Check for EINTR from KVM_CREATE_VM

The kernel may return EINTR from:

kvm_create_vm
  kvm_init_mmu_notifier
    mmu_notifier_register
      do_mmu_notifier_register
        mm_take_all_locks

Go 1.14's preemptive scheduling signals make hitting this much more likely.

PiperOrigin-RevId: 291212669

pkg/sentry/platform/kvm/kvm.go

@@ -62,10 +62,20 @@ func New(deviceFile *os.File) (*KVM, error) {
 	}
 
 	// Create a new VM fd.
-	vm, _, errno := syscall.RawSyscall(syscall.SYS_IOCTL, fd, _KVM_CREATE_VM, 0)
+	var (
+		vm    uintptr
+		errno syscall.Errno
+	)
+	for {
+		vm, _, errno = syscall.Syscall(syscall.SYS_IOCTL, fd, _KVM_CREATE_VM, 0)
+		if errno == syscall.EINTR {
+			continue
+		}
 		if errno != 0 {
 			return nil, fmt.Errorf("creating VM: %v", errno)
 		}
+		break
+	}
 	// We are done with the device file.
 	deviceFile.Close()