s390/wti: Introduce infrastructure for warning track interrupt

The warning-track interrupt (wti) provides a notification that the
receiving CPU will be pre-empted from its physical CPU within a short
time frame. This time frame is called grace period and depends on the
machine type. Giving up the CPU on time may prevent a task to get stuck
while holding a resource.

Reviewed-by: Heiko Carstens <[email protected]>
Reviewed-by: Mete Durlu <[email protected]>
Signed-off-by: Tobias Huschle <[email protected]>
Signed-off-by: Vasily Gorbik <[email protected]>

Author: tobias-huschle

arch/s390/include/asm/ctlreg.h

@@ -202,8 +202,9 @@ union ctlreg0 {
 		unsigned long	   : 3;
 		unsigned long ccc  : 1; /* Cryptography counter control */
 		unsigned long pec  : 1; /* PAI extension control */
-		unsigned long	   : 17;
-		unsigned long	   : 3;
+		unsigned long	   : 15;
+		unsigned long wti  : 1; /* Warning-track */
+		unsigned long	   : 4;
 		unsigned long lap  : 1; /* Low-address-protection control */
 		unsigned long	   : 4;
 		unsigned long edat : 1; /* Enhanced-DAT-enablement control */

arch/s390/include/asm/diag.h

@@ -38,6 +38,7 @@ enum diag_stat_enum {
 	DIAG_STAT_X308,
 	DIAG_STAT_X318,
 	DIAG_STAT_X320,
+	DIAG_STAT_X49C,
 	DIAG_STAT_X500,
 	NR_DIAG_STAT
 };
@@ -363,4 +364,12 @@ void _diag0c_amode31(unsigned long rx);
 void _diag308_reset_amode31(void);
 int _diag8c_amode31(struct diag8c *addr, struct ccw_dev_id *devno, size_t len);
 
+/* diag 49c subcodes */
+enum diag49c_sc {
+	DIAG49C_SUBC_ACK = 0,
+	DIAG49C_SUBC_REG = 1
+};
+
+int diag49c(unsigned long subcode);
+
 #endif /* _ASM_S390_DIAG_H */

arch/s390/include/asm/irq.h

@@ -47,6 +47,7 @@ enum interruption_class {
 	IRQEXT_CMS,
 	IRQEXT_CMC,
 	IRQEXT_FTP,
+	IRQEXT_WTI,
 	IRQIO_CIO,
 	IRQIO_DAS,
 	IRQIO_C15,
@@ -99,6 +100,7 @@ int unregister_external_irq(u16 code, ext_int_handler_t handler);
 enum irq_subclass {
 	IRQ_SUBCLASS_MEASUREMENT_ALERT = 5,
 	IRQ_SUBCLASS_SERVICE_SIGNAL = 9,
+	IRQ_SUBCLASS_WARNING_TRACK = 33,
 };
 
 #define CR0_IRQ_SUBCLASS_MASK					  \

arch/s390/include/asm/sclp.h

@@ -72,6 +72,7 @@ struct sclp_info {
 	unsigned char has_core_type : 1;
 	unsigned char has_sprp : 1;
 	unsigned char has_hvs : 1;
+	unsigned char has_wti : 1;
 	unsigned char has_esca : 1;
 	unsigned char has_sief2 : 1;
 	unsigned char has_64bscao : 1;

arch/s390/kernel/diag.c

@@ -52,6 +52,7 @@ static const struct diag_desc diag_map[NR_DIAG_STAT] = {
 	[DIAG_STAT_X308] = { .code = 0x308, .name = "List-Directed IPL" },
 	[DIAG_STAT_X318] = { .code = 0x318, .name = "CP Name and Version Codes" },
 	[DIAG_STAT_X320] = { .code = 0x320, .name = "Certificate Store" },
+	[DIAG_STAT_X49C] = { .code = 0x49c, .name = "Warning-Track Interruption" },
 	[DIAG_STAT_X500] = { .code = 0x500, .name = "Virtio Service" },
 };
 
@@ -303,3 +304,19 @@ int diag26c(void *req, void *resp, enum diag26c_sc subcode)
 	return diag_amode31_ops.diag26c(virt_to_phys(req), virt_to_phys(resp), subcode);
 }
 EXPORT_SYMBOL(diag26c);
+
+int diag49c(unsigned long subcode)
+{
+	int rc;
+
+	diag_stat_inc(DIAG_STAT_X49C);
+	asm volatile(
+		"	diag	%[subcode],0,0x49c\n"
+		"	ipm	%[rc]\n"
+		"	srl	%[rc],28\n"
+		: [rc] "=d" (rc)
+		: [subcode] "d" (subcode)
+		: "cc");
+	return rc;
+}
+EXPORT_SYMBOL(diag49c);

arch/s390/kernel/irq.c

@@ -76,6 +76,7 @@ static const struct irq_class irqclass_sub_desc[] = {
 	{.irq = IRQEXT_CMS, .name = "CMS", .desc = "[EXT] CPU-Measurement: Sampling"},
 	{.irq = IRQEXT_CMC, .name = "CMC", .desc = "[EXT] CPU-Measurement: Counter"},
 	{.irq = IRQEXT_FTP, .name = "FTP", .desc = "[EXT] HMC FTP Service"},
+	{.irq = IRQEXT_WTI, .name = "WTI", .desc = "[EXT] Warning Track"},
 	{.irq = IRQIO_CIO,  .name = "CIO", .desc = "[I/O] Common I/O Layer Interrupt"},
 	{.irq = IRQIO_DAS,  .name = "DAS", .desc = "[I/O] DASD"},
 	{.irq = IRQIO_C15,  .name = "C15", .desc = "[I/O] 3215"},

drivers/s390/char/sclp_early.c

@@ -44,6 +44,7 @@ static void __init sclp_early_facilities_detect(void)
 	sclp.has_ibs = !!(sccb->fac117 & 0x20);
 	sclp.has_gisaf = !!(sccb->fac118 & 0x08);
 	sclp.has_hvs = !!(sccb->fac119 & 0x80);
+	sclp.has_wti = !!(sccb->fac119 & 0x40);
 	sclp.has_kss = !!(sccb->fac98 & 0x01);
 	sclp.has_aisii = !!(sccb->fac118 & 0x40);
 	sclp.has_aeni = !!(sccb->fac118 & 0x20);