Introduce a new pci_preserve_config field in virt machine state which
allows the generation of DSM #5. This field is only set if accel SMMU
is instantiated.

In a subsequent patch, SMMUv3 accel mode will make use of IORT RMR nodes
to enable nested translation of MSI doorbell addresses. IORT RMR requires
_DSM #5 to be set for the PCI host bridge so that the Guest kernel
preserves the PCI boot configuration.

Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
Tested-by: Zhangfei Gao <zhangfei.gao@linaro.org>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Tested-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Shameer Kolothum <skolothumtho@nvidia.com>
---
 hw/arm/virt-acpi-build.c | 8 ++++++++
 hw/arm/virt.c            | 1 +
 include/hw/arm/virt.h    | 1 +
 3 files changed, 10 insertions(+)

diff --git a/hw/arm/virt-acpi-build.c b/hw/arm/virt-acpi-build.c
index 03b4342574..9032a5df1c 100644
--- a/hw/arm/virt-acpi-build.c
+++ b/hw/arm/virt-acpi-build.c
@@ -164,6 +164,14 @@ static void acpi_dsdt_add_pci(Aml *scope, const MemMapEntry *memmap,
         .pci_native_hotplug = !acpi_pcihp,
     };
 
+    /*
+     * Accel SMMU requires RMRs for MSI 1-1 mapping, which require _DSM
+     * function 5 (_DSM for Preserving PCI Boot Configurations).
+     */
+    if (vms->pci_preserve_config) {
+        cfg.preserve_config = true;
+    }
+
     if (vms->highmem_mmio) {
         cfg.mmio64 = memmap[VIRT_HIGH_PCIE_MMIO];
     }
diff --git a/hw/arm/virt.c b/hw/arm/virt.c
index 1bbc5d94db..987bfba7d7 100644
--- a/hw/arm/virt.c
+++ b/hw/arm/virt.c
@@ -3080,6 +3080,7 @@ static void virt_machine_device_pre_plug_cb(HotplugHandler *hotplug_dev,
             }
             object_property_set_uint(OBJECT(dev), "msi-gpa", db_start,
                                      &error_abort);
+            vms->pci_preserve_config = true;
         }
     }
 }
diff --git a/include/hw/arm/virt.h b/include/hw/arm/virt.h
index 5907d41dbb..3b382bdf49 100644
--- a/include/hw/arm/virt.h
+++ b/include/hw/arm/virt.h
@@ -182,6 +182,7 @@ struct VirtMachineState {
     bool legacy_smmuv3_present;
     MemoryRegion *sysmem;
     MemoryRegion *secure_sysmem;
+    bool pci_preserve_config;
 };
 
 #define VIRT_ECAM_ID(high) (high ? VIRT_HIGH_PCIE_ECAM : VIRT_PCIE_ECAM)
-- 
2.43.0