q35: ioapic: add support for emulated IOAPIC IR

This patch translates all IOAPIC interrupts into MSI ones. One pseudo
ioapic address space is added to transfer the MSI message. By default,
it will be system memory address space. When IR is enabled, it will be
IOMMU address space.

Currently, only emulated IOAPIC is supported.

Idea suggested by Jan Kiszka and Rita Sinha in the following patch:

https://lists.gnu.org/archive/html/qemu-devel/2016-03/msg01933.html

Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

3 files changed, 32 insertions, 5 deletions

diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c
index ccfcc69..6ba5520 100644
--- a/hw/i386/intel_iommu.c
+++ b/hw/i386/intel_iommu.c
@@ -28,6 +28,7 @@
 #include "hw/i386/pc.h"
 #include "hw/boards.h"
 #include "hw/i386/x86-iommu.h"
+#include "hw/pci-host/q35.h"
 
 /*#define DEBUG_INTEL_IOMMU*/
 #ifdef DEBUG_INTEL_IOMMU
@@ -2367,7 +2368,8 @@ static AddressSpace *vtd_host_dma_iommu(PCIBus *bus, void *opaque, int devfn)
 
 static void vtd_realize(DeviceState *dev, Error **errp)
 {
-    PCIBus *bus = PC_MACHINE(qdev_get_machine())->bus;
+    PCMachineState *pcms = PC_MACHINE(qdev_get_machine());
+    PCIBus *bus = pcms->bus;
     IntelIOMMUState *s = INTEL_IOMMU_DEVICE(dev);
 
     VTD_DPRINTF(GENERAL, "");
@@ -2383,6 +2385,8 @@ static void vtd_realize(DeviceState *dev, Error **errp)
     vtd_init(s);
     sysbus_mmio_map(SYS_BUS_DEVICE(s), 0, Q35_HOST_BRIDGE_IOMMU_ADDR);
     pci_setup_iommu(bus, vtd_host_dma_iommu, dev);
+    /* Pseudo address space under root PCI bus. */
+    pcms->ioapic_as = vtd_host_dma_iommu(bus, s, Q35_PSEUDO_DEVFN_IOAPIC);
 }
 
 static void vtd_class_init(ObjectClass *klass, void *data)
diff --git a/hw/i386/pc.c b/hw/i386/pc.c
index 719884f..979f36d 100644
--- a/hw/i386/pc.c
+++ b/hw/i386/pc.c
@@ -1475,6 +1475,9 @@ void pc_memory_init(PCMachineState *pcms,
         rom_add_option(option_rom[i].name, option_rom[i].bootindex);
     }
     pcms->fw_cfg = fw_cfg;
+
+    /* Init default IOAPIC address space */
+    pcms->ioapic_as = &address_space_memory;
 }
 
 qemu_irq pc_allocate_cpu_irq(void)
diff --git a/hw/intc/ioapic.c b/hw/intc/ioapic.c
index 273bb08..36dd42a 100644
--- a/hw/intc/ioapic.c
+++ b/hw/intc/ioapic.c
@@ -29,6 +29,8 @@
 #include "hw/i386/ioapic_internal.h"
 #include "include/hw/pci/msi.h"
 #include "sysemu/kvm.h"
+#include "target-i386/cpu.h"
+#include "hw/i386/apic-msidef.h"
 
 //#define DEBUG_IOAPIC
 
@@ -50,13 +52,15 @@ extern int ioapic_no;
 
 static void ioapic_service(IOAPICCommonState *s)
 {
+    AddressSpace *ioapic_as = PC_MACHINE(qdev_get_machine())->ioapic_as;
+    uint32_t addr, data;
     uint8_t i;
     uint8_t trig_mode;
     uint8_t vector;
     uint8_t delivery_mode;
     uint32_t mask;
     uint64_t entry;
-    uint8_t dest;
+    uint16_t dest_idx;
     uint8_t dest_mode;
 
     for (i = 0; i < IOAPIC_NUM_PINS; i++) {
@@ -67,7 +71,14 @@ static void ioapic_service(IOAPICCommonState *s)
             entry = s->ioredtbl[i];
             if (!(entry & IOAPIC_LVT_MASKED)) {
                 trig_mode = ((entry >> IOAPIC_LVT_TRIGGER_MODE_SHIFT) & 1);
-                dest = entry >> IOAPIC_LVT_DEST_SHIFT;
+                /*
+                 * By default, this would be dest_id[8] +
+                 * reserved[8]. When IR is enabled, this would be
+                 * interrupt_index[15] + interrupt_format[1]. This
+                 * field never means anything, but only used to
+                 * generate corresponding MSI.
+                 */
+                dest_idx = entry >> IOAPIC_LVT_DEST_IDX_SHIFT;
                 dest_mode = (entry >> IOAPIC_LVT_DEST_MODE_SHIFT) & 1;
                 delivery_mode =
                     (entry >> IOAPIC_LVT_DELIV_MODE_SHIFT) & IOAPIC_DM_MASK;
@@ -97,8 +108,17 @@ static void ioapic_service(IOAPICCommonState *s)
 #else
                 (void)coalesce;
 #endif
-                apic_deliver_irq(dest, dest_mode, delivery_mode, vector,
-                                 trig_mode);
+                /* No matter whether IR is enabled, we translate
+                 * the IOAPIC message into a MSI one, and its
+                 * address space will decide whether we need a
+                 * translation. */
+                addr = APIC_DEFAULT_ADDRESS | \
+                    (dest_idx << MSI_ADDR_DEST_IDX_SHIFT) |
+                    (dest_mode << MSI_ADDR_DEST_MODE_SHIFT);
+                data = (vector << MSI_DATA_VECTOR_SHIFT) |
+                    (trig_mode << MSI_DATA_TRIGGER_SHIFT) |
+                    (delivery_mode << MSI_DATA_DELIVERY_MODE_SHIFT);
+                stl_le_phys(ioapic_as, addr, data);
             }
         }
     }