Re: Fw: somthing new for shared memory???

Izik Eidus
2007-10-25T22:51:54Z

Francesco Cipollone wrote:
> ----- Original Message -----
> From: "Francesco Cipollone" <francesco.cipo-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
> To: "Izik Eidus" <izike-atKUWr5tajBWk0Htik3J/w@public.gmane.org>
> Sent: Thursday, October 25, 2007 10:43 PM
> Subject: Re: [kvm-devel] somthing new for shared memory???
>
>
>
>> ----- Original Message -----
>> From: "Izik Eidus" <izike-atKUWr5tajBWk0Htik3J/w@public.gmane.org>
>> To: "Francesco Cipollone" <francesco.cipo-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
>> Sent: Thursday, October 25, 2007 11:25 PM
>> Subject: Re: [kvm-devel] somthing new for shared memory???
>>
>>
>>
>>> Francesco Cipollone wrote:
>>>
>>>> can you gently explain more about the second option
>>>>
>>>> ----- Original Message ----- From: "Izik Eidus" <izike-atKUWr5tajBWk0Htik3J/w@public.gmane.org>
>>>> To: "Francesco Cipollone" <francesco.cipo-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
>>>> Cc: <kvm-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org>
>>>> Sent: Thursday, October 25, 2007 11:03 PM
>>>> Subject: Re: [kvm-devel] somthing new for shared memory???
>>>>
>>>>
>>>>
>>>>> Francesco Cipollone wrote:
>>>>>
>>>>>> Hy
>>>>>> somthing new about the shared memory support between VMs? or VM and
>>>>>> host?
>>>>>> bye
>>>>>>
>>>>>>
>>>>> beside moving the memory allocation to userspace (this is first step in
>>>>> share memory between VMs using smart file system)
>>>>> there is not much advance.
>>>>>
>>>>> about sharing memory between VM and host, we improved it by adding
>>>>> partial swapping support,
>>>>> so the host can take memory from the guest in demand.
>>>>>
>>>> can you gently explain to me more abouth this option?
>>>> thank you very much
>>>> Francesco
>>>>
>>> this option (guest swapping) run by default, it have two good effect:
>>> 1.part of the unused memory of the guest can be swapped (the kernel treat
>>> this area of memory as of normal process memory and swap it
>>> on deamed) it allow you to allocate VMs with more ram than you have on
>>> host.
>>> 2.memory is allocated on deamed, this make VM load faster and dont steal
>>> memory that it dont touch
>>>
>>> about the "partial swapping" to make it short:
>>> there is as for now (we will fix this) amount of memory that is mapped
>>> inside kvm that cant be swapped,
>>> it is hard to tell how much would it be, but from tests that i made i saw
>>> that most of times (infact i never saw case when this is not true) guests
>>> give up about 90%+ of their ram when the host asked for.
>>>
>> So if i want to share a part of memory (for example i allocate it in
>> kernel-space, in guest, with a module)
>> and tell the host an address, can this one see it?
>> I want to make a sort of sharing memory between host and guest, an
>> unidirection channel,with a signal channel or somthing like that
>> to wake up the host when there is somthing new to read in the shared
>> memory.
>> I want to do somthing like this becouse this application is almost
>> invisible...
>> is for a security application
>> can you help me do that?
>> I don't undestand if i can share a part of the phisical memory of the
>> guest with the host.
>>
>> thanks
>> Francesco
>>
>>
ohh, i see, i probably misslead you, this isnt swapping what you want
you want just to read the guest memory,

in this case you can do both of the things you talked about,
you can allocate mapped file to few guests (this way the guests will
have shared memory between them that they would be able to see)

and for the host, all you have to do is to read the guest memory
(if you use qemu use:phys_ram_base + offset, and if you want to do it
from kvmctl, check out kvm->physical_memory)

i can help if you make it more specific.
>>>
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>>>>>>
>>>>>>
>
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