[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>

3 files changed, 30 insertions, 3 deletions

diff --git a/arch/s390/include/asm/system.h b/arch/s390/include/asm/system.h
index 67ee6c3c6bb3..12be42baa055 100644
--- a/arch/s390/include/asm/system.h
+++ b/arch/s390/include/asm/system.h
@@ -110,6 +110,7 @@ extern void pfault_fini(void);
 #endif /* CONFIG_PFAULT */
 
 extern void cmma_init(void);
+extern int memcpy_real(void *, void *, size_t);
 
 #define finish_arch_switch(prev) do {					     \
 	set_fs(current->thread.mm_segment);				     \
diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c
index 29f65bce55e1..d7d24fc3d6b7 100644
--- a/arch/s390/kernel/smp.c
+++ b/arch/s390/kernel/smp.c
@@ -292,9 +292,9 @@ static void __init smp_get_save_area(unsigned int cpu, unsigned int phy_cpu)
 	zfcpdump_save_areas[cpu] = kmalloc(sizeof(struct save_area), GFP_KERNEL);
 	while (raw_sigp(phy_cpu, sigp_stop_and_store_status) == sigp_busy)
 		cpu_relax();
-	memcpy(zfcpdump_save_areas[cpu],
-	       (void *)(unsigned long) store_prefix() + SAVE_AREA_BASE,
-	       sizeof(struct save_area));
+	memcpy_real(zfcpdump_save_areas[cpu],
+		    (void *)(unsigned long) store_prefix() + SAVE_AREA_BASE,
+		    sizeof(struct save_area));
 }
 
 struct save_area *zfcpdump_save_areas[NR_CPUS + 1];
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;
+}