Hi again,

I debugged the kernel codes and found out the root cause.
The sharing is not done for some pages causing error -E2BIG which is due to
reference count being more than one. This prevents hypervor to nominate the
page. As much as I know about this issue, the page that I want to nominate
and I receive this error from make_page_sharable function in mem_sharing.c
is pointed by more than one pages. So, is there any idea to resolve this
issue? I though that I can put the page number in a buffer and share it
again after t milliseconds but still the nomination return -E2BIG error.
Am I missing something?

I would be grateful if you could help.


On Sat, Jul 28, 2018 at 11:13 AM sepanta s <sapanta992@gmail.com> wrote:

> Thanks.
> I would be thankful if he can help me ...
>
> On Mon, Jul 23, 2018 at 11:52 AM Razvan Cojocaru <
> rcojocaru@bitdefender.com> wrote:
>
>> On 07/23/2018 05:37 AM, sepanta s wrote:
>> > I have written a program that can share memory pages of two VMs every x
>> > milliseconds. To do so, I modified xen and added an unshare event to be
>> > able to capture it. However,  for some pages, when I receive the unshare
>> > event that contains the information about the pages which was about to
>> > be written on and put it on a buffer for sharing them again after x
>> > milliseconds, I cannot nominate them again and an error occurs. So, the
>> > sharing mechanism I have built can partially share pages. I guess the
>> > problem might be because of internal structure of sharing mechanism in
>> > the Xen but can't figure out the problem.
>> > Do you  have any idea what can cause this problem? Or what should I
>> > check to get closer to any solution?
>>
>> I've never used this feature, but Tamas might have some insight into
>> this (added to Cc).
>>
>