[RFC PATCH v2 4/5] hw/arm/virt: export fixed BAR metadata via fw_cfg

[Tushar Dave <tdave@nvidia.com>]

Export fixed BAR metadata from the virt machine through the
"etc/fixed-bars" fw_cfg file during machine initialization.

Fixed BAR placement requires firmware to preserve the PCI resource
configuration established by QEMU. ACPI provides this via the PCI
boot configuration preservation mechanism, _DSM function 5.

Reject fixed BAR configuration when ACPI is disabled, and request PCI
boot configuration preservation when ACPI is enabled.

Signed-off-by: Tushar Dave <tdave@nvidia.com>
---
 hw/arm/virt.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/hw/arm/virt.c b/hw/arm/virt.c
index e7a56e37f7..cb9cd2d25c 100644
--- a/hw/arm/virt.c
+++ b/hw/arm/virt.c
@@ -96,6 +96,7 @@
 #include "hw/cxl/cxl_host.h"
 #include "qemu/guest-random.h"
 #include "hw/watchdog/sbsa_gwdt.h"
+#include "hw/pci/pci-fixed-bar.h"
 
 static GlobalProperty arm_virt_compat_defaults[] = {
     { TYPE_VIRTIO_IOMMU_PCI, "aw-bits", "48" },
@@ -2440,6 +2441,21 @@ void virt_machine_done(Notifier *notifier, void *data)
                                        vms->memmap[VIRT_PLATFORM_BUS].size,
                                        vms->irqmap[VIRT_PLATFORM_BUS]);
     }
+    if (fixed_bars_write_blob(vms->fw_cfg,
+                              vms->memmap[VIRT_PCIE_MMIO].base,
+                              vms->memmap[VIRT_PCIE_MMIO].size,
+                              vms->memmap[VIRT_HIGH_PCIE_MMIO].base,
+                              vms->memmap[VIRT_HIGH_PCIE_MMIO].size)) {
+        if (!virt_is_acpi_enabled(vms)) {
+            error_report("pci-bars: fixed BAR placement requires ACPI to "
+                         "preserve the PCI boot configuration, otherwise "
+                         "these BAR assignments could be reassigned later "
+                         "with no protection");
+            exit(1);
+        }
+        vms->pci_preserve_config = true;
+    }
+
     if (arm_load_dtb(info->dtb_start, info, info->dtb_limit, as, ms, cpu) < 0) {
         exit(1);
     }
-- 
2.34.1