On Fri, Aug 5, 2016 at 5:35 AM, sepanta s wrote: > > > On Tue, Aug 2, 2016 at 8:23 PM, Tamas K Lengyel > wrote: > >> >> >> On Tue, Aug 2, 2016 at 12:19 AM, sepanta s wrote: >> >>> >>> >>> On Sat, Jul 23, 2016 at 3:49 PM, sepanta s 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