Re: [Qemu-devel] [PATCH 03/11] pc: check if KVM has enough memory slots for DIMM devices

[Igor Mammedov <imammedo@redhat.com>]

On Tue, 04 Nov 2014 16:42:23 +0100
Paolo Bonzini <pbonzini@redhat.com> wrote:

> 
> 
> On 04/11/2014 16:39, Igor Mammedov wrote:
> >> > But he cannot even with your patch, if he was off by just a couple
> >> > items.  So I don't think the improvement is worth the extra complication
> >> > of the code and the small layering violation.
> > With this patch user can launch QEMU with exact max amount of possible
> > slots with exception that he won't hotplug other than pc-dimm devices
> > that consume KVM's memory slots (not sure if such exists (hotpluggable)).
> > but, sure we can drop this patch until someone complains.
> 
> Note that option ROM BARs (which are usually mapped only by firmware,
> but also when accessed via sysfs) and device assignment both consume
> memory slots.  Slots occupied by pflash can also come and go, depending
> on whether the flash is visible as ROM or in programming mode.
Then there is a bigger problem, once KVM slots are saturated QEMU will crash
if one of above actions from guest happens, and we can't even error out on them.

> 
> Paolo
>