kvm: require KVM_CAP_SIGNAL_MSI

This was introduced in KVM in Linux 3.5, we can require it unconditionally
in kvm_irqchip_send_msi().  However, not all architectures have to implement
it so check it only in x86, the only architecture that ever had MSI injection
but not KVM_CAP_SIGNAL_MSI.

ARM uses it to detect the presence of the ITS emulation in the kernel,
introduced in Linux 4.8.  Assume that it's there and possibly fail when
realizing the arm-its-kvm device.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

accel/kvm/kvm-all.c

@@ -99,7 +99,6 @@ bool kvm_gsi_direct_mapping;
 bool kvm_allowed;
 bool kvm_readonly_mem_allowed;
 bool kvm_vm_attributes_allowed;
-bool kvm_direct_msi_allowed;
 bool kvm_ioeventfd_any_length_allowed;
 bool kvm_msi_use_devid;
 bool kvm_has_guest_debug;
@@ -1848,7 +1847,7 @@ static void clear_gsi(KVMState *s, unsigned int gsi)
 
 void kvm_init_irq_routing(KVMState *s)
 {
-    int gsi_count, i;
+    int gsi_count;
 
     gsi_count = kvm_check_extension(s, KVM_CAP_IRQ_ROUTING) - 1;
     if (gsi_count > 0) {
@@ -1860,12 +1859,6 @@ void kvm_init_irq_routing(KVMState *s)
     s->irq_routes = g_malloc0(sizeof(*s->irq_routes));
     s->nr_allocated_irq_routes = 0;
 
-    if (!kvm_direct_msi_allowed) {
-        for (i = 0; i < KVM_MSI_HASHTAB_SIZE; i++) {
-            QTAILQ_INIT(&s->msi_hashtab[i]);
-        }
-    }
-
     kvm_arch_init_irq_routing(s);
 }
 
@@ -1985,41 +1978,10 @@ void kvm_irqchip_change_notify(void)
     notifier_list_notify(&kvm_irqchip_change_notifiers, NULL);
 }
 
-static unsigned int kvm_hash_msi(uint32_t data)
-{
-    /* This is optimized for IA32 MSI layout. However, no other arch shall
-     * repeat the mistake of not providing a direct MSI injection API. */
-    return data & 0xff;
-}
-
-static void kvm_flush_dynamic_msi_routes(KVMState *s)
-{
-    KVMMSIRoute *route, *next;
-    unsigned int hash;
-
-    for (hash = 0; hash < KVM_MSI_HASHTAB_SIZE; hash++) {
-        QTAILQ_FOREACH_SAFE(route, &s->msi_hashtab[hash], entry, next) {
-            kvm_irqchip_release_virq(s, route->kroute.gsi);
-            QTAILQ_REMOVE(&s->msi_hashtab[hash], route, entry);
-            g_free(route);
-        }
-    }
-}
-
 static int kvm_irqchip_get_virq(KVMState *s)
 {
     int next_virq;
 
-    /*
-     * PIC and IOAPIC share the first 16 GSI numbers, thus the available
-     * GSI numbers are more than the number of IRQ route. Allocating a GSI
-     * number can succeed even though a new route entry cannot be added.
-     * When this happens, flush dynamic MSI entries to free IRQ route entries.
-     */
-    if (!kvm_direct_msi_allowed && s->irq_routes->nr == s->gsi_count) {
-        kvm_flush_dynamic_msi_routes(s);
-    }
-
     /* Return the lowest unused GSI in the bitmap */
     next_virq = find_first_zero_bit(s->used_gsi_bitmap, s->gsi_count);
     if (next_virq >= s->gsi_count) {
@@ -2029,63 +1991,17 @@ static int kvm_irqchip_get_virq(KVMState *s)
     }
 }
 
-static KVMMSIRoute *kvm_lookup_msi_route(KVMState *s, MSIMessage msg)
-{
-    unsigned int hash = kvm_hash_msi(msg.data);
-    KVMMSIRoute *route;
-
-    QTAILQ_FOREACH(route, &s->msi_hashtab[hash], entry) {
-        if (route->kroute.u.msi.address_lo == (uint32_t)msg.address &&
-            route->kroute.u.msi.address_hi == (msg.address >> 32) &&
-            route->kroute.u.msi.data == le32_to_cpu(msg.data)) {
-            return route;
-        }
-    }
-    return NULL;
-}
-
 int kvm_irqchip_send_msi(KVMState *s, MSIMessage msg)
 {
     struct kvm_msi msi;
-    KVMMSIRoute *route;
-
-    if (kvm_direct_msi_allowed) {
-        msi.address_lo = (uint32_t)msg.address;
-        msi.address_hi = msg.address >> 32;
-        msi.data = le32_to_cpu(msg.data);
-        msi.flags = 0;
-        memset(msi.pad, 0, sizeof(msi.pad));
-
-        return kvm_vm_ioctl(s, KVM_SIGNAL_MSI, &msi);
-    }
-
-    route = kvm_lookup_msi_route(s, msg);
-    if (!route) {
-        int virq;
 
-        virq = kvm_irqchip_get_virq(s);
-        if (virq < 0) {
-            return virq;
-        }
-
-        route = g_new0(KVMMSIRoute, 1);
-        route->kroute.gsi = virq;
-        route->kroute.type = KVM_IRQ_ROUTING_MSI;
-        route->kroute.flags = 0;
-        route->kroute.u.msi.address_lo = (uint32_t)msg.address;
-        route->kroute.u.msi.address_hi = msg.address >> 32;
-        route->kroute.u.msi.data = le32_to_cpu(msg.data);
-
-        kvm_add_routing_entry(s, &route->kroute);
-        kvm_irqchip_commit_routes(s);
-
-        QTAILQ_INSERT_TAIL(&s->msi_hashtab[kvm_hash_msi(msg.data)], route,
-                           entry);
-    }
+    msi.address_lo = (uint32_t)msg.address;
+    msi.address_hi = msg.address >> 32;
+    msi.data = le32_to_cpu(msg.data);
+    msi.flags = 0;
+    memset(msi.pad, 0, sizeof(msi.pad));
 
-    assert(route->kroute.type == KVM_IRQ_ROUTING_MSI);
-
-    return kvm_set_irq(s, route->kroute.gsi, 1);
+    return kvm_vm_ioctl(s, KVM_SIGNAL_MSI, &msi);
 }
 
 int kvm_irqchip_add_msi_route(KVMRouteChange *c, int vector, PCIDevice *dev)
@@ -2660,10 +2576,6 @@ static int kvm_init(MachineState *ms)
 
     s->max_nested_state_len = kvm_check_extension(s, KVM_CAP_NESTED_STATE);
 
-#ifdef KVM_CAP_IRQ_ROUTING
-    kvm_direct_msi_allowed = (kvm_check_extension(s, KVM_CAP_SIGNAL_MSI) > 0);
-#endif
-
     s->intx_set_mask = kvm_check_extension(s, KVM_CAP_PCI_2_3);
 
     s->irq_set_ioctl = KVM_IRQ_LINE;

accel/stubs/kvm-stub.c

@@ -27,7 +27,6 @@ bool kvm_allowed;
 bool kvm_readonly_mem_allowed;
 bool kvm_ioeventfd_any_length_allowed;
 bool kvm_msi_use_devid;
-bool kvm_direct_msi_allowed;
 
 void kvm_flush_coalesced_mmio_buffer(void)
 {

hw/intc/arm_gicv3_its_common.c

@@ -163,8 +163,7 @@ type_init(gicv3_its_common_register_types)
 const char *its_class_name(void)
 {
     if (kvm_irqchip_in_kernel()) {
-        /* KVM implementation requires this capability */
-        return kvm_direct_msi_enabled() ? "arm-its-kvm" : NULL;
+        return "arm-its-kvm";
     } else {
         /* Software emulation based model */
         return "arm-gicv3-its";

include/sysemu/kvm.h

@@ -43,7 +43,6 @@ extern bool kvm_msi_via_irqfd_allowed;
 extern bool kvm_gsi_routing_allowed;
 extern bool kvm_gsi_direct_mapping;
 extern bool kvm_readonly_mem_allowed;
-extern bool kvm_direct_msi_allowed;
 extern bool kvm_ioeventfd_any_length_allowed;
 extern bool kvm_msi_use_devid;
 
@@ -147,13 +146,6 @@ extern bool kvm_msi_use_devid;
  */
 #define kvm_readonly_mem_enabled() (kvm_readonly_mem_allowed)
 
-/**
- * kvm_direct_msi_enabled:
- *
- * Returns: true if KVM allows direct MSI injection.
- */
-#define kvm_direct_msi_enabled() (kvm_direct_msi_allowed)
-
 /**
  * kvm_ioeventfd_any_length_enabled:
  * Returns: true if KVM allows any length io eventfd.
@@ -181,7 +173,6 @@ extern bool kvm_msi_use_devid;
 #define kvm_gsi_routing_allowed() (false)
 #define kvm_gsi_direct_mapping() (false)
 #define kvm_readonly_mem_enabled() (false)
-#define kvm_direct_msi_enabled() (false)
 #define kvm_ioeventfd_any_length_enabled() (false)
 #define kvm_msi_devid_required() (false)
 

include/sysemu/kvm_int.h

@@ -103,7 +103,6 @@ struct KVMState
     int nr_allocated_irq_routes;
     unsigned long *used_gsi_bitmap;
     unsigned int gsi_count;
-    QTAILQ_HEAD(, KVMMSIRoute) msi_hashtab[KVM_MSI_HASHTAB_SIZE];
 #endif
     KVMMemoryListener memory_listener;
     QLIST_HEAD(, KVMParkedVcpu) kvm_parked_vcpus;

target/i386/kvm/kvm.c

@@ -91,6 +91,7 @@ const KVMCapabilityInfo kvm_arch_required_capabilities[] = {
     KVM_CAP_INFO(SET_TSS_ADDR),
     KVM_CAP_INFO(EXT_CPUID),
     KVM_CAP_INFO(MP_STATE),
+    KVM_CAP_INFO(SIGNAL_MSI),
     KVM_CAP_LAST_INFO
 };