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Re: [Xen-devel] [PATCH][VT] Patch to allow VMX domainsto be destroyedor

To: "Jiang, Yunhong" <yunhong.jiang@xxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH][VT] Patch to allow VMX domainsto be destroyedor shut down cleanly
From: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Date: Mon, 19 Sep 2005 13:40:50 +0100
Cc: Khoa Huynh <khoa@xxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx, xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
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On 19 Sep 2005, at 11:52, Jiang, Yunhong wrote:

I think it's more correct to do get/put in vmx_set_cr0 (at that point
we can know what format the pagetables should be, for example
(32/32p/64). But I think it's a bigger cleanup patch.

Do you mean put all get/put on vmx_set_cr0 ? even for paging enabled case?

No, I mean that get/put on cr3 change (or guest destruction) should be gated on CR0_PG. Then, additionally, get or put is required when CR0_PG is toggled.

And there is one more issue .If the guest is destroyed before the kernel enabling paging, how about the page pointed by cr3? It may cause one referece count left. The reason is, currently when destroy domain, only domain->guest_table is released. However, if the paging is not enabled, then the get_page on vmx_set_cr0 has no corresponding put_page, which may cause problem. Hope comments on this point.

Doing what I describe above would fix this: CR0_PG would be clear, so put_page() would not happen.


Whatever you go for: please send a complete tested patch. :-)

Sure!

Thanks!

 -- Keir


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