On Wed, Jul 27, 2016 at 10:01:41AM +0530, Bharata B Rao wrote: > On Wed, Jul 27, 2016 at 08:22:51AM +0530, Bharata B Rao wrote: > > Hi, > > > > Coalesced mmio buffer is part of vCPU 0's kvm_run mmap'ed area > > and with the introduction of CPU hotplug, vCPU 0 can be removed on > > PowerPC leading to the below seen segfault in QEMU. > > > > > > This happens because during CPU removal, though we park the kvm_fd > > corresponding to the removed vCPU thread, we unmap the kvm_run (and > > hence coalesced mmio ring). > > > <snip> > > What would be the best way to fix this ? Is disassociating > > coalesced_mmio_ring > > from vCPU 0's kvm_run the correct solution ? > > May be PowerPC too should do what x86 does like below for now ?
I think that's what we need to do short term. In the 2.8 timeframe,
separating the mmio ring out from the vcpu state sounds like a good
idea, but I don't really know how complicated that will be.
>
> commit 73360e27850b213327011f7e22e03865b8c0dd5b
> Author: Igor Mammedov <imamm...@redhat.com>
> Date: Mon Jul 18 10:31:22 2016 +0200
>
> pc: Forbid BSP removal
>
> Boot CPU is assumed to always present in QEMU code, so
> untile that assumptions are gone, deny removal request,
> In another words QEMU won't support BSP hot-unplug.
>
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