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From: Tycho Nightingale <tychon@FreeBSD.org>
Date: Tue, 15 Apr 2014 17:06:26 +0000 (UTC)
To: src-committers@freebsd.org, svn-src-all@freebsd.org,
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Subject: svn commit: r264509 - head/sys/amd64/vmm
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Author: tychon
Date: Tue Apr 15 17:06:26 2014
New Revision: 264509
URL: http://svnweb.freebsd.org/changeset/base/264509

Log:
  Local APIC access via 32-bit naturally-aligned loads is merely
  suggested in the SDM.  Since some OSes have implemented otherwise
  don't be too rigorous in enforcing it.
  
  Approved by:	grehan (co-mentor)

Modified:
  head/sys/amd64/vmm/vmm_lapic.c

Modified: head/sys/amd64/vmm/vmm_lapic.c
==============================================================================
--- head/sys/amd64/vmm/vmm_lapic.c	Tue Apr 15 16:31:23 2014	(r264508)
+++ head/sys/amd64/vmm/vmm_lapic.c	Tue Apr 15 17:06:26 2014	(r264509)
@@ -230,10 +230,12 @@ lapic_mmio_read(void *vm, int cpu, uint6
 	off = gpa - DEFAULT_APIC_BASE;
 
 	/*
-	 * Memory mapped local apic accesses must be 4 bytes wide and
-	 * aligned on a 16-byte boundary.
+	 * Memory mapped local apic accesses should be aligned on a
+	 * 16-byte boundary.  They are also suggested to be 4 bytes
+	 * wide, alas not all OSes follow suggestions.
 	 */
-	if (size != 4 || off & 0xf)
+	off &= ~3;
+	if (off & 0xf)
 		return (EINVAL);
 
 	vlapic = vm_lapic(vm, cpu);