[Qemu-devel] [PATCH v1 3/5] s390x/intc: Emulate Adapter Interrupt Suppression

[Pierre Morel]

Emulate the Adapter Interrupt Suppression in the KVM FLIC interface when
the kernel does not support AIS.

When the kernel KVM does not support AIS, we can not support VFIO PCI
devices but we still can support emulated devices if we emulate AIS
inside QEMU.
Let's emulate AIS, allowing to use emulated PCI devices without KVM AIS
support.

Signed-off-by: Pierre Morel <address@hidden>
---
 hw/intc/s390_flic.c     |  3 +-
 hw/intc/s390_flic_kvm.c | 76 ++++++++++++++++++++++++++++++++++++++++---------
 2 files changed, 64 insertions(+), 15 deletions(-)

diff --git a/hw/intc/s390_flic.c b/hw/intc/s390_flic.c
index 6eaf178..33a7cde 100644
--- a/hw/intc/s390_flic.c
+++ b/hw/intc/s390_flic.c
@@ -185,8 +185,7 @@ static void s390_flic_common_realize(DeviceState *dev, 
Error **errp)
                    " (%d > %d)", max_batch, ADAPTER_ROUTES_MAX_GSI);
         return;
     }
-
-    fs->ais_supported = s390_has_feat(S390_FEAT_ADAPTER_INT_SUPPRESSION);
+    fs->ais_supported = false;
 }
 
 static void s390_flic_class_init(ObjectClass *oc, void *data)
diff --git a/hw/intc/s390_flic_kvm.c b/hw/intc/s390_flic_kvm.c
index 7ead17a..fd1aa22 100644
--- a/hw/intc/s390_flic_kvm.c
+++ b/hw/intc/s390_flic_kvm.c
@@ -33,6 +33,8 @@ typedef struct KVMS390FLICState {
 
     uint32_t fd;
     bool clear_io_supported;
+    uint8_t simm;
+    uint8_t nimm;
 } KVMS390FLICState;
 
 DeviceState *s390_flic_kvm_create(void)
@@ -164,11 +166,24 @@ static int kvm_s390_modify_ais_mode(S390FLICState *fs, 
uint8_t isc,
         .addr = (uint64_t)&req,
     };
 
-    if (!fs->ais_supported) {
-        return -ENOSYS;
+    if (fs->ais_supported) {
+        return ioctl(flic->fd, KVM_SET_DEVICE_ATTR, &attr) ? -errno : 0;
     }
 
-    return ioctl(flic->fd, KVM_SET_DEVICE_ATTR, &attr) ? -errno : 0;
+    /* Kernel does not support AIS, emulate it here */
+    switch (mode) {
+    case SIC_IRQ_MODE_ALL:
+        flic->simm &= ~AIS_MODE_MASK(isc);
+        flic->nimm &= ~AIS_MODE_MASK(isc);
+        break;
+    case SIC_IRQ_MODE_SINGLE:
+        flic->simm |= AIS_MODE_MASK(isc);
+        flic->nimm &= ~AIS_MODE_MASK(isc);
+        break;
+    default:
+        return -EINVAL;
+    }
+    return 0;
 }
 
 static int kvm_s390_inject_airq(S390FLICState *fs, uint8_t type,
@@ -180,12 +195,23 @@ static int kvm_s390_inject_airq(S390FLICState *fs, 
uint8_t type,
         .group = KVM_DEV_FLIC_AIRQ_INJECT,
         .attr = id,
     };
+    uint32_t io_int_word = (isc << 27) | IO_INT_WORD_AI;
 
-    if (!fs->ais_supported) {
-        return -ENOSYS;
+    if (fs->ais_supported) {
+        return ioctl(flic->fd, KVM_SET_DEVICE_ATTR, &attr) ? -errno : 0;
     }
 
-    return ioctl(flic->fd, KVM_SET_DEVICE_ATTR, &attr) ? -errno : 0;
+    /* Kernel does not support AIS, emulate it here */
+    if (flags && (flic->nimm & AIS_MODE_MASK(isc))) {
+        return 0;
+    }
+
+    s390_io_interrupt(0, 0, 0, io_int_word);
+
+    if (flags && (flic->simm & AIS_MODE_MASK(isc))) {
+        flic->nimm |= AIS_MODE_MASK(isc);
+    }
+    return 0;
 }
 
 /**
@@ -557,6 +583,32 @@ static void kvm_s390_flic_realize(DeviceState *dev, Error 
**errp)
     test_attr.group = KVM_DEV_FLIC_CLEAR_IO_IRQ;
     flic_state->clear_io_supported = !ioctl(flic_state->fd,
                                             KVM_HAS_DEVICE_ATTR, test_attr);
+    /* To support ais we need all these three FLIC attributes */
+    test_attr.group = KVM_DEV_FLIC_AISM;
+    ret = !ioctl(flic_state->fd, KVM_HAS_DEVICE_ATTR, test_attr);
+    flic_state->parent_obj.ais_supported &= ret;
+
+    test_attr.group = KVM_DEV_FLIC_AIRQ_INJECT;
+    ret = !ioctl(flic_state->fd, KVM_HAS_DEVICE_ATTR, test_attr);
+    flic_state->parent_obj.ais_supported &= ret;
+
+    test_attr.group = KVM_DEV_FLIC_AISM_ALL;
+    ret &= !ioctl(flic_state->fd, KVM_HAS_DEVICE_ATTR, test_attr);
+    flic_state->parent_obj.ais_supported &= ret;
+
+    /* For buggy kernels we need to really test that the attribute is 
supported */
+    {
+        struct kvm_s390_ais_req req = {
+            .mode = SIC_IRQ_MODE_ALL,
+        };
+        struct kvm_device_attr attr = {
+            .group = KVM_DEV_FLIC_AISM,
+            .addr = (uint64_t)&req,
+        };
+        ret = !ioctl(flic_state->fd, KVM_SET_DEVICE_ATTR, &attr);
+    }
+    flic_state->parent_obj.ais_supported &= ret;
+
     return;
 fail:
     error_propagate(errp, errp_local);
@@ -578,13 +630,11 @@ static void kvm_s390_flic_reset(DeviceState *dev)
 
     flic_disable_wait_pfault(flic);
 
-    if (fs->ais_supported) {
-        for (isc = 0; isc <= MAX_ISC; isc++) {
-            rc = kvm_s390_modify_ais_mode(fs, isc, SIC_IRQ_MODE_ALL);
-            if (rc) {
-                error_report("Failed to reset ais mode for isc %d: %s",
-                             isc, strerror(-rc));
-            }
+    for (isc = 0; isc <= MAX_ISC; isc++) {
+        rc = kvm_s390_modify_ais_mode(fs, isc, SIC_IRQ_MODE_ALL);
+        if (rc) {
+            error_report("Failed to reset ais mode for isc %d: %s",
+                         isc, strerror(-rc));
         }
     }
 
-- 
2.3.0