On Fri, Aug 5, 2016 at 5:35 AM, sepanta s <sapanta...@gmail.com> wrote:
>
>
> 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.
>
I guess you mean you keep both of them paused before sharing, and after
sharing you only unpause the clone. I'm not sure xl save -c will keep the
domain paused after it is saved though. Also, in my experience you have to
restore _both_ the origin and the clone domain from a save state for this
to work flawlessly. Underlying reason for this is unknown, I haven't
investigated further into it after finding at least one way to get it
working.
Tamas
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