Re: [Xen-devel] Re: How to get guest PTEs info of a HVM with EPT

[Tim Deegan <Tim.Deegan@xxxxxxxxxx>]

At 23:30 +0000 on 08 Feb (1297207857), KennyChen wrote:
> Thanks for the hint, Tim, but I still got some questions.
> 
> When I put debug dump in the guest_walk_tables() to observe the l4e entry
> (64-bit guest with 4GB ram, Centos 5.5), is it normal to get a l4e 
> "10e21a067".

Yes, quite normal.

> It seems the gfn 0x10e21a has exceeded the maximum physical memory of the 
> guest
> (0x100000 for 4GB). Is this a bug of the guest or some tricks in the l4e?

Neither.  Some addresses below 4GB don't contain RAM, so the highest RAM
address is larger than the amount of RAM.

> The other weird thing is gfn_to_mfn_unshare() called inside
> hap_gva_to_gfn().  Why is it necessary to unshare the page when we
> traverse the page table? we are just reading it right?

You're right, it's probably not necessary, though pagetable pages are
unlikely to be shared between domains.  I'm not inclined to change it
just now since we're supposed to be freezing for the 4.1 release.

Tim.

-- 
Tim Deegan <Tim.Deegan@xxxxxxxxxx>
Principal Software Engineer, Xen Platform Team
Citrix Systems UK Ltd.  (Company #02937203, SL9 0BG)

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel