On Tue, Aug 05, 2014 at 06:28:54PM +0800, Amos Kong wrote: > 3.16 (guest hangs with two rng devices) > 3.16 + quick fix (can startup with two rng devices) (hotplug issue 1 + hotplug issue 2 exist) > lates torvalds/linux.git + amit 4 patches (can startup with two rng devices) (only hotplug issue 2 exists) > > However, the 4 patches also fixed the hang issue, the hotplug issue was fixed a little. > The hotplug issue is effected by the backend, or maybe it's not a real issue, because > the rng device can be hot-removed after dd process is killed. > > > Hotplug issue 1: > 1. boot up guest with two rng device (rng0 uses /dev/urandom, rng1 uses /dev/random) > 2. read data by dd in guest > 3 (option 1). hot-remove rng0, then hot-remove rng1 -> result: _only rng1_ can't be removed until dd process is killed > 3 (option 2). hot-remove rng1, then hot-remove rng0 -> result: two devices can be removed successfully, dd process will exit automatically. > > If we use /dev/urandom for rng0 and rng1, _rng0 & rng1_ can be removed, dd process will exit automatically. > > Hotplug issue 2: > If we use /dev/random for rng0 and rng1, _rng0 & rng1_ can't be removed until dd process is killed. > > Hotplug issue 3: > If we use /dev/random for rng0 and rng1, _only rng1_ can't be removed until dd process is killed. Hi Amit, I finally found the root problem and posted a fix to upstream: http://lists.linuxfoundation.org/pipermail/virtualization/2014-August/027049.html It can help to fix the hotplug issues on 3.16 & latest kernel, so stable kernel is CCed. > (The difference between /dev/random and /dev/urandom is the speed.) > > Thanks, Amos -- Amos. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
