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xen-users
[Xen-users] Re: [Xen-devel] Xen - Guest memory allocation
Thank you Derek,
I'm currently work on your idea and its cuming out as expected.
Let me confirm,
The domain builder inside dom0 calls populate_physmap(),
allocates pages for domUs,
and computes the following START_INFO_PAGE attributes
pt_base, mfn_list and nr_pt_frames.
But the source says, all the above attributes are VIRTUAL ADDRESSES
and on the contrary the book, 'The defenitive guide for XEN hypervisor' says
they are pseudo-physical addresses.
I know these two are different. But I'm still not clear,
Could you help me better understand the difference?
Dinesh C
> Date: Mon, 16 Jun 2008 23:09:31 +0100
> From: Derek.Murray@xxxxxxxxxxxx
> To: dinesh_chan8@xxxxxxxxxxx
> Subject: Re: [Xen-users] Re: [Xen-devel] Xen - Guest memory allocation
> CC: xen-devel@xxxxxxxxxxxxxxxxxxx; xen-users@xxxxxxxxxxxxxxxxxxx
>
> Hi Dinesh,
>
> The pages that are used for a DomU's memory are allocated when the
> domain builder (in Dom0) calls xc_domain_populate_physmap(), which
> executes a hypercall and ultimately calls populate_physmap() in
> xen/common/memory.c.
>
> I'm not terribly familiar with this code, but it looks like it might
> be possible to hack in a replacement to achieve your desired effect.
>
> Regards,
>
> Derek Murray.
>
> On Mon, Jun 16, 2008 at 10:52 PM, dinesh chandrasekaran
> <dinesh_chan8@xxxxxxxxxxx> wrote:
> >
> >>> by default, dom0 gets all the available memory (usable physical memory-
> >>> xen hypervisor). Then, when domU starts up, xen will decrease
> >>> dom0'sallocation >> via ballooning and allocate them to domU.
> >
> > Yes weiming you are correct. But ballooning could be disabled.
> >
> >>>Do you want to specify the exact physical memory address space used by
> >>> domU?
> >
> > Yes absolutly. Could that be done? (Hope by physical address you mean the
> > real/machine/RAM address)
> > If so should I have to edit xen source or Dom0 source.
> >
> > Thanks,
> > Dinesh C
> >
> >
> > ________________________________
> > Date: Mon, 16 Jun 2008 15:39:13 -0400
> > From: zephyr.zhao@xxxxxxxxx
> > To: dinesh_chan8@xxxxxxxxxxx
> > Subject: Re: [Xen-users] Re: [Xen-devel] Xen - Guest memory allocation
> > CC: xen-devel@xxxxxxxxxxxxxxxxxxx; xen-users@xxxxxxxxxxxxxxxxxxx
> >
> > by default, dom0 gets all the available memory (usable physical memory - xen
> > hypervisor). Then, when domU starts up, xen will decrease dom0's allocation
> > via ballooning and allocate them to domU.
> >
> > Do you want to specify the exact physical memory address space used by domU?
> >
> > On Mon, Jun 16, 2008 at 2:37 PM, dinesh chandrasekaran
> > <dinesh_chan8@xxxxxxxxxxx> wrote:
> >
> > Yes, ofcourse dom0 can see this range.
> >
> > But all the domUs memory has to fall in this restricted memory range (as
> > specified by mypci_usabe)?
> >
> > for example,
> > If I start three virtual machines, say VM1, VM2, VM3 with 64MB memory each,
> > how could I make sure that, the total 192MB for three VMs lie somewhere in
> > mypci_usable range only and not anywhere else.
> >
> > Thanks,
> > Dinesh C
> >
> > ________________________________
> > Date: Thu, 12 Jun 2008 22:37:17 -0400
> > From: zephyr.zhao@xxxxxxxxx
> > To: dinesh_chan8@xxxxxxxxxxx
> > Subject: Re: [Xen-users] Re: [Xen-devel] Xen - Guest memory allocation
> > CC: xen-devel@xxxxxxxxxxxxxxxxxxx; xen-users@xxxxxxxxxxxxxxxxxxx
> >
> > Can dom0 address the whole memory space if no other domU running? If so, it
> > can freely allocate memory to other guests.
> >
> > On Thu, Jun 12, 2008 at 3:34 PM, dinesh chandrasekaran
> > <dinesh_chan8@xxxxxxxxxxx> wrote:
> >
> > Thanks Weiming,
> >
> > But did the same by editing the e820.c. That is,
> > after xen boots up, if I type 'xm dmesg' I could find my output which is
> > (000000000fff000000 - 00000000ffffffff (mypci_usable)).
> >
> > I couldn't find the exact place in xen source where the memory allocation
> > for DomU guests are performed.
> >
> > Now how can I make XEN use the above (mypci_usable) memory range to allocate
> > memory for all its DomU guests.
> >
> > Thanks in advance
> > Dinesh C
> >
> >
> > ________________________________
> > Date: Fri, 6 Jun 2008 15:12:49 -0400
> > From: zephyr.zhao@xxxxxxxxx
> > To: dinesh_chan8@xxxxxxxxxxx
> > CC: xen-devel@xxxxxxxxxxxxxxxxxxx; xen-users@xxxxxxxxxxxxxxxxxxx
> > Subject: [Xen-users] Re: [Xen-devel] Xen - Guest memory allocation
> >
> > I'm not very sure about your problem. Can the Hypervisor address the whole
> > 5GB space? If yes, it can then allocate any of them to guests.
> >
> > Or you can modify the 'start info' passed to Guest OS. You can change the
> > page_nr, a machine-PFN translation table to enable the guest to address the
> > memory space that you want. It's weird.
> >
> > On Fri, Jun 6, 2008 at 2:57 PM, dinesh chandrasekaran
> > <dinesh_chan8@xxxxxxxxxxx> wrote:
> >
> > YES.
> >
> > But if I want to add memory of type E820_USABLE to xen memory map
> > during boot up (as per xen/e820.c) where the memory to be added lies behind
> > a PCI device?
> >
> > For ex,
> > If a PCI device reports it has 1GB of memory behind it.
> > And XEN has identified th RAM memory to be 4GB.
> >
> > How can the PCI - 1GB can be added as usable memory to XEN's memory pool to
> > get a cumulative size of 5GB;
> >
> > thanks,
> > Dinesh C
> >
> > On Fri, Jun 6, 2008 at 3:00 PM, Weiming wrote:
> >
> > AFAIK, In para virtualization, when guest boots, it reads the memorylayout
> > from a special page (start info page) instead of from bios.
> > If your guest os is a PV Linux, you can check its source code (e.g.
> > start_kernel(), etc.)
> >
> > Thanks,
> > Weiming
> >
> > On Fri, Jun 6, 2008 at 2:00 PM, dinesh chandrasekaran
> > <dinesh_chan8@xxxxxxxxxxx> wrote:
> >
> >
> >
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