[PATCH v5 14/15] KVM: s390: add and wire function gib_alert_irq_handler()

[Michael Mueller <mimu@xxxxxxxxxxxxx>]

The patch implements a handler for GIB alert interruptions
on the host. Its task is to alert guests that interrupts are
pending for them.

A GIB alert interrupt statistic counter is added as well:

$ cat /proc/interrupts
          CPU0       CPU1
  ...
  GAL:      23         37   [I/O] GIB Alert
  ...

Signed-off-by: Michael Mueller <mimu@xxxxxxxxxxxxx>
---
 arch/s390/include/asm/irq.h |  1 +
 arch/s390/include/asm/isc.h |  1 +
 arch/s390/kernel/irq.c      |  1 +
 arch/s390/kvm/interrupt.c   | 36 ++++++++++++++++++++++++++++++++++--
 4 files changed, 37 insertions(+), 2 deletions(-)

diff --git a/arch/s390/include/asm/irq.h b/arch/s390/include/asm/irq.h
index 2f7f27e5493f..afaf5e3c57fd 100644
--- a/arch/s390/include/asm/irq.h
+++ b/arch/s390/include/asm/irq.h
@@ -62,6 +62,7 @@ enum interruption_class {
 	IRQIO_MSI,
 	IRQIO_VIR,
 	IRQIO_VAI,
+	IRQIO_GAL,
 	NMI_NMI,
 	CPU_RST,
 	NR_ARCH_IRQS
diff --git a/arch/s390/include/asm/isc.h b/arch/s390/include/asm/isc.h
index 6cb9e2ed05b6..b2cc1ec78d06 100644
--- a/arch/s390/include/asm/isc.h
+++ b/arch/s390/include/asm/isc.h
@@ -21,6 +21,7 @@
 /* Adapter interrupts. */
 #define QDIO_AIRQ_ISC IO_SCH_ISC	/* I/O subchannel in qdio mode */
 #define PCI_ISC 2			/* PCI I/O subchannels */
+#define GAL_ISC 5			/* GIB alert */
 #define AP_ISC 6			/* adjunct processor (crypto) devices */
 
 /* Functions for registration of I/O interruption subclasses */
diff --git a/arch/s390/kernel/irq.c b/arch/s390/kernel/irq.c
index 0e8d68bac82c..0cd5a5f96729 100644
--- a/arch/s390/kernel/irq.c
+++ b/arch/s390/kernel/irq.c
@@ -88,6 +88,7 @@ static const struct irq_class irqclass_sub_desc[] = {
 	{.irq = IRQIO_MSI,  .name = "MSI", .desc = "[I/O] MSI Interrupt" },
 	{.irq = IRQIO_VIR,  .name = "VIR", .desc = "[I/O] Virtual I/O Devices"},
 	{.irq = IRQIO_VAI,  .name = "VAI", .desc = "[I/O] Virtual I/O Devices AI"},
+	{.irq = IRQIO_GAL,  .name = "GAL", .desc = "[I/O] GIB Alert"},
 	{.irq = NMI_NMI,    .name = "NMI", .desc = "[NMI] Machine Check"},
 	{.irq = CPU_RST,    .name = "RST", .desc = "[CPU] CPU Restart"},
 };
diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c
index 03e7ba4f215a..79b9c262479b 100644
--- a/arch/s390/kvm/interrupt.c
+++ b/arch/s390/kvm/interrupt.c
@@ -26,6 +26,7 @@
 #include <asm/gmap.h>
 #include <asm/switch_to.h>
 #include <asm/nmi.h>
+#include <asm/airq.h>
 #include "kvm-s390.h"
 #include "gaccess.h"
 #include "trace-s390.h"
@@ -3043,7 +3044,7 @@ static void __floating_airqs_kick(struct kvm *kvm)
 #define NONE_GISA_ADDR 0x00000001UL
 #define GISA_ADDR_MASK 0xfffff000UL
 
-static void __maybe_unused process_gib_alert_list(void)
+static void process_gib_alert_list(void)
 {
 	u32 final, next_alert, origin = 0UL;
 	struct kvm_s390_gisa *gisa;
@@ -3091,7 +3092,10 @@ void kvm_s390_gisa_clear(struct kvm *kvm)
 {
 	if (!kvm->arch.gisa)
 		return;
+	if (set_iam(kvm->arch.gisa, 0) == -EBUSY)
+		process_gib_alert_list();
 	nullify_gisa(kvm->arch.gisa);
+	set_iam(kvm->arch.gisa, kvm->arch.iam);
 	VM_EVENT(kvm, 3, "gisa 0x%pK cleared", kvm->arch.gisa);
 }
 
@@ -3111,6 +3115,8 @@ void kvm_s390_gisa_destroy(struct kvm *kvm)
 {
 	if (!kvm->arch.gisa)
 		return;
+	if (set_iam(kvm->arch.gisa, 0) == -EBUSY)
+		process_gib_alert_list();
 	kvm->arch.gisa = NULL;
 }
 
@@ -3159,11 +3165,23 @@ int kvm_s390_gisc_unregister(struct kvm *kvm, u32 gisc)
 }
 EXPORT_SYMBOL_GPL(kvm_s390_gisc_unregister);
 
+static void gib_alert_irq_handler(struct airq_struct *airq)
+{
+	inc_irq_stat(IRQIO_GAL);
+	process_gib_alert_list();
+}
+
+static struct airq_struct gib_alert_irq = {
+	.handler = gib_alert_irq_handler,
+	.lsi_ptr = &gib_alert_irq.lsi_mask,
+};
+
 void kvm_s390_gib_destroy(void)
 {
 	if (!gib)
 		return;
 	chsc_sgib(0);
+	unregister_adapter_interrupt(&gib_alert_irq);
 	free_page((unsigned long)gib);
 	gib = NULL;
 }
@@ -3183,16 +3201,30 @@ int kvm_s390_gib_init(u8 nisc)
 		goto out;
 	}
 
+	gib_alert_irq.isc = nisc;
+	if (register_adapter_interrupt(&gib_alert_irq)) {
+		pr_err("Registering the GIB alert interruption handler failed\n");
+		rc = -EIO;
+		goto out_free;
+	}
+
 	gib->nisc = nisc;
 	if (chsc_sgib((u32)(u64)gib)) {
 		pr_err("Associating the GIB with the AIV facility failed\n");
 		free_page((unsigned long)gib);
 		gib = NULL;
 		rc = -EIO;
-		goto out;
+		goto out_unreg;
 	}
 
 	KVM_EVENT(3, "gib 0x%pK (nisc=%d) initialized", gib, gib->nisc);
+	goto out;
+
+out_unreg:
+	unregister_adapter_interrupt(&gib_alert_irq);
+out_free:
+	free_page((unsigned long)gib);
+	gib = NULL;
 out:
 	return rc;
 }
-- 
2.13.4