2 files changed, 40 insertions, 24 deletions

diff --git a/arch/s390/kernel/module.c b/arch/s390/kernel/module.c
index d52d85367bf7..b032e556eeb7 100644
--- a/arch/s390/kernel/module.c
+++ b/arch/s390/kernel/module.c
@@ -33,7 +33,7 @@
 #define DEBUGP(fmt , ...)
 #endif
 
-#define PLT_ENTRY_SIZE 20
+#define PLT_ENTRY_SIZE 22
 
 void *module_alloc(unsigned long size)
 {
@@ -341,27 +341,26 @@ static int apply_rela(Elf_Rela *rela, Elf_Addr base, Elf_Sym *symtab,
 	case R_390_PLTOFF32:	/* 32 bit offset from GOT to PLT. */
 	case R_390_PLTOFF64:	/* 16 bit offset from GOT to PLT. */
 		if (info->plt_initialized == 0) {
-			unsigned int insn[5];
-			unsigned int *ip = me->core_layout.base +
-					   me->arch.plt_offset +
-					   info->plt_offset;
-
-			insn[0] = 0x0d10e310;	/* basr 1,0  */
-			insn[1] = 0x100a0004;	/* lg	1,10(1) */
+			unsigned char insn[PLT_ENTRY_SIZE];
+			char *plt_base;
+			char *ip;
+
+			plt_base = me->core_layout.base + me->arch.plt_offset;
+			ip = plt_base + info->plt_offset;
+			*(int *)insn = 0x0d10e310;	/* basr 1,0  */
+			*(int *)&insn[4] = 0x100c0004;	/* lg	1,12(1) */
 			if (IS_ENABLED(CONFIG_EXPOLINE) && !nospec_disable) {
-				unsigned int *ij;
-				ij = me->core_layout.base +
-					me->arch.plt_offset +
-					me->arch.plt_size - PLT_ENTRY_SIZE;
-				insn[2] = 0xa7f40000 +	/* j __jump_r1 */
-					(unsigned int)(u16)
-					(((unsigned long) ij - 8 -
-					  (unsigned long) ip) / 2);
+				char *jump_r1;
+
+				jump_r1 = plt_base + me->arch.plt_size -
+					PLT_ENTRY_SIZE;
+				/* brcl	0xf,__jump_r1 */
+				*(short *)&insn[8] = 0xc0f4;
+				*(int *)&insn[10] = (jump_r1 - (ip + 8)) / 2;
 			} else {
-				insn[2] = 0x07f10000;	/* br %r1 */
+				*(int *)&insn[8] = 0x07f10000;	/* br %r1 */
 			}
-			insn[3] = (unsigned int) (val >> 32);
-			insn[4] = (unsigned int) val;
+			*(long *)&insn[14] = val;
 
 			write(ip, insn, sizeof(insn));
 			info->plt_initialized = 1;
diff --git a/arch/s390/kernel/nmi.c b/arch/s390/kernel/nmi.c
index 0c9e894913dc..651a51914e34 100644
--- a/arch/s390/kernel/nmi.c
+++ b/arch/s390/kernel/nmi.c
@@ -264,7 +264,14 @@ static int notrace s390_validate_registers(union mci mci, int umode)
 		/* Validate vector registers */
 		union ctlreg0 cr0;
 
-		if (!mci.vr) {
+		/*
+		 * The vector validity must only be checked if not running a
+		 * KVM guest. For KVM guests the machine check is forwarded by
+		 * KVM and it is the responsibility of the guest to take
+		 * appropriate actions. The host vector or FPU values have been
+		 * saved by KVM and will be restored by KVM.
+		 */
+		if (!mci.vr && !test_cpu_flag(CIF_MCCK_GUEST)) {
 			/*
 			 * Vector registers can't be restored. If the kernel
 			 * currently uses vector registers the system is
@@ -307,11 +314,21 @@ static int notrace s390_validate_registers(union mci mci, int umode)
 	if (cr2.gse) {
 		if (!mci.gs) {
 			/*
-			 * Guarded storage register can't be restored and
-			 * the current processes uses guarded storage.
-			 * It has to be terminated.
+			 * 2 cases:
+			 * - machine check in kernel or userspace
+			 * - machine check while running SIE (KVM guest)
+			 * For kernel or userspace the userspace values of
+			 * guarded storage control can not be recreated, the
+			 * process must be terminated.
+			 * For SIE the guest values of guarded storage can not
+			 * be recreated. This is either due to a bug or due to
+			 * GS being disabled in the guest. The guest will be
+			 * notified by KVM code and the guests machine check
+			 * handling must take care of this.  The host values
+			 * are saved by KVM and are not affected.
 			 */
-			kill_task = 1;
+			if (!test_cpu_flag(CIF_MCCK_GUEST))
+				kill_task = 1;
 		} else {
 			load_gs_cb((struct gs_cb *)mcesa->guarded_storage_save_area);
 		}