vm: dedup VM count restriction in debug mode

Move the VM count restriction logic info vm package.
This avoids lots of duplication, makes it supported
for VM types that failed to do this, and allows
to unify more VM count logic in future.

1 files changed, 12 insertions, 4 deletions

diff --git a/vm/vm.go b/vm/vm.go
index 27e6f319e..91398167d 100644
--- a/vm/vm.go
+++ b/vm/vm.go
@@ -20,6 +20,7 @@ import (
 	"sync/atomic"
 	"time"
 
+	"github.com/google/syzkaller/pkg/log"
 	"github.com/google/syzkaller/pkg/mgrconfig"
 	"github.com/google/syzkaller/pkg/osutil"
 	"github.com/google/syzkaller/pkg/report"
@@ -48,6 +49,7 @@ type Pool struct {
 	workdir            string
 	template           string
 	timeouts           targets.Timeouts
+	count              int
 	activeCount        int32
 	snapshot           bool
 	hostFuzzer         bool
@@ -131,12 +133,18 @@ func Create(cfg *mgrconfig.Config, debug bool) (*Pool, error) {
 	if err != nil {
 		return nil, err
 	}
+	count := impl.Count()
+	if debug && count > 1 {
+		log.Logf(0, "limiting number of VMs from %v to 1 in debug mode", count)
+		count = 1
+	}
 	return &Pool{
 		impl:       impl,
 		typ:        typ,
 		workdir:    env.Workdir,
 		template:   cfg.WorkdirTemplate,
 		timeouts:   cfg.Timeouts,
+		count:      count,
 		snapshot:   cfg.Snapshot,
 		hostFuzzer: cfg.SysTarget.HostFuzzer,
 		statOutputReceived: stat.New("vm output", "Bytes of VM console output received",
@@ -145,12 +153,12 @@ func Create(cfg *mgrconfig.Config, debug bool) (*Pool, error) {
 }
 
 func (pool *Pool) Count() int {
-	return pool.impl.Count()
+	return pool.count
 }
 
 func (pool *Pool) Create(index int) (*Instance, error) {
-	if index < 0 || index >= pool.Count() {
-		return nil, fmt.Errorf("invalid VM index %v (count %v)", index, pool.Count())
+	if index < 0 || index >= pool.count {
+		return nil, fmt.Errorf("invalid VM index %v (count %v)", index, pool.count)
 	}
 	workdir, err := osutil.ProcessTempDir(pool.workdir)
 	if err != nil {
@@ -335,7 +343,7 @@ func (inst *Instance) Close() error {
 type Dispatcher = dispatcher.Pool[*Instance]
 
 func NewDispatcher(pool *Pool, def dispatcher.Runner[*Instance]) *Dispatcher {
-	return dispatcher.NewPool(pool.Count(), pool.Create, def)
+	return dispatcher.NewPool(pool.count, pool.Create, def)
 }
 
 type monitor struct {