[RFC 2/2] q35: add virtio-mmio slots

[Oliver Steffen <osteffen@redhat.com>]

From: Gerd Hoffmann <kraxel@redhat.com>

Add virtio-mmio slots to the q35 machine model, intended to be used by
an SVSM.

Disabled by default, enable using '-machine q35,x-svsm-virtio-mmio=on'.

When enabled it is possible to plug up to 4 virtio devices into the
slots virtio-mmio using '-device virtio-${kind}-device'.

The devices can be found at base address 0xfef00000, each slot on a
separate page.  No IRQ is wired up, the SVSM has to drive the devices
in polling mode.

The base addresses are communicated to the SVSM via the etc/hardware-info
fw_cfg file.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Oliver Steffen <osteffen@redhat.com>
---
 hw/i386/pc.c         | 18 +++++++++++++++++-
 hw/i386/pc_q35.c     | 15 +++++++++++++++
 include/hw/i386/pc.h |  1 +
 3 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/hw/i386/pc.c b/hw/i386/pc.c
index 432ab288a8..e1dbf8846d 100644
--- a/hw/i386/pc.c
+++ b/hw/i386/pc.c
@@ -1584,6 +1584,21 @@ static void pc_machine_set_smbios_ep(Object *obj, Visitor *v, const char *name,
     visit_type_SmbiosEntryPointType(v, name, &pcms->smbios_entry_point_type, errp);
 }
 
+static bool pc_machine_get_svsm_virtio_mmio(Object *obj, Error **errp)
+{
+    PCMachineState *pcms = PC_MACHINE(obj);
+
+    return pcms->svsm_virtio_mmio;
+}
+
+static void pc_machine_set_svsm_virtio_mmio(Object *obj, bool value,
+                                            Error **errp)
+{
+    PCMachineState *pcms = PC_MACHINE(obj);
+
+    pcms->svsm_virtio_mmio = value;
+}
+
 static void pc_machine_get_max_ram_below_4g(Object *obj, Visitor *v,
                                             const char *name, void *opaque,
                                             Error **errp)
@@ -1844,7 +1859,8 @@ static void pc_machine_class_init(ObjectClass *oc, const void *data)
                                           "Set IGVM configuration");
 #endif
 
-
+    object_class_property_add_bool(oc, "x-svsm-virtio-mmio",
+        pc_machine_get_svsm_virtio_mmio, pc_machine_set_svsm_virtio_mmio);
 }
 
 static const TypeInfo pc_machine_info = {
diff --git a/hw/i386/pc_q35.c b/hw/i386/pc_q35.c
index cf871cfdad..b8511ae52a 100644
--- a/hw/i386/pc_q35.c
+++ b/hw/i386/pc_q35.c
@@ -60,7 +60,9 @@
 #include "hw/mem/nvdimm.h"
 #include "hw/uefi/var-service-api.h"
 #include "hw/i386/acpi-build.h"
+#include "hw/uefi/hardware-info.h"
 #include "target/i386/cpu.h"
+#include "exec/target_page.h"
 
 /* ICH9 AHCI has 6 ports */
 #define MAX_SATA_PORTS     6
@@ -335,6 +337,19 @@ static void pc_q35_init(MachineState *machine)
         }
     }
 #endif
+
+    if (pcms->svsm_virtio_mmio) {
+        for (int dev = 0; dev < 4; dev++) {
+            HARDWARE_INFO_SIMPLE_DEVICE hwinfo = {
+                .mmio_address = cpu_to_le64(0xfef00000 + dev * TARGET_PAGE_SIZE),
+            };
+            sysbus_create_simple("virtio-mmio", hwinfo.mmio_address,
+                                 /* no irq */ NULL);
+            hardware_info_register(HardwareInfoVirtioMmioSvsm,
+                                   &hwinfo, sizeof(hwinfo));
+        }
+    }
+
 }
 
 #define DEFINE_Q35_MACHINE(major, minor) \
diff --git a/include/hw/i386/pc.h b/include/hw/i386/pc.h
index 79b72c54dd..9c9f947087 100644
--- a/include/hw/i386/pc.h
+++ b/include/hw/i386/pc.h
@@ -51,6 +51,7 @@ typedef struct PCMachineState {
     bool i8042_enabled;
     bool default_bus_bypass_iommu;
     bool fd_bootchk;
+    bool svsm_virtio_mmio;
     uint64_t max_fw_size;
 
     /* ACPI Memory hotplug IO base address */
-- 
2.50.0