libvirt: fix PCI-E passthrough configuration after Vagrant removal

The PCI-E passthrough functionality was broken when Vagrant support was
removed. Two issues prevented the passthrough options from appearing in
menuconfig:

1. The check_pciepassthrough_kconfig.sh script was gutted during the
   Vagrant removal and always returned "n", preventing the passthrough
   Kconfig from being detected.

2. The source line for including the generated passthrough Kconfig was
   removed but never updated to the new location.

This commit fixes both issues and additionally improves the user
interface by:

- Restoring the check script to properly detect if the passthrough
  Kconfig file exists
- Adding a proper menu structure with "Enable PCI-E passthrough support"
  boolean option
- Creating a dedicated "Configure PCI-E passthrough" submenu for device
  selection
- Including the assignment strategy choice (manual vs round-robin)

Now users can properly enable and configure PCI-E passthrough through
a clean menu interface instead of having all device options scattered
in the main libvirt menu.

Fixes: 89b7ef8 ("kconfigs: fix Kconfig references after vagrant removal")
Generated-by: Claude AI
Reviewed-by: Chuck Lever <[email protected]>
Signed-off-by: Luis Chamberlain <[email protected]>

Author: mcgrof

kconfigs/Kconfig.libvirt

@@ -462,6 +462,49 @@ config HAVE_LIBVIRT_PCIE_PASSTHROUGH
 	bool
 	default $(shell, scripts/check_pciepassthrough_kconfig.sh passthrough_libvirt.generated)
 
+config KDEVOPS_LIBVIRT_PCIE_PASSTHROUGH
+	bool "Enable PCI-E passthrough support"
+	depends on HAVE_LIBVIRT_PCIE_PASSTHROUGH
+	depends on LIBVIRT
+	depends on LIBVIRT_MACHINE_TYPE_Q35
+	default n
+	help
+	  Enable this to configure PCI-E passthrough of devices from the host
+	  to guest VMs. This requires the q35 machine type and proper IOMMU
+	  configuration on the host.
+
+	  If enabled, you can select which PCI devices to pass through to
+	  which guests in the passthrough configuration menu.
+
+if KDEVOPS_LIBVIRT_PCIE_PASSTHROUGH
+
+menu "Configure PCI-E passthrough"
+
+choice
+	prompt "PCI-E passthrough assignment strategy"
+	default KDEVOPS_LIBVIRT_PCIE_PASSTHROUGH_TYPE_EACH
+
+config KDEVOPS_LIBVIRT_PCIE_PASSTHROUGH_TYPE_EACH
+	bool "Manually assign devices to specific guests"
+	help
+	  This lets you manually specify which PCI device gets assigned to
+	  which specific guest. Each device can be assigned to exactly one
+	  guest.
+
+config KDEVOPS_LIBVIRT_PCIE_PASSTHROUGH_TYPE_ROUNDROBIN
+	bool "Round-robin device assignment"
+	help
+	  Automatically distribute PCI devices among guests in a round-robin
+	  fashion. This is useful when you have multiple similar devices
+	  (like NVMe drives) and want to distribute them evenly.
+
+endchoice
+
+source "Kconfig.passthrough_libvirt.generated"
+
+endmenu
+
+endif # KDEVOPS_LIBVIRT_PCIE_PASSTHROUGH
 
 choice
 	prompt "Machine type to use"

scripts/check_pciepassthrough_kconfig.sh

@@ -1,4 +1,17 @@
 #!/bin/bash
 # SPDX-License-Identifier: copyleft-next-0.3.1
 
-echo n
+# Check if the PCI passthrough Kconfig file exists
+KCONFIG_FILE="$1"
+
+if [ -z "$KCONFIG_FILE" ]; then
+    echo n
+    exit 0
+fi
+
+# Check both with and without Kconfig. prefix
+if [ -f "Kconfig.${KCONFIG_FILE}" ] || [ -f "${KCONFIG_FILE}" ]; then
+    echo y
+else
+    echo n
+fi