[S390] zcore: CPU registers are not saved under LPAR

To save the registers for all CPUs a sigp "store status" is done that
stores the registers to address absolute zero. To access storage at
absolute zero, normally the address of the prefix register of the
accessing CPU has to be used. This does not work when large pages are
active (currently only under LPAR). In order to fix that problem,
instead of memcpy memcpy_real is used, which switches to real mode
where prefixing works.

Signed-off-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 26 insertions, 0 deletions

diff --git a/arch/s390/mm/maccess.c b/arch/s390/mm/maccess.c
index 81756271dc44..a8c2af8c650f 100644
--- a/arch/s390/mm/maccess.c
+++ b/arch/s390/mm/maccess.c
@@ -59,3 +59,29 @@ long probe_kernel_write(void *dst, void *src, size_t size)
 	}
 	return copied < 0 ? -EFAULT : 0;
 }
+
+int memcpy_real(void *dest, void *src, size_t count)
+{
+	register unsigned long _dest asm("2") = (unsigned long) dest;
+	register unsigned long _len1 asm("3") = (unsigned long) count;
+	register unsigned long _src  asm("4") = (unsigned long) src;
+	register unsigned long _len2 asm("5") = (unsigned long) count;
+	unsigned long flags;
+	int rc = -EFAULT;
+
+	if (!count)
+		return 0;
+	flags = __raw_local_irq_stnsm(0xf8UL);
+	asm volatile (
+		"0:	mvcle	%1,%2,0x0\n"
+		"1:	jo	0b\n"
+		"	lhi	%0,0x0\n"
+		"2:\n"
+		EX_TABLE(1b,2b)
+		: "+d" (rc), "+d" (_dest), "+d" (_src), "+d" (_len1),
+		  "+d" (_len2), "=m" (*((long *) dest))
+		: "m" (*((long *) src))
+		: "cc", "memory");
+	__raw_local_irq_ssm(flags);
+	return rc;
+}