temporary PR to help investigate ZONE_NORMAL

neonvm/README.md

@@ -115,7 +115,7 @@ To adjust the kernel config:
 
 ```
 cd hack/kernel
-docker build --build-arg KERNEL_VERSION=6.1.92 --platform linux/x86_64 --target build-deps -t kernel-build-deps -f Dockerfile.kernel-builder .
+docker build --build-arg KERNEL_VERSION=6.1.63 --platform linux/x86_64 --target build-deps -t kernel-build-deps -f Dockerfile.kernel-builder .
 docker run --rm -v $PWD:/host --name kernel-build -it kernel-build-deps bash
 # inside that bash shell, do the menuconfig, then copy-out the config to /host
 ```

neonvm/apis/neonvm/v1/virtualmachine_types.go

@@ -20,6 +20,7 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
+	"slices"
 
 	"github.com/samber/lo"
 
@@ -172,6 +173,8 @@ type Guest struct {
 	// +optional
 	MemorySlots MemorySlots `json:"memorySlots"`
 	// +optional
+	MemoryProvider *MemoryProvider `json:"memoryProvider,omitempty"`
+	// +optional
 	RootDisk RootDisk `json:"rootDisk"`
 	// Docker image Entrypoint array replacement.
 	// +optional
@@ -194,6 +197,24 @@ type Guest struct {
 	Settings *GuestSettings `json:"settings,omitempty"`
 }
 
+const virtioMemBlockSizeBytes = 8 * 1024 * 1024 // 8 MiB
+
+// ValidateForMemoryProvider returns an error iff the guest memory settings are invalid for the
+// MemoryProvider.
+//
+// This is used in two places. First, to validate VirtualMachine object creation. Second, to handle
+// the defaulting behavior for VirtualMachines that would be switching from DIMMSlots to VirtioMem
+// on restart. We place more restrictions on VirtioMem because we use 8MiB block sizes, so changing
+// to a new default can only happen if the memory slot size is a multiple of 8MiB.
+func (g Guest) ValidateForMemoryProvider(p MemoryProvider) error {
+	if p == MemoryProviderVirtioMem {
+		if g.MemorySlotSize.Value()%virtioMemBlockSizeBytes != 0 {
+			return fmt.Errorf("memorySlotSize invalid for memoryProvider VirtioMem: must be a multiple of 8Mi")
+		}
+	}
+	return nil
+}
+
 type GuestSettings struct {
 	// Individual lines to add to a sysctl.conf file. See sysctl.conf(5) for more
 	// +optional
@@ -361,6 +382,29 @@ type MemorySlots struct {
 	Use *int32 `json:"use,omitempty"`
 }
 
+// +kubebuilder:validation:Enum=DIMMSlots;VirtioMem
+type MemoryProvider string
+
+const (
+	MemoryProviderDIMMSlots MemoryProvider = "DIMMSlots"
+	MemoryProviderVirtioMem MemoryProvider = "VirtioMem"
+)
+
+// FlagFunc is a parsing function to be used with flag.Func
+func (p *MemoryProvider) FlagFunc(value string) error {
+	possibleValues := []string{
+		string(MemoryProviderDIMMSlots),
+		string(MemoryProviderVirtioMem),
+	}
+
+	if !slices.Contains(possibleValues, value) {
+		return fmt.Errorf("Unknown MemoryProvider %q, must be one of %v", value, possibleValues)
+	}
+
+	*p = MemoryProvider(value)
+	return nil
+}
+
 type RootDisk struct {
 	Image string `json:"image"`
 	// +optional
@@ -493,6 +537,8 @@ type VirtualMachineStatus struct {
 	// +optional
 	MemorySize *resource.Quantity `json:"memorySize,omitempty"`
 	// +optional
+	MemoryProvider *MemoryProvider `json:"memoryProvider,omitempty"`
+	// +optional
 	SSHSecretName string `json:"sshSecretName,omitempty"`
 }
 
@@ -558,6 +604,7 @@ func (vm *VirtualMachine) Cleanup() {
 	vm.Status.Node = ""
 	vm.Status.CPUs = nil
 	vm.Status.MemorySize = nil
+	vm.Status.MemoryProvider = nil
 }
 
 func (vm *VirtualMachine) HasRestarted() bool {

neonvm/apis/neonvm/v1/virtualmachine_webhook.go

@@ -92,6 +92,13 @@ func (r *VirtualMachine) ValidateCreate() error {
 		}
 	}
 
+	// validate .spec.guest.memorySlotSize w.r.t. .spec.guest.memoryProvider
+	if r.Spec.Guest.MemoryProvider != nil {
+		if err := r.Spec.Guest.ValidateForMemoryProvider(*r.Spec.Guest.MemoryProvider); err != nil {
+			return fmt.Errorf(".spec.guest: %w", err)
+		}
+	}
+
 	// validate .spec.guest.memorySlots.use and .spec.guest.memorySlots.max
 	if r.Spec.Guest.MemorySlots.Use != nil {
 		if r.Spec.Guest.MemorySlots.Max == nil {
@@ -160,6 +167,7 @@ func (r *VirtualMachine) ValidateUpdate(old runtime.Object) error {
 		{".spec.guest.cpus.max", func(v *VirtualMachine) any { return v.Spec.Guest.CPUs.Max }},
 		{".spec.guest.memorySlots.min", func(v *VirtualMachine) any { return v.Spec.Guest.MemorySlots.Min }},
 		{".spec.guest.memorySlots.max", func(v *VirtualMachine) any { return v.Spec.Guest.MemorySlots.Max }},
+		// nb: we don't check memoryProvider here, we have some specific logic for that.
 		{".spec.guest.ports", func(v *VirtualMachine) any { return v.Spec.Guest.Ports }},
 		{".spec.guest.rootDisk", func(v *VirtualMachine) any { return v.Spec.Guest.RootDisk }},
 		{".spec.guest.command", func(v *VirtualMachine) any { return v.Spec.Guest.Command }},
@@ -187,6 +195,19 @@ func (r *VirtualMachine) ValidateUpdate(old runtime.Object) error {
 		}
 	}
 
+	// Only allow changing .spec.guest.memoryProvider if it was previously nil, and the new version
+	// is equal to .status.memoryProvider.
+	if !reflect.DeepEqual(before.Spec.Guest.MemoryProvider, r.Spec.Guest.MemoryProvider) {
+		if before.Spec.Guest.MemoryProvider != nil {
+			return errors.New(".spec.guest.memoryProvider cannot be changed once it is non-nil")
+		}
+		if !reflect.DeepEqual(r.Spec.Guest.MemoryProvider, r.Status.MemoryProvider) {
+			return errors.New(".spec.guest.memoryProvider cannot be set to any value other than .status.memoryProvider")
+		}
+	}
+
+	// {".spec.guest.memoryProvider", func(v *VirtualMachine) any { return v.Spec.Guest.MemoryProvider }},
+
 	// validate swap changes by comparing the SwapInfo for each.
 	//
 	// If there's an error with the old object, but NOT an error with the new one, we'll allow the

neonvm/config/controller/deployment.yaml

@@ -59,6 +59,7 @@ spec:
         # * cache.direct=on    - use O_DIRECT (don't abuse host's page cache!)
         # * cache.no-flush=on  - ignores disk flush operations (not needed; our disks are ephemeral)
         - "--qemu-disk-cache-settings=cache.writeback=on,cache.direct=on,cache.no-flush=on"
+        - "--default-memory-provider=DIMMSlots"
         - "--failure-pending-period=1m"
         - "--failing-refresh-interval=15s"
         env:

neonvm/config/crd/bases/vm.neon.tech_virtualmachines.yaml

@@ -2412,6 +2412,11 @@ spec:
                     type: array
                   kernelImage:
                     type: string
+                  memoryProvider:
+                    enum:
+                    - DIMMSlots
+                    - VirtioMem
+                    type: string
                   memorySlotSize:
                     anyOf:
                     - type: integer
@@ -2764,6 +2769,11 @@ spec:
                 type: string
               extraNetMask:
                 type: string
+              memoryProvider:
+                enum:
+                - DIMMSlots
+                - VirtioMem
+                type: string
               memorySize:
                 anyOf:
                 - type: integer

neonvm/controllers/config.go

@@ -1,6 +1,10 @@
 package controllers
 
-import "time"
+import (
+	"time"
+
+	vmv1 "github.com/neondatabase/autoscaling/neonvm/apis/neonvm/v1"
+)
 
 // ReconcilerConfig stores shared configuration for VirtualMachineReconciler and
 // VirtualMachineMigrationReconciler.
@@ -25,6 +29,10 @@ type ReconcilerConfig struct {
 	// used in setting up the VM disks via QEMU's `-drive` flag.
 	QEMUDiskCacheSettings string
 
+	// DefaultMemoryProvider is the memory provider (dimm slots or virtio-mem) that will be used for
+	// new VMs (or, when old ones restart) if nothing is explicitly set.
+	DefaultMemoryProvider vmv1.MemoryProvider
+
 	// FailurePendingPeriod is the period for the propagation of
 	// reconciliation failures to the observability instruments
 	FailurePendingPeriod time.Duration