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Re: [Xen-devel] Identifying pagetype in they hypervisor

To: "Mark Williamson" <mark.williamson@xxxxxxxxxxxx>
Subject: Re: [Xen-devel] Identifying pagetype in they hypervisor
From: "Mike Sun" <msun@xxxxxxxxxx>
Date: Sun, 24 Aug 2008 22:01:05 -0400
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
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Thanks Mark.  That's what I think I'm looking for.

I think I've managed to confuse myself a bit again (haven't touched
the modifications I made to the shadow code in a while) with the
gmfn/mfn naming in the shadow code.  In _sh_propagate(...,
target_fmn,..) and _sh_mark_dirty(..., gmfn), I'm assuming that a real
machine frame number is passed to those functions, not a
pseudo-physical one... am I correct?

Basically, I need to be sure that when the sh_page_fault_handler()
eventually calls _sh_propagate(), it passes the machine frame number
of the faulting page, not the HVM guest's perceived physical address


On Sun, Aug 24, 2008 at 9:10 PM, Mark Williamson
<mark.williamson@xxxxxxxxxxxx> wrote:
> I'm looking at the latest code but I would think the same code applies.
> Maybe you could try mfn_to_page() to get the struct page_info * and then poke
> about in that for the current type?  In order to make this useful you'd
> probably have to do a get_page or similar to avoid races with other CPUs.
> Cheers,
> Mark
> On Monday 25 August 2008 01:47:19 Mike Sun wrote:
>> Hi --
>> I'm working off of a bit older branch, 3.1.0, but hopefully the
>> question is still relevant.
>> In the suspend/restore code in 'tools/libxc/xc_domain_save.c', as part
>> of the saved record, a list of pfn_types are saved prior to the actual
>> pages themselves.  These pfn_types are pfns with a type bits
>> associated with them that are accessed with the XEN_DOMCTL_PFINFO_XTAB
>> bitmask.
>> I'm doing some copy-on-write work, and when I intercept writes in the
>> hypervisor, I need to copy both the actual page, and the type
>> associated with the page (so that it could later be properly written
>> out to the save record).  I've modified the shadow page table code to
>> handle write faults associated with CoW and am able to get the mfn of
>> the faulting page and perform the copy; I cannot seem to find where
>> given the mfn, I can find the page type associated with it.  Could
>> anybody help point me to the right place or direction?
>> Much thanks,
>> Mike
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