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From: Neel Natu <neel@FreeBSD.org>
Date: Tue, 26 Jan 2010 03:39:10 +0000 (UTC)
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Subject: svn commit: r203000 - head/sys/mips/sibyte
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Author: neel
Date: Tue Jan 26 03:39:10 2010
New Revision: 203000
URL: http://svn.freebsd.org/changeset/base/203000

Log:
  Install the XTLB exception handler for Sibyte processors.
  
  This is a workaround for the fact that the CFE is compiled as a 64-bit
  application and therefore sets the SR_KX bit every time we call into
  it (for e.g. console).
  
  A TLB miss for any address above 0xc0000000 with the SR_KX bit set will
  end up at the XTLB exception vector. We workaround this by copying the
  standard TLB handler at the XTLB exception vector.
  
  Approved by: imp (mentor)

Modified:
  head/sys/mips/sibyte/sb_machdep.c

Modified: head/sys/mips/sibyte/sb_machdep.c
==============================================================================
--- head/sys/mips/sibyte/sb_machdep.c	Tue Jan 26 03:29:52 2010	(r202999)
+++ head/sys/mips/sibyte/sb_machdep.c	Tue Jan 26 03:39:10 2010	(r203000)
@@ -93,6 +93,8 @@ extern void cfe_env_init(void);
 extern int *edata;
 extern int *end;
 
+extern char MipsTLBMiss[], MipsTLBMissEnd[];
+
 void
 platform_cpu_init()
 {
@@ -183,6 +185,28 @@ mips_init(void)
 	init_param1();
 	init_param2(physmem);
 	mips_cpu_init();
+
+	/*
+	 * XXX
+	 * The kernel is running in 32-bit mode but the CFE is running in
+	 * 64-bit mode. So the SR_KX bit in the status register is turned
+	 * on by the CFE every time we call into it - for e.g. CFE_CONSOLE.
+	 *
+	 * This means that if get a TLB miss for any address above 0xc0000000
+	 * and the SR_KX bit is set then we will end up in the XTLB exception
+	 * vector.
+	 *
+	 * For now work around this by copying the TLB exception handling
+	 * code to the XTLB exception vector.
+	 */
+	{
+		bcopy(MipsTLBMiss, (void *)XTLB_MISS_EXC_VEC,
+		      MipsTLBMissEnd - MipsTLBMiss);
+
+		mips_icache_sync_all();
+		mips_dcache_wbinv_all();
+	}
+
 	pmap_bootstrap();
 	mips_proc0_init();
 	mutex_init();