kvm: x86: add support for KVM_CAP_SPLIT_IRQCHIP

This patch adds support for split IRQ chip mode. When
KVM_CAP_SPLIT_IRQCHIP is enabled:

    1.) The PIC, PIT, and IOAPIC are implemented in userspace while
    the LAPIC is implemented by KVM.

    2.) The software IOAPIC delivers interrupts to the KVM LAPIC via
    kvm_set_irq. Interrupt delivery is configured via the MSI routing
    table, for which routes are reserved in target-i386/kvm.c then
    configured in hw/intc/ioapic.c

    3.) KVM delivers IOAPIC EOIs via a new exit KVM_EXIT_IOAPIC_EOI,
    which is handled in target-i386/kvm.c and relayed to the software
    IOAPIC via ioapic_eoi_broadcast.

Signed-off-by: Matt Gingell <gingell@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

3 files changed, 43 insertions, 3 deletions

diff --git a/target-i386/cpu.c b/target-i386/cpu.c
index 92f7cc1f7d..0d447b5690 100644
--- a/target-i386/cpu.c
+++ b/target-i386/cpu.c
@@ -2743,7 +2743,7 @@ static void x86_cpu_apic_create(X86CPU *cpu, Error **errp)
     APICCommonState *apic;
     const char *apic_type = "apic";
 
-    if (kvm_irqchip_in_kernel()) {
+    if (kvm_apic_in_kernel()) {
         apic_type = "kvm-apic";
     } else if (xen_enabled()) {
         apic_type = "xen-apic";
diff --git a/target-i386/kvm.c b/target-i386/kvm.c
index 7692b5984d..7b01328ffe 100644
--- a/target-i386/kvm.c
+++ b/target-i386/kvm.c
@@ -39,6 +39,7 @@
 #include "exec/ioport.h"
 #include "standard-headers/asm-x86/hyperv.h"
 #include "hw/pci/pci.h"
+#include "hw/pci/msi.h"
 #include "migration/migration.h"
 #include "exec/memattrs.h"
 
@@ -2597,7 +2598,7 @@ void kvm_arch_pre_run(CPUState *cpu, struct kvm_run *run)
         }
     }
 
-    if (!kvm_irqchip_in_kernel()) {
+    if (!kvm_pic_in_kernel()) {
         qemu_mutex_lock_iothread();
     }
 
@@ -2615,7 +2616,7 @@ void kvm_arch_pre_run(CPUState *cpu, struct kvm_run *run)
         }
     }
 
-    if (!kvm_irqchip_in_kernel()) {
+    if (!kvm_pic_in_kernel()) {
         /* Try to inject an interrupt if the guest can accept it */
         if (run->ready_for_interrupt_injection &&
             (cpu->interrupt_request & CPU_INTERRUPT_HARD) &&
@@ -3017,6 +3018,10 @@ int kvm_arch_handle_exit(CPUState *cs, struct kvm_run *run)
     case KVM_EXIT_HYPERV:
         ret = kvm_hv_handle_exit(cpu, &run->hyperv);
         break;
+    case KVM_EXIT_IOAPIC_EOI:
+        ioapic_eoi_broadcast(run->eoi.vector);
+        ret = 0;
+        break;
     default:
         fprintf(stderr, "KVM: unknown exit reason %d\n", run->exit_reason);
         ret = -1;
@@ -3051,6 +3056,39 @@ void kvm_arch_init_irq_routing(KVMState *s)
      */
     kvm_msi_via_irqfd_allowed = true;
     kvm_gsi_routing_allowed = true;
+
+    if (kvm_irqchip_is_split()) {
+        int i;
+
+        /* If the ioapic is in QEMU and the lapics are in KVM, reserve
+           MSI routes for signaling interrupts to the local apics. */
+        for (i = 0; i < IOAPIC_NUM_PINS; i++) {
+            struct MSIMessage msg = { 0x0, 0x0 };
+            if (kvm_irqchip_add_msi_route(s, msg, NULL) < 0) {
+                error_report("Could not enable split IRQ mode.");
+                exit(1);
+            }
+        }
+    }
+}
+
+int kvm_arch_irqchip_create(MachineState *ms, KVMState *s)
+{
+    int ret;
+    if (machine_kernel_irqchip_split(ms)) {
+        ret = kvm_vm_enable_cap(s, KVM_CAP_SPLIT_IRQCHIP, 0, 24);
+        if (ret) {
+            error_report("Could not enable split irqchip mode: %s\n",
+                         strerror(-ret));
+            exit(1);
+        } else {
+            DPRINTF("Enabled KVM_CAP_SPLIT_IRQCHIP\n");
+            kvm_split_irqchip = true;
+            return 1;
+        }
+    } else {
+        return 0;
+    }
 }
 
 /* Classic KVM device assignment interface. Will remain x86 only. */
diff --git a/target-i386/kvm_i386.h b/target-i386/kvm_i386.h
index c1b312ba2a..42b00af1b1 100644
--- a/target-i386/kvm_i386.h
+++ b/target-i386/kvm_i386.h
@@ -13,6 +13,8 @@
 
 #include "sysemu/kvm.h"
 
+#define kvm_apic_in_kernel() (kvm_irqchip_in_kernel())
+
 bool kvm_allows_irq0_override(void);
 bool kvm_has_smm(void);
 void kvm_synchronize_all_tsc(void);