On Tue, Aug 2, 2016 at 8:23 PM, Tamas K Lengyel <ta...@tklengyel.com> wrote:
>
>
> On Tue, Aug 2, 2016 at 12:19 AM, sepanta s <sapanta...@gmail.com> wrote:
>
>>
>>
>> On Sat, Jul 23, 2016 at 3:49 PM, sepanta s <sapanta...@gmail.com> wrote:
>>
>>>
>>>>> Hi,
>>>>> Is there any sample code which I can undestand how to capture the
>>>>> events on the gfns which have p2m_ram_shared enabled ?
>>>>> I couldn't find any ... .
>>>>> I would be grateful if any help , as there is not any documents
>>>>> through net to use :(
>>>>>
>>>>>
>>>> Should I just set the ring_page as the pages which are shared and mark
>>>>> them read-only, then capture the write events?
>>>>>
>>>>
>>>> Not sure what ring_page you are talking about, but if you mark the
>>>> pages read-only with mem_access you will get notifications for events that
>>>> lead to unsharing with p2m_ram_shared type pages as well.
>>>>
>>>
>>> There was a function in mem-sharing.c which is intended to announce the
>>> failed unshared pages. It is "mem_sharing_notify_enomem" .
>>> I added "mem_sharing_notify_unshare" as a new function and call it in
>>> also XEN_DOMCTL_VM_EVENT_OP_UNSHARING and "HVM_PARAM_USHARING_RING_PFN".
>>> I also added the required codes in /xen/common/vm_event.c and
>>> /tools/libxc/xc_vm_event so as
>>> I have added a new event for the unsharing actions of a page.
>>> Then, I wrote a sample code line xen-access and create a ring for the
>>> pages of a domain and listen to unshared events of it.
>>>
>>>>
>>>>> BTW, I added a function called mem_sharing_notify_unshare to
>>>>> mem_sharing.c and added it to __mem_sharing_unshare_page at this part:
>>>>>
>>>>> *if ( p2m_change_type_one(d, gfn, p2m_ram_shared, p2m_ram_rw) )*
>>>>> *{*
>>>>> *gdprintk(XENLOG_ERR, "Could not change p2m type d %hu gfn %lx.\n", *
>>>>> *d->domain_id, gfn);*
>>>>> *BUG();*
>>>>> *}else {*
>>>>>
>>>>>
>>>>> * mem_sharing_notify_unshare(d,gfn.0);*
>>>>> *}*
>>>>>
>>>>>
>>>> IMHO this duplicates a lot of what mem_access does already, I don't
>>>> think there is a need for a separate notification on another ring.
>>>>
>>>>
>>> You are right, xen-access should work but I couldn't change its code and
>>> couldn't get the mem-access events.
>>> I just added the above function to be sure that unsharing a page
>>> happens and works fine. Because I couldn't get the access requests on
>>> shared-pages of a vm.
>>> In xen-access, Instead of setting all the pages' default access to rx ,
>>> I just call xc_set_mem_access for the pages with p2m_ram_shared and assign
>>> rx as the default access but there is no requests on this ring.
>>>
>>>>
>>>
>>> So by having a vm event channel listening to unsharing event, I can see
>>>>> the notification in xen-access . To do so, I
>>>>> have used vm_event_enable which uses HVM_PARAM_SHARING_RING_PFN .
>>>>> But, when I used memshrtool to share all the pages of two vms - my vm1
>>>>> and its clone vm2 .
>>>>> About 900 MB of the ram is shared but there are a lot of unshared
>>>>> events happening.
>>>>>
>>>>
>>>> Yes, I would say that's expected.
>>>>
>>>
>>>>
>>>>> When I do the sharing one more time, there is not any pages unshared
>>>>> as the total number of shared pages stay the same.
>>>>>
>>>>
>>>> Well, if you let the domain run for a while after sharing, then you do
>>>> the sharing like that again you are likely going to crash the VM.
>>>>
>>>>
>>>>> Seems no unsharing is done as the number of shared pages are the same.
>>>>> Does any page fault triggers when a write operation is done on a
>>>>> shared page among two vms ?
>>>>>
>>>>
>>>> I would guess the the VM crashed and that's why you don't see any more
>>>> unsharing at that point.
>>>>
>>> Yes it was crashed as I checked it.
>>> The scenario of sharing is I use:
>>> I pause the origin VM and then run memshrtool on origin VM and clone VM.
>>> After sharing all the pages between these two VMs,Clone VM seems to be
>>> inaccessible. The clone seems to work as the attached photo shows, its cpu
>>> time increases and it exceeds the dom0 cpu time but when I use gvncviewer
>>> to see the GUI of the Clone VM, the mouse or keyboard don't work. (origin
>>> VM is ubunut-64-1 and clone VM is ubuntu-64-clone-1). Is there anything I
>>> have missed in sharing between two VMs?
>>>
>>> [image: Inline image 2]
>>>
>>
>> Can someone help please ? still have problem with the machine .
>> is it because sharing is not based on content?
>>
>>
> Well, the emulated device contexts probably get all messed up when you
> just clone over the memory of the domain and that's why they don't work.
> The only way I got this to work is by doing a save/restore of the origin
> domain before doing the memory sharing.
>
> Tamas
>
I do so , as I use the following commands to create the clone :
xl save -c origin-domid /tmp/clone
xl restore -p -e /etc/xen/clone.config /tmp/clone
Also I keep the origin and clone both unpaused before sharing and after
that, I just unpause the clone , but I
can just run some commands and then the clone stops responding to mouse
operations.
My vms are both ubuntu-14.04 LTS.
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