diff --git a/docs/kola/external-tests.md b/docs/kola/external-tests.md
index 9c60f9e3cc..ac61dba8aa 100644
--- a/docs/kola/external-tests.md
+++ b/docs/kola/external-tests.md
@@ -191,6 +191,7 @@ Here's an example `kola.json`:
     "platforms": "qemu",
     "tags": "sometagname needs-internet skip-base-checks othertag",
     "requiredTag": "special",
+    "primaryDisk": ["20G:mpath"],
     "additionalDisks": [ "5G" ],
     "minMemory": 4096,
     "minDisk": 15,
@@ -229,7 +230,8 @@ If a test has a `requiredTag`, it is run only if the required tag is specified.
 In the example above, the test would only run if `--tag special` was provided.
 
 The `additionalDisks` key has the same semantics as the `--add-disk` argument
-to `qemuexec`. It is currently only supported on `qemu`.
+to `qemuexec`. It is currently only supported on `qemu`. The `primaryDisk` key
+also supports the same syntax and controls the primary boot disk.
 
 The `injectContainer` boolean if set will cause the framework to inject
 the ostree base image container into the target system; the path can be
diff --git a/mantle/kola/harness.go b/mantle/kola/harness.go
index 5d4671a60c..6ecd84b81d 100644
--- a/mantle/kola/harness.go
+++ b/mantle/kola/harness.go
@@ -1020,6 +1020,7 @@ type externalTestMeta struct {
 	Tags                      string   `json:"tags,omitempty"                      yaml:"tags,omitempty"`
 	RequiredTag               string   `json:"requiredTag,omitempty"               yaml:"requiredTag,omitempty"`
 	AdditionalDisks           []string `json:"additionalDisks,omitempty"           yaml:"additionalDisks,omitempty"`
+	PrimaryDisk               string   `json:"primaryDisk,omitempty"               yaml:"primaryDisk,omitempty"`
 	InjectContainer           bool     `json:"injectContainer,omitempty"           yaml:"injectContainer,omitempty"`
 	MinMemory                 int      `json:"minMemory,omitempty"                 yaml:"minMemory,omitempty"`
 	MinDiskSize               int      `json:"minDisk,omitempty"                   yaml:"minDisk,omitempty"`
@@ -1233,6 +1234,7 @@ ExecStart=%s
 		Tags:          []string{"external"},
 
 		AdditionalDisks:           targetMeta.AdditionalDisks,
+		PrimaryDisk:               targetMeta.PrimaryDisk,
 		InjectContainer:           targetMeta.InjectContainer,
 		MinMemory:                 targetMeta.MinMemory,
 		MinDiskSize:               targetMeta.MinDiskSize,
@@ -1752,6 +1754,7 @@ func runTest(h *harness.H, t *register.Test, pltfrm string, flight platform.Flig
 
 		options := platform.MachineOptions{
 			MultiPathDisk:             t.MultiPathDisk,
+			PrimaryDisk:               t.PrimaryDisk,
 			AdditionalDisks:           t.AdditionalDisks,
 			MinMemory:                 t.MinMemory,
 			MinDiskSize:               t.MinDiskSize,
diff --git a/mantle/kola/register/register.go b/mantle/kola/register/register.go
index 65bedb205c..a2ede2e674 100644
--- a/mantle/kola/register/register.go
+++ b/mantle/kola/register/register.go
@@ -70,7 +70,7 @@ type Test struct {
 	RequiredTag          string        // if specified, test is filtered by default unless tag is provided -- defaults to none
 	Description          string        // test description
 
-	// Whether the primary disk is multipathed.
+	// Whether the primary disk is multipathed. Deprecated in favour of PrimaryDisk.
 	MultiPathDisk bool
 
 	// Sizes of additional empty disks to attach to the node, followed by
@@ -78,13 +78,18 @@ type Test struct {
 	// "5G:mpath,foo,bar"]) -- defaults to none.
 	AdditionalDisks []string
 
+	// Size of primary disk to attach to the node, followed by
+	// comma-separated list of optional options (e.g. "20G:mpath"]).
+	PrimaryDisk string
+
 	// InjectContainer will cause the ostree base image to be injected into the target
 	InjectContainer bool
 
 	// Minimum amount of memory in MB required for test.
 	MinMemory int
 
-	// Minimum amount of primary disk in GB required for test.
+	// Minimum amount of primary disk in GB required for test. Deprecated in favour
+	// of PrimaryDisk.
 	MinDiskSize int
 
 	// Additional amount of NICs required for test.
diff --git a/mantle/platform/machine/qemu/cluster.go b/mantle/platform/machine/qemu/cluster.go
index ffbec20470..114daaf054 100644
--- a/mantle/platform/machine/qemu/cluster.go
+++ b/mantle/platform/machine/qemu/cluster.go
@@ -140,34 +140,33 @@ func (qc *Cluster) NewMachineWithQemuOptions(userdata *conf.UserData, options pl
 		builder.MemoryMiB = 4096 // SE needs at least 4GB
 	}
 
-	channel := "virtio"
+	var primaryDisk platform.Disk
+	if options.PrimaryDisk != "" {
+		var diskp *platform.Disk
+		if diskp, err = platform.ParseDisk(options.PrimaryDisk); err != nil {
+			return nil, errors.Wrapf(err, "parsing primary disk spec '%s'", options.PrimaryDisk)
+		}
+		primaryDisk = *diskp
+	}
+
 	if qc.flight.opts.Nvme || options.Nvme {
-		channel = "nvme"
+		primaryDisk.Channel = "nvme"
 	}
-	sectorSize := 0
-	logicalSectorSize := 0
 	if qc.flight.opts.Native4k {
-		sectorSize = 4096
+		primaryDisk.SectorSize = 4096
 	} else if qc.flight.opts.Disk512e {
-		sectorSize = 4096
-		logicalSectorSize = 512
+		primaryDisk.SectorSize = 4096
+		primaryDisk.LogicalSectorSize = 512
 	}
-	multiPathDisk := options.MultiPathDisk || qc.flight.opts.MultiPathDisk
-	var diskSize string
-	if options.MinDiskSize > 0 {
-		diskSize = fmt.Sprintf("%dG", options.MinDiskSize)
-	} else {
-		diskSize = qc.flight.opts.DiskSize
+	if options.MultiPathDisk || qc.flight.opts.MultiPathDisk {
+		primaryDisk.MultiPathDisk = true
 	}
-	primaryDisk := platform.Disk{
-		BackingFile:       qc.flight.opts.DiskImage,
-		Channel:           channel,
-		Size:              diskSize,
-		SectorSize:        sectorSize,
-		LogicalSectorSize: logicalSectorSize,
-		MultiPathDisk:     multiPathDisk,
+	if options.MinDiskSize > 0 {
+		primaryDisk.Size = fmt.Sprintf("%dG", options.MinDiskSize)
+	} else if qc.flight.opts.DiskSize != "" {
+		primaryDisk.Size = qc.flight.opts.DiskSize
 	}
-
+	primaryDisk.BackingFile = qc.flight.opts.DiskImage
 	if options.OverrideBackingFile != "" {
 		primaryDisk.BackingFile = options.OverrideBackingFile
 	}
diff --git a/mantle/platform/platform.go b/mantle/platform/platform.go
index ddcaf8ebb8..4ceb10a667 100644
--- a/mantle/platform/platform.go
+++ b/mantle/platform/platform.go
@@ -155,6 +155,7 @@ type Flight interface {
 
 type MachineOptions struct {
 	MultiPathDisk             bool
+	PrimaryDisk               string
 	AdditionalDisks           []string
 	MinMemory                 int
 	MinDiskSize               int