migration/dirtyrate: Fix segmentation fault

Since the kvm_dirty_ring_enabled function accesses a null kvm_state
pointer when the KVM acceleration parameter is not specified, running
calc_dirty_rate with the -r or -b option causes a segmentation fault.

Signed-off-by: Masato Imai <mii@sfc.wide.ad.jp>
Message-ID: <20240507025010.1968881-1-mii@sfc.wide.ad.jp>
[Assert kvm_state when kvm_dirty_ring_enabled was called to fix it. - Hyman]
Signed-off-by: Hyman Huang <yong.huang@smartx.com>
1 file changed