qemu: refactor maximum vcpus supported in aarch64

on aarch64, we support different gic interrupt controllers.
The maximum number of vCPUs depends on the GIC version, or on how
many redistributors we can fit into the memory map.

Fixes: kata-containers#584

Signed-off-by: Penny Zheng <[email protected]>
igned-off-by: Wei Chen <[email protected]>

virtcontainers/qemu_arm64.go

@@ -6,9 +6,12 @@
 package virtcontainers
 
 import (
+	"io/ioutil"
+	"regexp"
 	"runtime"
 
 	govmmQemu "github.com/intel/govmm/qemu"
+	"github.com/sirupsen/logrus"
 )
 
 type qemuArm64 struct {
@@ -38,15 +41,41 @@ var kernelRootParams = []Param{
 	{"root", "/dev/vda1"},
 }
 
+// variables rather than consts to allow tests to modify them
+var interruptFile = "/proc/interrupts"
+//on aarch64, we support different gic interrupt controllers
+//maximum number of vCPUs depends on the GIC version, or on how
+//many redistributors we can fit into the memory map.
+var gicList = map[string]uint32{
+	"GICv2": uint32(8),
+	"GICv3": uint32(123),
+	"GICv4": uint32(123),
+}
+
 var supportedQemuMachines = []govmmQemu.Machine{
 	{
 		Type:    QemuVirt,
 		Options: defaultQemuMachineOptions,
 	},
 }
 
+// Logger returns a logrus logger appropriate for logging qemu-aarch64 messages
+func qemuArmLogger() *logrus.Entry {
+	return virtLog.WithField("subsystem", "qemu-aarch64")
+}
+
 // MaxQemuVCPUs returns the maximum number of vCPUs supported
 func MaxQemuVCPUs() uint32 {
+	bytes, err := ioutil.ReadFile(interruptFile)
+	if err != nil {
+		qemuArmLogger().WithError(err).Error("Failed to read /proc/interrrupts")
+	}
+	for gicType, vCPUs := range gicList {
+		pattern := regexp.MustCompile(`\b` + gicType + `\b`)
+		if pattern.MatchString(string(bytes)) {
+			return vCPUs
+		}
+	}
 	return uint32(runtime.NumCPU())
 }