test(kvm): the video model of an ARM guest comes from the hypervisor

The video models of a machine type come from the emulator build, not from the
architecture. On one host libvirt reports virtio for a riscv64 virt machine and
not for an aarch64 one, because that aarch64 emulator carries no virtio-gpu
device, and `virsh define` on an aarch64 virt domain answers "domain
configuration does not support video model 'virtio'".

A hard-coded model is therefore wrong on one host or the other. The test gives
the domain builder a hypervisor connection that answers a domain capabilities
document, and asserts the model it picks: virtio when the hypervisor offers it,
vga when it does not, and vga when there is no connection or no video section.
vm.vidmodel keeps its own answer.

Three of the new assertions fail on the unfixed tree.

Signed-off-by: Daniel Hilst <392820+dhilst@users.noreply.github.com>

xCAT-test/unit/kvm_guest_arch.t

@@ -49,11 +49,13 @@ sub domain_xml {
                     cpus   => 4,
                     (defined $opt{othersettings}
                           ? (othersettings => $opt{othersettings}) : ()),
+                    (defined $opt{vidmodel} ? (vidmodel => $opt{vidmodel}) : ()),
             } ]
         },
         nodetype => { cn1 => [ { arch => $guest_arch, os => 'rocky10.2' } ] },
         hyp1     => { cpumodel => $hyp_cpumodel, cputype => $opt{cputype} },
     };
+    local $KVMArch::hypconn    = $opt{hypconn};
     local $KVMArch::updatetable = {};
     my $xml = KVMArch::build_xmldesc('cn1');
     die("build_xmldesc returned no XML for $guest_arch on $hyp_cpumodel")
@@ -61,6 +63,51 @@ sub domain_xml {
     return $xml;
 }
 
+# A hypervisor connection that answers one domain capabilities document.
+{
+
+    package CapsConn;
+    sub new { my ($class, $xml) = @_; return bless { xml => $xml }, $class; }
+    sub get_domain_capabilities { return $_[0]->{xml}; }
+}
+
+# The modelType enum of an aarch64 virt machine, as libvirt 11.10 reports it on a host whose
+# aarch64 emulator carries no virtio-gpu device. libvirt refuses a domain that names virtio
+# there.
+my $caps_without_virtio = <<'CAPS';
+<domainCapabilities>
+  <arch>aarch64</arch>
+  <devices>
+    <video supported='yes'>
+      <enum name='modelType'>
+        <value>vga</value>
+        <value>cirrus</value>
+        <value>none</value>
+        <value>bochs</value>
+        <value>ramfb</value>
+      </enum>
+    </video>
+  </devices>
+</domainCapabilities>
+CAPS
+
+my $caps_with_virtio = <<'CAPS';
+<domainCapabilities>
+  <arch>aarch64</arch>
+  <devices>
+    <video supported='yes'>
+      <enum name='modelType'>
+        <value>vga</value>
+        <value>virtio</value>
+        <value>ramfb</value>
+      </enum>
+    </video>
+  </devices>
+</domainCapabilities>
+CAPS
+
+my $caps_without_video = "<domainCapabilities><arch>aarch64</arch></domainCapabilities>\n";
+
 sub os_type_element {
     my ($xml) = @_;
     my ($attrs) = $xml =~ m{<type\b([^>]*)>hvm</type>}s;
@@ -99,8 +146,8 @@ like($arm, qr/<os\b[^>]*\bfirmware="efi"/,
     'an aarch64 virt guest boots UEFI');
 like($arm, qr{<cpu\b[^>]*\bmode="custom"[^>]*>\s*<model>cortex-a57</model>}s,
     'an emulated aarch64 guest states cortex-a57 as a custom CPU model');
-like($arm, qr/<model\b[^>]*\btype="virtio"/,
-    'an aarch64 virt guest takes the virtio video model, as a riscv64 virt guest does');
+like($arm, qr/<model\b[^>]*\btype="vga"/,
+    'an aarch64 guest falls back to vga when no hypervisor states its video models');
 unlike($arm, qr/<(?:pae|acpi|apic)\b/,
     'pae, acpi and apic are x86 features and are left out of an aarch64 guest');
 unlike($arm, qr/<bios\b/,
@@ -108,6 +155,29 @@ unlike($arm, qr/<bios\b/,
 unlike($arm, qr/<input\b/,
     'the aarch64 virt machine has no USB controller, so it gets no USB tablet');
 
+# The video models of a machine type come from the emulator build, not from the architecture.
+# libvirt refuses a domain that names a model the emulator of the hypervisor has no device
+# for, so the model comes from the capabilities of that hypervisor.
+my $arm_no_virtio =
+  domain_xml('aarch64', 'x86_64', hypconn => CapsConn->new($caps_without_virtio));
+like($arm_no_virtio, qr/<model\b[^>]*\btype="vga"/,
+    'an aarch64 guest takes vga from a hypervisor that offers no virtio video model');
+
+my $arm_virtio =
+  domain_xml('aarch64', 'x86_64', hypconn => CapsConn->new($caps_with_virtio));
+like($arm_virtio, qr/<model\b[^>]*\btype="virtio"/,
+    'an aarch64 guest takes virtio from a hypervisor that offers it');
+
+my $arm_no_video =
+  domain_xml('aarch64', 'x86_64', hypconn => CapsConn->new($caps_without_video));
+like($arm_no_video, qr/<model\b[^>]*\btype="vga"/,
+    'an aarch64 guest falls back to vga when the hypervisor states no video models');
+
+my $arm_vidmodel = domain_xml('aarch64', 'x86_64',
+    hypconn => CapsConn->new($caps_with_virtio), vidmodel => 'ramfb');
+like($arm_vidmodel, qr/<model\b[^>]*\btype="ramfb"/,
+    'vm.vidmodel still names the video model of an aarch64 guest');
+
 # An aarch64 node on an aarch64 hypervisor. The guest arch is the host arch, so the domain runs
 # under KVM. KVM on ARM runs the host CPU and no other model, and libvirt reports
 # host-passthrough as unsupported for an emulated aarch64 domain.