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Re: [Xen-devel] Hypercall from HVM guest

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Subject: Re: [Xen-devel] Hypercall from HVM guest
From: "Emre Can Sezer" <ecsezer@xxxxxxxx>
Date: Thu, 25 Sep 2008 10:58:50 -0400 (EDT)
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> Hi,
> I'm trying to communicate some information from an HVM guest to Xen.
> Passing a pointer to a buffer would suffice and the communication will be
> single sided.  What is the best way to do this?
> I've looked into making a hypercall from an HVM guest and came across this
> post on this mailing list by Steve Ofsthun:
> http://lists.xensource.com/archives/html/xen-devel/2006-04/msg00526.html
> However, I'm unable to get this code to work.  I'm running a 64-bit system
> with the linux-2.6.26 kernel downloaded from kernel.org on top of
> xen-3.2.2.  When I compile, I get compilation errors resulting from
> hypercall.h.  I believe this code is intended for 32 bit guests only as
> the structure definitions are different fot the pte_t type.
> The error was:
> In file included from include/asm/xen/hypervisor.h:53,
>                  from /home/ecsezer/kernels/vmcall/./features.c:11:
> include/asm/xen/hypercall.h: In function 'HYPERVISOR_update_va_mapping':
> include/asm/xen/hypercall.h:230: error: 'pte_t' has no member named
> 'pte_low'
> I tried to modify this code to get rid of compilation errors but a final
> warning still persists and loading the module causes a seg fault.  The
> warning I get is:
>   CC [M]  /home/ecsezer/kernels/hyper/./hypercall.o
> {standard input}: Assembler messages:
> {standard input}:149: Warning: indirect call without `*'
> So I tried to compile with mercurial repository version linux-2.6.18-xen
> and that compiles fine.  However, due to being a different version, I
> can't use the resulting module.
> I would appreciate any insight as to how to proceed.  What could be the
> problem?  Perhaps there is an easier way of passing the information I want
> without a full blown hypercall interface?
> Thanks,
> John
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As a side note, when I compile and load the module, I get a seg fault but
the module appears when I lsmod.  When I try to remove I get the error:
ERROR: Module test is in use



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