Default to UEFI (non-SB) on x86_64

There's some momentum around e.g. UKI
https://github.com/uapi-group/specifications/blob/main/specs/unified_kernel_image.md

I think it's about time to flip our default to be UEFI instead
of BIOS.

(But, we obviously still do need to care about bios...and
 we should e.g. be running at least a subset of our tests
 acrosss that too)

Also while we're here, make the implementation here have the
default for firmware be the empty string `""` instead of `bios`,
which doesn't really apply on e.g. ppc64le/s390x.

mantle/cmd/kola/options.go

@@ -210,8 +210,6 @@ func syncOptionsImpl(useCosa bool) error {
 			kola.QEMUOptions.Firmware = "uefi"
 		} else if kola.Options.CosaBuildArch == "x86_64" && kola.QEMUOptions.Native4k {
 			kola.QEMUOptions.Firmware = "uefi"
-		} else {
-			kola.QEMUOptions.Firmware = "bios"
 		}
 	}
 

mantle/platform/qemu.go

@@ -449,7 +449,7 @@ type QemuBuilder struct {
 // NewQemuBuilder creates a new build for QEMU with default settings.
 func NewQemuBuilder() *QemuBuilder {
 	ret := QemuBuilder{
-		Firmware:  "bios",
+		Firmware:  "",
 		Swtpm:     true,
 		Pdeathsig: true,
 		Argv:      []string{},
@@ -1394,8 +1394,15 @@ func (builder *QemuBuilder) Exec() (*QemuInstance, error) {
 	}
 	argv = append(argv, "-smp", fmt.Sprintf("%d", builder.Processors))
 
+	if builder.Firmware == "" {
+		switch coreosarch.CurrentRpmArch() {
+		case "x86_64", "aarch64":
+			builder.Firmware = "uefi"
+		}
+	}
+
 	switch builder.Firmware {
-	case "bios":
+	case "":
 		break
 	case "uefi":
 		if err := builder.setupUefi(false); err != nil {

src/cmd-kola

@@ -10,7 +10,7 @@ import sys
 # Just test these boot to start with.  In the future we should at least
 # do ostree upgrades with uefi etc.  But we don't really need the *full*
 # suite...if podman somehow broke with nvme or uefi I'd be amazed and impressed.
-BASIC_SCENARIOS = ["nvme=true", "firmware=uefi"]
+BASIC_SCENARIOS = ["nvme=true", "firmware=bios"]
 BASIC_SCENARIOS_SECURE_BOOT = ["firmware=uefi-secure"]
 arch = platform.machine()