_icw4(vatpic, atpic, val);
+			break;
+		default:
 			error = vatpic_ocw1(vatpic, atpic, val);
-		} else {
-			switch (atpic->icw_num) {
-			case 2:
-				error = vatpic_icw2(vatpic, atpic, val);
-				break;
-			case 3:
-				error = vatpic_icw3(vatpic, atpic, val);
-				break;
-			case 4:
-				error = vatpic_icw4(vatpic, atpic, val);
-				break;
-			}
+			break;
 		}
 	} else {
 		if (val & (1 << 4))