Report when in-vm kernel supports memory hotplug

QubesOS/qubes-issues#7956

qubes-rpc/post-install.d/10-qubes-core-agent-memory-hotplug.sh

@@ -0,0 +1,22 @@
+#!/bin/sh
+
+# detect if in-vm kernel supports memory hotplug
+# report for newest kernel in /boot, regardless of which one is running
+
+shopt -s nullglob
+
+mem_hotplug_supported=
+# look for first kernel with matching config
+for kernel in $(ls /boot/vmlinuz-* | sort -rV); do
+    kver="${kernel#*/vmlinuz-}"
+    if [ -e "/boot/config-$kver" ]; then
+        config="/boot/config-$kver"
+        if grep -q CONFIG_XEN_BALLOON_MEMORY_HOTPLUG=y "$config"; then
+            mem_hotplug_supported=1
+        fi
+        break
+    fi
+done
+
+# report both positive and negative info
+qvm-features-request supported-feature.memory-hotplug="$mem_hotplug_supported"