s390/nmi: move storage error checking back to C, enter with DAT on

Checking for storage errors in machine check entry code was done in order
to handle also storage errors on kernel page tables. However this is
extremely unlikely and some basic assumptions what works on machine check
entry are necessary anyway. In order to simplify machine check handling
delay checking for storage errors to C code.
With this also change the machine check new PSW to have DAT on, which
simplifies the entry code even further.
Reviewed-by: Alexander Gordeev <agordeev@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>

arch/s390/kernel/entry.S

@@ -122,24 +122,6 @@ _LPP_OFFSET	= __LC_LPP
 		    "jnz .+8; .insn rrf,0xb2e80000,0,0,13,0", 82
 	.endm
 
-	/*
-	 * The CHKSTG macro jumps to the provided label in case the
-	 * machine check interruption code reports one of unrecoverable
-	 * storage errors:
-	 * - Storage error uncorrected
-	 * - Storage key error uncorrected
-	 * - Storage degradation with Failing-storage-address validity
-	 */
-	.macro CHKSTG errlabel
-	TSTMSK	__LC_MCCK_CODE,(MCCK_CODE_STG_ERROR|MCCK_CODE_STG_KEY_ERROR)
-	jnz	\errlabel
-	TSTMSK	__LC_MCCK_CODE,MCCK_CODE_STG_DEGRAD
-	jz	.Loklabel\@
-	TSTMSK	__LC_MCCK_CODE,MCCK_CODE_STG_FAIL_ADDR
-	jnz	\errlabel
-.Loklabel\@:
-	.endm
-
 #if IS_ENABLED(CONFIG_KVM)
 	/*
 	 * The OUTSIDE macro jumps to the provided label in case the value
@@ -546,26 +528,18 @@ ENTRY(mcck_int_handler)
 3:	TSTMSK	__LC_MCCK_CODE,MCCK_CODE_PSW_MWP_VALID
 	jno	.Lmcck_panic
 	tmhh	%r8,0x0001		# interrupting from user ?
-	jnz	6f
+	jnz	.Lmcck_user
 	TSTMSK	__LC_MCCK_CODE,MCCK_CODE_PSW_IA_VALID
 	jno	.Lmcck_panic
 #if IS_ENABLED(CONFIG_KVM)
-	OUTSIDE	%r9,.Lsie_gmap,.Lsie_done,6f
+	OUTSIDE	%r9,.Lsie_gmap,.Lsie_done,.Lmcck_stack
 	OUTSIDE	%r9,.Lsie_entry,.Lsie_leave,4f
 	oi	__LC_CPU_FLAGS+7, _CIF_MCCK_GUEST
-	j	5f
-4:	CHKSTG	.Lmcck_panic
-5:	larl	%r14,.Lstosm_tmp
-	stosm	0(%r14),0x04		# turn dat on, keep irqs off
-	BPENTER	__SF_SIE_FLAGS(%r15),(_TIF_ISOLATE_BP|_TIF_ISOLATE_BP_GUEST)
+4:	BPENTER	__SF_SIE_FLAGS(%r15),(_TIF_ISOLATE_BP|_TIF_ISOLATE_BP_GUEST)
 	SIEEXIT
 	j	.Lmcck_stack
 #endif
-6:	CHKSTG	.Lmcck_panic
-	larl	%r14,.Lstosm_tmp
-	stosm	0(%r14),0x04		# turn dat on, keep irqs off
-	tmhh	%r8,0x0001		# interrupting from user ?
-	jz	.Lmcck_stack
+.Lmcck_user:
 	BPENTER __TI_flags(%r12),_TIF_ISOLATE_BP
 .Lmcck_stack:
 	lg	%r15,__LC_MCCK_STACK

arch/s390/kernel/nmi.c

@@ -487,7 +487,21 @@ int notrace s390_do_machine_check(struct pt_regs *regs)
 			mcck->stp_queue |= stp_island_check();
 		mcck_pending = 1;
 	}
-
+	/*
+	 * Reinject storage related machine checks into the guest if they
+	 * happen when the guest is running.
+	 */
+	if (!test_cpu_flag(CIF_MCCK_GUEST)) {
+		/* Storage error uncorrected */
+		if (mci.se)
+			s390_handle_damage();
+		/* Storage key-error uncorrected */
+		if (mci.ke)
+			s390_handle_damage();
+		/* Storage degradation */
+		if (mci.ds && mci.fa)
+			s390_handle_damage();
+	}
 	if (mci.cp) {
 		/* Channel report word pending */
 		mcck->channel_report = 1;

arch/s390/kernel/setup.c

@@ -437,7 +437,7 @@ static void __init setup_lowcore_dat_off(void)
 	lc->svc_new_psw.addr = (unsigned long) system_call;
 	lc->program_new_psw.mask = int_psw_mask | PSW_MASK_MCHECK;
 	lc->program_new_psw.addr = (unsigned long) pgm_check_handler;
-	lc->mcck_new_psw.mask = PSW_KERNEL_BITS;
+	lc->mcck_new_psw.mask = int_psw_mask;
 	lc->mcck_new_psw.addr = (unsigned long) mcck_int_handler;
 	lc->io_new_psw.mask = int_psw_mask | PSW_MASK_MCHECK;
 	lc->io_new_psw.addr = (unsigned long) io_int_handler;
@@ -512,6 +512,7 @@ static void __init setup_lowcore_dat_on(void)
 	S390_lowcore.external_new_psw.mask |= PSW_MASK_DAT;
 	S390_lowcore.svc_new_psw.mask |= PSW_MASK_DAT;
 	S390_lowcore.program_new_psw.mask |= PSW_MASK_DAT;
+	S390_lowcore.mcck_new_psw.mask |= PSW_MASK_DAT;
 	S390_lowcore.io_new_psw.mask |= PSW_MASK_DAT;
 	__ctl_set_bit(0, 28);
 	__ctl_store(S390_lowcore.cregs_save_area, 0, 15);