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From: John Baldwin <jhb@FreeBSD.org>
Date: Tue, 8 Apr 2014 21:02:04 +0000 (UTC)
To: src-committers@freebsd.org, svn-src-all@freebsd.org,
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Subject: svn commit: r264277 - head/usr.sbin/bhyve
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Author: jhb
Date: Tue Apr  8 21:02:03 2014
New Revision: 264277
URL: http://svnweb.freebsd.org/changeset/base/264277

Log:
  Handle single-byte reads from the bvmcons port (0x220) by returning
  0xff.  Some guests may attempt to read from this port to identify
  psuedo-PNP ISA devices.  (The ie(4) driver in FreeBSD/i386 is one
  example.)
  
  Reviewed by:	grehan

Modified:
  head/usr.sbin/bhyve/consport.c

Modified: head/usr.sbin/bhyve/consport.c
==============================================================================
--- head/usr.sbin/bhyve/consport.c	Tue Apr  8 20:59:02 2014	(r264276)
+++ head/usr.sbin/bhyve/consport.c	Tue Apr  8 21:02:03 2014	(r264277)
@@ -110,6 +110,15 @@ console_handler(struct vmctx *ctx, int v
 		return (0);
 	}
 
+	/*
+	 * Guests might probe this port to look for old ISA devices
+	 * using single-byte reads.  Return 0xff for those.
+	 */
+	if (bytes == 1 && in) {
+		*eax = 0xff;
+		return (0);
+	}
+
 	if (bytes != 4)
 		return (-1);