Merge branch 'parisc-3.12' of git://git.kernel.org/pub/scm/linux/kernel/git/deller/parisc-linux

torvalds · torvalds · commit a2ff82065b5b · 2013-10-27T10:45:00.000-07:00
Pull parisc fix from Helge Deller:
 "This is a 2-line patch to save the CPU register which holds our task
  thread info pointer before calling a firmware function and then to
  restore it again afterwards.

  This is necessary because on some 64bit machines the high-order 32bits
  are being clobbered by the firmware call, and thus we failed to bring
  up secondary CPUs (and instead crashed the kernel) in some situations
  eg if we had more than 4GB RAM.  This patch fixes a bug which has been
  since ever in the parisc linux kernel and which prevented some people
  to use a 64bit kernel"

* 'parisc-3.12' of git://git.kernel.org/pub/scm/linux/kernel/git/deller/parisc-linux:
  parisc: Do not crash 64bit SMP kernels on machines with &gt;= 4GB RAM
diff --git a/arch/parisc/kernel/head.S b/arch/parisc/kernel/head.S
@@ -195,6 +195,8 @@ common_stext:
 	ldw             MEM_PDC_HI(%r0),%r6
 	depd            %r6, 31, 32, %r3        /* move to upper word */
 
+	mfctl		%cr30,%r6		/* PCX-W2 firmware bug */
+
 	ldo             PDC_PSW(%r0),%arg0              /* 21 */
 	ldo             PDC_PSW_SET_DEFAULTS(%r0),%arg1 /* 2 */
 	ldo             PDC_PSW_WIDE_BIT(%r0),%arg2     /* 2 */
@@ -203,6 +205,8 @@ common_stext:
 	copy            %r0,%arg3
 
 stext_pdc_ret:
+	mtctl		%r6,%cr30		/* restore task thread info */
+
 	/* restore rfi target address*/
 	ldd             TI_TASK-THREAD_SZ_ALGN(%sp), %r10
 	tophys_r1       %r10
