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

To: "Charles Coffing" <ccoffing@xxxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH] Fix auto-ballooning of dom0 for HVM domains
From: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Date: Mon, 22 May 2006 16:03:40 +0100
Cc: Kevin Tian <kevin.tian@xxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx, Yunhong Jiang <yunhong.jiang@xxxxxxxxx>, xen-ia64-devel@xxxxxxxxxxxxxxxxxxx
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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?

 -- Keir

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