Xen devel - Sep 2009 - Question about direct memory access of domU from dom0

Hello,

I am porting a C application that requires taking a snapshot of memory on
the computer you are running.  The original program uses an external PCI
card to read the memory and now I am trying to port this to xen.  I want to
run the program in the dom0 guest but the memory that it will be taking a
snapshot of is the of memory in the domU guest.  I am using the xen
hypervisor 3.3.  Is there any specific library or API I can use in C to do
this?  The xen api on xensource seems to only talk about xensource never
about the hypervisor alone.  Thank you.

Jeff


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On Thursday, 10 September 2009 at 16:55, Jeff Bickford
wrote:
> Hello,
> 
> I am porting a C application that requires taking a snapshot of memory on
the
> computer you are running.  The original program uses an external PCI card
to
> read the memory and now I am trying to port this to xen.  I want to run the
> program in the dom0 guest but the memory that it will be taking a snapshot
of
> is the of memory in the domU guest.  I am using the xen hypervisor 3.3.  Is
> there any specific library or API I can use in C to do this?  The xen api
on
> xensource seems to only talk about xensource never about the hypervisor
alone.
> Thank you.
Have a look at tools/libxc/xc_domain_save.c. That''s the heart of xm
save/xm migrate. Basically it''s:

1. pause the domU
2. map its memory
3. copy it out
4. unpause

You may need to map in batches if the guest memory is too large to fit
in your copying process''s address space.

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The shell command ''xm save <domain>'' will save the
memory image of a domain,
and more besides. If you''re interested in snapshotting just a
domain''s
memory, while the domain continues to run, then some variant of
tools/libxc/xc_domain_save.c:xc_domain_save() is what you want.

 -- Keir

On 10/09/2009 21:55, "Jeff Bickford" <tassadar27@gmail.com>
wrote:
> Hello,
> 
> I am porting a C application that requires taking a snapshot of memory on
the
> computer you are running.  The original program uses an external PCI card
to
> read the memory and now I am trying to port this to xen.  I want to run the
> program in the dom0 guest but the memory that it will be taking a snapshot
of
> is the of memory in the domU guest.  I am using the xen hypervisor 3.3.  Is
> there any specific library or API I can use in C to do this?  The xen api
on
> xensource seems to only talk about xensource never about the hypervisor
> alone.  Thank you.
> 
> Jeff
> 


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