rhcos: ami regions from rhcos stream at runtime

Currently, the installer relies on a generated go file for determining
the AWS region in which the RHCOS image is published. The `go generate`
directive was inadvertently removed in openshift#4582.
Rather than resurrecting the directive, this commit removes the generated
code in favor of gathering the regions directly from the rhcos stream
data when needed.

https://issues.redhat.com/browse/CORS-1838

hack/verify-codegen.sh

@@ -3,8 +3,6 @@
 if [ "$IS_CONTAINER" != "" ]; then
   set -xe
   go generate ./pkg/types/installconfig.go
-  # See https://github.com/openshift/installer/pull/5447#discussion_r762340594
-  # go generate ./pkg/rhcos/ami.go
   set +ex
   git diff --exit-code
 else

pkg/asset/installconfig/aws/regions.go

@@ -2,7 +2,6 @@ package aws
 
 import (
 	"github.com/aws/aws-sdk-go/aws/endpoints"
-	"k8s.io/apimachinery/pkg/util/sets"
 
 	"github.com/openshift/installer/pkg/rhcos"
 	"github.com/openshift/installer/pkg/types"
@@ -12,10 +11,7 @@ import (
 // This is subset of AWS regions and the regions where RHEL CoreOS images are published.
 // The result is a map of region identifier to region description
 func knownRegions(architecture types.Architecture) map[string]string {
-	required := sets.NewString(rhcos.AMIRegionsX86_64...)
-	if architecture == types.ArchitectureARM64 {
-		required = sets.NewString(rhcos.AMIRegionsAARCH64...)
-	}
+	required := rhcos.AMIRegions(architecture)
 
 	regions := make(map[string]string)
 	for _, partition := range endpoints.DefaultPartitions() {

pkg/asset/installconfig/aws/validation.go

@@ -20,7 +20,6 @@ import (
 	"github.com/openshift/installer/pkg/rhcos"
 	"github.com/openshift/installer/pkg/types"
 	awstypes "github.com/openshift/installer/pkg/types/aws"
-	awsvalidation "github.com/openshift/installer/pkg/types/aws/validation"
 )
 
 type resourceRequirements struct {
@@ -81,17 +80,8 @@ func validatePlatform(ctx context.Context, meta *Metadata, fldPath *field.Path,
 
 func validateAMI(ctx context.Context, config *types.InstallConfig) field.ErrorList {
 	// accept AMI from the rhcos stream metadata
-	switch config.ControlPlane.Architecture {
-	case types.ArchitectureAMD64:
-		if sets.NewString(rhcos.AMIRegionsX86_64...).Has(config.Platform.AWS.Region) {
-			return nil
-		}
-	case types.ArchitectureARM64:
-		if sets.NewString(rhcos.AMIRegionsAARCH64...).Has(config.Platform.AWS.Region) {
-			return nil
-		}
-	default:
-		return field.ErrorList{field.NotSupported(field.NewPath("controlPlane", "architecture"), config.ControlPlane.Architecture, awsvalidation.ValidArchitectureValues)}
+	if rhcos.AMIRegions(config.ControlPlane.Architecture).Has(config.Platform.AWS.Region) {
+		return nil
 	}
 
 	// accept AMI specified at the platform level

pkg/rhcos/ami_regions.go

@@ -0,0 +1,33 @@
+package rhcos
+
+import (
+	"context"
+
+	"github.com/coreos/stream-metadata-go/arch"
+	"github.com/sirupsen/logrus"
+	"k8s.io/apimachinery/pkg/util/sets"
+
+	"github.com/openshift/installer/pkg/types"
+)
+
+// AMIRegions returns the AWS regions in which an RHCOS AMI for the specified architecture is published.
+func AMIRegions(architecture types.Architecture) sets.String {
+	stream, err := FetchCoreOSBuild(context.Background())
+	if err != nil {
+		logrus.Error("could not fetch the rhcos stream data: %w", err)
+		return nil
+	}
+	rpmArch := arch.RpmArch(string(architecture))
+	awsImages := stream.Architectures[rpmArch].Images.Aws
+	if awsImages == nil {
+		return nil
+	}
+	regions := make([]string, 0, len(awsImages.Regions))
+	for name, r := range awsImages.Regions {
+		if r.Image == "" {
+			continue
+		}
+		regions = append(regions, name)
+	}
+	return sets.NewString(regions...)
+}