Re: [Xen-users] Re: [Xen-devel] Xen - Guest memory allocation

["Derek Murray" <Derek.Murray@xxxxxxxxxxxx>]

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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