[PATCH v6 12/13] KVM: s390: add gib_alert_irq_handler()

Michael Mueller
2019-01-24T12:59:38Z

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@linux.ibm.com>
---
arch/s390/include/asm/irq.h | 1 +
arch/s390/include/asm/isc.h | 1 +
arch/s390/include/asm/kvm_host.h | 3 +
arch/s390/kernel/irq.c | 1 +
arch/s390/kvm/interrupt.c | 186 +++++++++++++++++++++++++++++++++++++--
arch/s390/kvm/kvm-s390.c | 2 +
6 files changed, 189 insertions(+), 5 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/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
index 2cfff617cb21..c5f51566ecd6 100644
--- a/arch/s390/include/asm/kvm_host.h
+++ b/arch/s390/include/asm/kvm_host.h
@@ -825,6 +825,9 @@ struct kvm_s390_gisa_iam {
struct kvm_s390_gisa_interrupt {
struct kvm_s390_gisa *origin;
struct kvm_s390_gisa_iam alert;
+ struct hrtimer timer;
+ u64 expires;
+ DECLARE_BITMAP(kicked_mask, KVM_MAX_VCPUS);
};

struct kvm_arch{
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 6bc9dab6d352..3294f77f4fce 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"
@@ -249,6 +250,57 @@ static inline int gisa_set_iam(struct kvm_s390_gisa *gisa, u8 iam)
return 0;
}

+/**
+ * gisa_clear_ipm - clear the GISA interruption pending mask
+ *
+ * @gisa: gisa to operate on
+ *
+ * Clear the IPM atomically with the next alert address and the IAM
+ * of the GISA unconditionally. All three fields are located in the
+ * first long word of the GISA.
+ */
+static inline void gisa_clear_ipm(struct kvm_s390_gisa *gisa)
+{
+ u64 word, _word;
+
+ do {
+ word = READ_ONCE(gisa->u64.word[0]);
+ _word = word & ~(0xffUL << 24);
+ } while (cmpxchg(&gisa->u64.word[0], word, _word) != word);
+}
+
+/**
+ * gisa_get_ipm_or_restore_iam - return IPM or restore GISA IAM
+ *
+ * @gi: gisa interrupt struct to work on
+ *
+ * Atomically restores the interruption alert mask if none of the
+ * relevant ISCs are pending and return the IPM.
+ *
+ * Returns: the relevant pending ISCs
+ */
+static inline u8 gisa_get_ipm_or_restore_iam(struct kvm_s390_gisa_interrupt *gi)
+{
+ u8 pending_mask, alert_mask;
+ u64 word, _word;
+
+ do {
+ word = READ_ONCE(gi->origin->u64.word[0]);
+ alert_mask = READ_ONCE(gi->alert.mask);
+ pending_mask = (u8)(word >> 24) & alert_mask;
+ if (pending_mask)
+ return pending_mask;
+ _word = (word & ~0xffUL) | alert_mask;
+ } while (cmpxchg(&gi->origin->u64.word[0], word, _word) != word);
+
+ return 0;
+}
+
+static inline int gisa_in_alert_list(struct kvm_s390_gisa *gisa)
+{
+ return READ_ONCE(gisa->next_alert) != (u32)(u64)gisa;
+}
+
static inline void gisa_set_ipm_gisc(struct kvm_s390_gisa *gisa, u32 gisc)
{
set_bit_inv(IPM_BIT_OFFSET + gisc, (unsigned long *) gisa);
@@ -2920,14 +2972,100 @@ int kvm_s390_get_irq_state(struct kvm_vcpu *vcpu, __u8 __user *buf, int len)
return n;
}

+static void __airqs_kick_single_vcpu(struct kvm *kvm, u8 deliverable_mask)
+{
+ int vcpu_id, online_vcpus = atomic_read(&kvm->online_vcpus);
+ struct kvm_s390_gisa_interrupt *gi = &kvm->arch.gisa_int;
+ struct kvm_vcpu *vcpu;
+
+ for_each_set_bit(vcpu_id, kvm->arch.idle_mask, online_vcpus) {
+ vcpu = kvm_get_vcpu(kvm, vcpu_id);
+ if (psw_ioint_disabled(vcpu))
+ continue;
+ deliverable_mask &= (u8)(vcpu->arch.sie_block->gcr[6] >> 24);
+ if (deliverable_mask) {
+ /* lately kicked but not yet running */
+ if (test_and_set_bit(vcpu_id, gi->kicked_mask))
+ return;
+ kvm_s390_vcpu_wakeup(vcpu);
+ return;
+ }
+ }
+}
+
+static enum hrtimer_restart gisa_vcpu_kicker(struct hrtimer *timer)
+{
+ struct kvm_s390_gisa_interrupt *gi =
+ container_of(timer, struct kvm_s390_gisa_interrupt, timer);
+ struct kvm *kvm =
+ container_of(gi->origin, struct sie_page2, gisa)->kvm;
+ u8 pending_mask;
+
+ pending_mask = gisa_get_ipm_or_restore_iam(gi);
+ if (pending_mask) {
+ __airqs_kick_single_vcpu(kvm, pending_mask);
+ hrtimer_forward_now(timer, ns_to_ktime(gi->expires));
+ return HRTIMER_RESTART;
+ };
+
+ return HRTIMER_NORESTART;
+}
+
+#define NULL_GISA_ADDR 0x00000000UL
+#define NONE_GISA_ADDR 0x00000001UL
+#define GISA_ADDR_MASK 0xfffff000UL
+
+static void process_gib_alert_list(void)
+{
+ struct kvm_s390_gisa_interrupt *gi;
+ struct kvm_s390_gisa *gisa;
+ struct kvm *kvm;
+ u32 final, origin = 0UL;
+
+ do {
+ /*
+ * If the NONE_GISA_ADDR is still stored in the alert list
+ * origin, we will leave the outer loop. No further GISA has
+ * been added to the alert list by millicode while processing
+ * the current alert list.
+ */
+ final = (origin & NONE_GISA_ADDR);
+ /*
+ * Cut off the alert list and store the NONE_GISA_ADDR in the
+ * alert list origin to avoid further GAL interruptions.
+ * A new alert list can be build up by millicode in parallel
+ * for guests not in the yet cut-off alert list. When in the
+ * final loop, store the NULL_GISA_ADDR instead. This will re-
+ * enable GAL interruptions on the host again.
+ */
+ origin = xchg(&gib->alert_list_origin,
+ (!final) ? NONE_GISA_ADDR : NULL_GISA_ADDR);
+ /*
+ * Loop through the just cut-off alert list and start the
+ * gisa timers to kick idle vcpus to consume the pending
+ * interruptions asap.
+ */
+ while (origin & GISA_ADDR_MASK) {
+ gisa = (struct kvm_s390_gisa *)(u64)origin;
+ origin = gisa->next_alert;
+ gisa->next_alert = (u32)(u64)gisa;
+ kvm = container_of(gisa, struct sie_page2, gisa)->kvm;
+ gi = &kvm->arch.gisa_int;
+ if (hrtimer_active(&gi->timer))
+ hrtimer_cancel(&gi->timer);
+ hrtimer_start(&gi->timer, 0, HRTIMER_MODE_REL);
+ }
+ } while (!final);
+
+}
+
void kvm_s390_gisa_clear(struct kvm *kvm)
{
struct kvm_s390_gisa_interrupt *gi = &kvm->arch.gisa_int;

if (!gi->origin)
return;
- memset(gi->origin, 0, sizeof(struct kvm_s390_gisa));
- gi->origin->next_alert = (u32)(u64)gi->origin;
+ gisa_clear_ipm(gi->origin);
VM_EVENT(kvm, 3, "gisa 0x%pK cleared", gi->origin);
}

@@ -2940,13 +3078,25 @@ void kvm_s390_gisa_init(struct kvm *kvm)
gi->origin = &kvm->arch.sie_page2->gisa;
gi->alert.mask = 0;
spin_lock_init(&gi->alert.ref_lock);
- kvm_s390_gisa_clear(kvm);
+ gi->expires = 50 * 1000; /* 50 usec */
+ hrtimer_init(&gi->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
+ gi->timer.function = gisa_vcpu_kicker;
+ memset(gi->origin, 0, sizeof(struct kvm_s390_gisa));
+ gi->origin->next_alert = (u32)(u64)gi->origin;
VM_EVENT(kvm, 3, "gisa 0x%pK initialized", gi->origin);
}

void kvm_s390_gisa_destroy(struct kvm *kvm)
{
- kvm->arch.gisa_int.origin = NULL;
+ struct kvm_s390_gisa_interrupt *gi = &kvm->arch.gisa_int;
+
+ if (!gi->origin)
+ return;
+ hrtimer_cancel(&gi->timer);
+ WRITE_ONCE(gi->alert.mask, 0);
+ while (gisa_in_alert_list(gi->origin))
+ cpu_relax();
+ gi->origin = NULL;
}

/**
@@ -3037,11 +3187,23 @@ 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;
}
@@ -3061,16 +3223,30 @@ 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;
+ }
+
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_gal;
}

KVM_EVENT(3, "gib 0x%pK (nisc=%d) initialized", gib, gib->nisc);
+ goto out;
+
+out_unreg_gal:
+ unregister_adapter_interrupt(&gib_alert_irq);
+out_free_gib:
+ 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 67023d5656fd..0e6ba4d17207 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -3460,6 +3460,8 @@ static int vcpu_pre_run(struct kvm_vcpu *vcpu)
kvm_s390_patch_guest_per_regs(vcpu);
}

+ clear_bit(vcpu->vcpu_id, vcpu->kvm->arch.gisa_int.kicked_mask);
+
vcpu->arch.sie_block->icptcode = 0;
cpuflags = atomic_read(&vcpu->arch.sie_block->cpuflags);
VCPU_EVENT(vcpu, 6, "entering sie flags %x", cpuflags);
--
2.13.4