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[Xen-devel] RE: Doubt regarding virtual memory mapping from hypervisor t

To: Kaustubh Kabra <kaustubhwise@xxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx
Subject: [Xen-devel] RE: Doubt regarding virtual memory mapping from hypervisor to a domain
From: Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>
Date: Mon, 31 Jan 2011 07:36:40 -0800 (PST)
Cc: vasani.ashwin@xxxxxxxxx, keir@xxxxxxx, Tim.Deegan@xxxxxxxxxx
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> From: Kaustubh Kabra [mailto:kaustubhwise@xxxxxxxxx]
> I have allocated few order=9 pages in Xen memory space using
> alloc_domheap_pages(NULL,9,0) during boot time just before domain is
> created (dom0 = domain_create(0, DOMCRF_s3_integrity, DOM0_SSIDREF) in
> xen/arch/x86/setup.c).
> I got the following virtual addresses in xen log message-
> (XEN) a2k2: Virt_addr:ffff83011cc00000   MFN:11cc00
> (XEN) a2k2: Virt_addr:ffff83011ca00000   MFN:11ca00
> (XEN) a2k2: Virt_addr:ffff83011c800000   MFN:11c800
> (XEN) a2k2: Virt_addr:ffff83011c600000   MFN:11c600
> (XEN) a2k2: Virt_addr:ffff83011c400000   MFN:11c400
> (XEN) a2k2: Virt_addr:ffff83011c200000   MFN:11c200
> (XEN) a2k2: Virt_addr:ffff83011c000000   MFN:11c000
> (XEN) a2k2: Virt_addr:ffff83011be00000   MFN:11be00
> As per config.h file Xen memory map,the virtual mapping shows that the
> memory is  allocated in
> 1:1 direct mapping of all physical memory .Can anyone elaborate
> regarding this mapping ?

It's not clear what you are asking.  Can you be more precise?
> Now can I allocate this mapped memory reserved by Xen hypervisor to
> any domain through any existing or my new hypercall?

Again, it's not clear what you are asking.  If you are
asking if the guest can map the order=9 page into its
memory space, I think the answer is no.  If you are
asking if Xen can use the memory on behalf of a
domain, for example to copy data from the domain into
Xen (like tmem does), I think the answer is yes.

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