Re: [PATCH v3 10/12] KVM: s390: add and wire function gib_alert_irq_handler()

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On 28/11/2018 11:19, Michael Mueller wrote:
The patch implements a handler for GIB alert interruptions
on the host. Its task is to alert storage backed guests that
interrupts are pending for them.

A GIB alert interrupt statistic counter is added as well:

$ cat /proc/interrupts
           CPU0       CPU1
   ...
   GAL:       0          0   [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   | 55 +++++++++++++++++++++++++++++++++++++--------
  arch/s390/kvm/kvm-s390.c    |  4 ++++
  arch/s390/kvm/kvm-s390.h    |  5 +++++
  6 files changed, 58 insertions(+), 9 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 dd80bdc056a5..dae78d91fa53 100644
--- a/arch/s390/kvm/interrupt.c
+++ b/arch/s390/kvm/interrupt.c
@@ -23,6 +23,7 @@
  #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"
@@ -2904,7 +2905,7 @@ static void nullify_gisa(struct kvm_s390_gisa *gisa)
  #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;
@@ -2953,6 +2954,9 @@ static void __maybe_unused process_gib_alert_list(void)
  void kvm_s390_gisa_clear(struct kvm *kvm)
  {
  	if (kvm->arch.gisa) {
+		kvm->arch.gisa->iam = 0;
+		while (in_alert_list(kvm->arch.gisa))
+			process_gib_alert_list();
  		nullify_gisa(kvm->arch.gisa);
  		VM_EVENT(kvm, 3, "gisa 0x%pK cleared", kvm->arch.gisa);
  	}
@@ -2964,9 +2968,9 @@ void kvm_s390_gisa_init(struct kvm *kvm)
  		kvm->arch.gisa = &kvm->arch.sie_page2->gisa;
  		kvm->arch.iam = 0;
  		spin_lock_init(&kvm->arch.iam_ref_lock);
-		VM_EVENT(kvm, 3, "gisa 0x%pK initialized", kvm->arch.gisa);
-		kvm_s390_gisa_clear(kvm);
+		nullify_gisa(kvm->arch.gisa);
  		kvm->arch.gib_in_use = !!gib;
+		VM_EVENT(kvm, 3, "gisa 0x%pK initialized", kvm->arch.gisa);
  	}
  }
@@ -2974,6 +2978,10 @@ void kvm_s390_gisa_destroy(struct kvm *kvm)
  {
  	if (!kvm->arch.gisa)
  		return;
+
+	kvm->arch.gisa->iam = 0;
+	while (in_alert_list(kvm->arch.gisa))
+		process_gib_alert_list();
  	kvm->arch.gisa = NULL;
  	kvm->arch.iam = 0;
  }
@@ -3019,36 +3027,65 @@ 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;
  }
int kvm_s390_gib_init(u8 nisc)
  {
+	int rc = 0;
+
  	if (!css_general_characteristics.aiv) {
  		KVM_EVENT(3, "%s", "gib not initialized, no AIV facility");
-		return 0;
+		goto out;
  	}
gib = (struct kvm_s390_gib *)get_zeroed_page(GFP_KERNEL | GFP_DMA);
  	if (!gib) {
  		KVM_EVENT(3, "gib 0x%pK memory allocation failed", gib);
-		return -ENOMEM;
+		rc = -ENOMEM;
+		goto out;
+	}
+
+	gib_alert_irq.isc = nisc;
+	if (register_adapter_interrupt(&gib_alert_irq)) {
+		KVM_EVENT(3, "gib 0x%pK GAI registration failed", gib);
+		rc = -EIO;
+		goto out_free;
  	}
gib->nisc = nisc;
  	if (chsc_sgib((u32)(u64)gib)) {
  		KVM_EVENT(3, "gib 0x%pK AIV association failed", gib);
-		free_page((unsigned long)gib);
-		gib = NULL;
-		return -EIO;
+		rc = -EIO;
+		goto out_unreg;
  	}
KVM_EVENT(3, "gib 0x%pK (nisc=%d) initialized", gib, gib->nisc);
-	return 0;
+	return rc;
+
+out_unreg:
+	unregister_adapter_interrupt(&gib_alert_irq);
+out_free:
+	free_page((unsigned long)gib);
+	gib = NULL;
+out:
+	return rc;
  }
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index e00eae7ec0b8..283c51362ca8 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -3531,6 +3531,10 @@ static int vcpu_post_run(struct kvm_vcpu *vcpu, int exit_reason)
  	vcpu->run->s.regs.gprs[15] = vcpu->arch.sie_block->gg15;
atomic_dec(&vcpu->kvm->arch.vcpus_in_sie);
+	if (vcpu->kvm->arch.gib_in_use &&
+	    !in_alert_list(vcpu->kvm->arch.gisa) &&
+	    !atomic_read(&vcpu->kvm->arch.vcpus_in_sie))
+		vcpu->kvm->arch.gisa->iam = vcpu->kvm->arch.iam;


Here, AFAIU, if the IAM is set, we must take care that not bit from IPM
for which IAM is set is also set otherwise we won't get an interruption.


--
Pierre Morel
Linux/KVM/QEMU in Böblingen - Germany




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