Re: [PATCH] Fix auto-ballooning of dom0 for HVM domains

["Charles Coffing" <ccoffing@novell.com>]

>>> On Mon, May 22, 2006 at  9:03 AM, in message
<6085df031157d9ce198b72191501db21@cl.cam.ac.uk>, Keir Fraser
<Keir.Fraser@cl.cam.ac.uk> wrote: 

> On 22 May 2006, at 15:51, Charles Coffing wrote:
> 
>> HVM domains need some extra memory free for the shadow page tables,
>> otherwise they may crash the entire machine while they are running,
or
>> the HVM domain itself may crash (exact behavior depends on whether
you
>> have Yunhong's patch to change BUGs to domain_crash).
>>
>> This slack space is calculated into the memory size for HVM
domains,
>> but what happens if you then start a PV domain afterwards?  Only
the
>> minimally required memory is freed up, then the PV domain takes it
all,
>> leaving the HVM domain with no slack == crash.
> 
> Where does the slack from the previous HVM guest startup go? Are you

> saying that dom0 only frees up PV- guest- size minus existing-
slack?

Correct.

Unless, of course, the HVM domain has eaten up some of the slack in the
mean-time, in which case dom0 frees up PV-guest-size minus
remaining-slack.