qemu: arm64: Set defaultGICVersion to 3 to limit the max vCPU number

After removing dectect of host gic version, we need to limit the max vCPU
in different cases.

Given that in most cases, Kata is running on gicv3 host, set it as default
value. If the user really want to run Kata on gicv2 host, he/she need to
set default_maxvcpus in toml file to 8 instead of 0.

In summary, If the user uses host gicv3 gicv4, everything is fine
            If the user uses host gicv2, set default_maxvcpus=8

Fixes: #2614
Signed-off-by: Jia He <[email protected]>

cli/config/configuration-fc.toml.in

@@ -55,6 +55,7 @@ default_vcpus = 1
 # `default_maxvcpus = 8` the memory footprint will be small, but 8 will be the maximum number of
 # vCPUs supported by the SB/VM. In general, we recommend that you do not edit this variable,
 # unless you know what are you doing.
+# NOTICE: on arm platform with gicv2 interrupt controller, set it to 8.
 default_maxvcpus = @DEFMAXVCPUS@
 
 # Bridges can be used to hot plug devices.

cli/config/configuration-qemu-virtiofs.toml.in

@@ -58,6 +58,7 @@ default_vcpus = 1
 # `default_maxvcpus = 8` the memory footprint will be small, but 8 will be the maximum number of
 # vCPUs supported by the SB/VM. In general, we recommend that you do not edit this variable,
 # unless you know what are you doing.
+# NOTICE: on arm platform with gicv2 interrupt controller, set it to 8.
 default_maxvcpus = @DEFMAXVCPUS@
 
 # Bridges can be used to hot plug devices.

cli/config/configuration-qemu.toml.in

@@ -59,6 +59,7 @@ default_vcpus = 1
 # `default_maxvcpus = 8` the memory footprint will be small, but 8 will be the maximum number of
 # vCPUs supported by the SB/VM. In general, we recommend that you do not edit this variable,
 # unless you know what are you doing.
+# NOTICE: on arm platform with gicv2 interrupt controller, set it to 8.
 default_maxvcpus = @DEFMAXVCPUS@
 
 # Bridges can be used to hot plug devices.

virtcontainers/qemu_arm64.go

@@ -7,7 +7,6 @@ package virtcontainers
 
 import (
 	"context"
-	"runtime"
 	"time"
 
 	govmmQemu "github.com/intel/govmm/qemu"
@@ -26,6 +25,8 @@ const qmpMigrationWaitTimeout = 10 * time.Second
 
 const defaultQemuMachineOptions = "usb=off,accel=kvm,gic-version=host"
 
+var defaultGICVersion = uint32(3)
+
 var qemuPaths = map[string]string{
 	QemuVirt: defaultQemuPath,
 }
@@ -56,7 +57,7 @@ var gicList = map[uint32]uint32{
 
 // MaxQemuVCPUs returns the maximum number of vCPUs supported
 func MaxQemuVCPUs() uint32 {
-	return uint32(runtime.NumCPU())
+	return gicList[defaultGICVersion]
 }
 
 func newQemuArch(config HypervisorConfig) qemuArch {

virtcontainers/qemu_arm64_test.go

@@ -9,8 +9,6 @@ import (
 	"fmt"
 	"io/ioutil"
 	"os"
-	"path/filepath"
-	"runtime"
 	"testing"
 
 	govmmQemu "github.com/intel/govmm/qemu"
@@ -57,50 +55,8 @@ func TestQemuArm64MemoryTopology(t *testing.T) {
 func TestMaxQemuVCPUs(t *testing.T) {
 	assert := assert.New(t)
 
-	type testData struct {
-		contents       string
-		expectedResult uint32
-	}
-
-	data := []testData{
-		{"", uint32(runtime.NumCPU())},
-		{"  1:          0          0     GICv2  25 Level     vgic \n", uint32(8)},
-		{"  1:          0          0     GICv3  25 Level     vgic \n", uint32(123)},
-		{"  1:          0          0     GICv4  25 Level     vgic \n", uint32(123)},
-	}
-
-	tmpdir, err := ioutil.TempDir("", "")
-	if err != nil {
-		panic(err)
-	}
-	defer os.RemoveAll(tmpdir)
-
-	savedGicProfile := gicProfile
-
-	testGicProfile := filepath.Join(tmpdir, "interrupts")
-
-	// override
-	gicProfile = testGicProfile
-
-	defer func() {
-		gicProfile = savedGicProfile
-	}()
-
-	savedHostGICVersion := hostGICVersion
-
-	defer func() {
-		hostGICVersion = savedHostGICVersion
-	}()
-
-	for _, d := range data {
-		err := ioutil.WriteFile(gicProfile, []byte(d.contents), os.FileMode(0640))
-		assert.NoError(err)
-
-		hostGICVersion = getHostGICVersion()
-		vCPUs := MaxQemuVCPUs()
-
-		assert.Equal(d.expectedResult, vCPUs)
-	}
+	vCPUs := MaxQemuVCPUs()
+	assert.Equal(uint32(123), vCPUs)
 }
 
 func TestQemuArm64AppendBridges(t *testing.T) {