Re: [PATCH v2 16/30] KVM: s390: pci: enable host forwarding of Adapter Event Notifications

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On 1/17/22 12:38 PM, Pierre Morel wrote:

...
+static void aen_process_gait(u8 isc)
+{
+    bool found = false, first = true;
+    union zpci_sic_iib iib = {{0}};
+    unsigned long si, flags;
+
+    spin_lock_irqsave(&aift->gait_lock, flags);
+
+    if (!aift->gait) {
+        spin_unlock_irqrestore(&aift->gait_lock, flags);
+        return;
+    }
+
+    for (si = 0;;) {
+        /* Scan adapter summary indicator bit vector */
+        si = airq_iv_scan(aift->sbv, si, airq_iv_end(aift->sbv));
+        if (si == -1UL) {
+            if (first || found) {
+                /* Reenable interrupts. */
+                if (zpci_set_irq_ctrl(SIC_IRQ_MODE_SINGLE, isc,
+                              &iib))
+                    break;

AFAIU this code is VFIO interpretation specific code and facility 12 is a precondition for it, so I think this break will never occur. If I am right we should not test the return value which will make the code clearer.

Yep, you are correct; we can just ignore the return value here.


+                first = found = false;
+            } else {
+                /* Interrupts on and all bits processed */
+                break;
+            }

May be add a comment: "rescan after re-enabling interrupts"

OK


+            found = false;
+            si = 0;
+            continue;
+        }
+        found = true;
+        aen_host_forward(si);
+    }
+
+    spin_unlock_irqrestore(&aift->gait_lock, flags);
+}
+
  static void gib_alert_irq_handler(struct airq_struct *airq,
                    struct tpi_info *tpi_info)
  {
+    struct tpi_adapter_info *info = (struct tpi_adapter_info *)tpi_info;
+
      inc_irq_stat(IRQIO_GAL);
-    process_gib_alert_list();
+
+    if (IS_ENABLED(CONFIG_PCI) && (info->forward || info->error)) {
+        aen_process_gait(info->isc);
+        if (info->aism != 0)
+            process_gib_alert_list();
+    } else
+        process_gib_alert_list();

NIT: I think we need braces around this statement

OK


  }
  static struct airq_struct gib_alert_irq = {
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 01dc3f6883d0..ab8b56deed11 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -65,7 +65,8 @@ const struct _kvm_stats_desc kvm_vm_stats_desc[] = {
      STATS_DESC_COUNTER(VM, inject_float_mchk),
      STATS_DESC_COUNTER(VM, inject_pfault_done),
      STATS_DESC_COUNTER(VM, inject_service_signal),
-    STATS_DESC_COUNTER(VM, inject_virtio)
+    STATS_DESC_COUNTER(VM, inject_virtio),
+    STATS_DESC_COUNTER(VM, aen_forward)
  };
  const struct kvm_stats_header kvm_vm_stats_header = {
diff --git a/arch/s390/kvm/pci.h b/arch/s390/kvm/pci.h
index b2000ed7b8c3..387b637863c9 100644
--- a/arch/s390/kvm/pci.h
+++ b/arch/s390/kvm/pci.h
@@ -12,6 +12,7 @@
  #include <linux/pci.h>
  #include <linux/mutex.h>
+#include <linux/kvm_host.h>
  #include <asm/airq.h>
  #include <asm/kvm_pci.h>
@@ -34,6 +35,14 @@ struct zpci_aift {
  extern struct zpci_aift *aift;
+static inline struct kvm *kvm_s390_pci_si_to_kvm(struct zpci_aift *aift,
+                         unsigned long si)
+{
+    if (!IS_ENABLED(CONFIG_PCI) || aift->kzdev == 0 || aift->kzdev[si] == 0)

Shouldn't it be better CONFIG_VFIO_PCI ?

While it's true that we can't be doing interpretation without CONFIG_VFIO_PCI=y|m, the reason I'm using CONFIG_PCI here and elsewhere in the code is because CONFIG_PCI is what is being used to determine whether or not we build arch/s390/kvm/pci.o in patch 14 (and thus whether or not the aift exists) -- And the reason we use this is because this is where the code dependencies exist (examples include ZPCI_NR_DEVICES, the AEN pieces that must be preserved over KVM module remove/insert in patch 15)

If we for some reason have a case where CONFIG_KVM=y|m && CONFIG_PCI=y|m && CONFIG_VFIO_PCI=n, this will still work: aift and aift->kzdev will exist (kvm/pci.o is linked) but we will never actually drive this routine anyway because we'll never register a device for AEN forwarding without CONFIG_VFIO_PCI.






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