Re: [Qemu-devel] [PATCH RFCv2 0/9] qdev: Hotplug handler chaining + virtio-pmem

[David Hildenbrand <david@redhat.com>]

On 28.01.19 15:18, Igor Mammedov wrote:
> On Wed, 23 Jan 2019 20:55:18 +0100
> David Hildenbrand <david@redhat.com> wrote:
> 
>> This series implements supprt for hotplug handler chaining (proposed
>> by Igor), something that is necessary to turn selected virtio devices into
>> memory devices. Planned devices inlude virtio-mem and virtio-pmem. The
>> current prototype of virtio-pmem is included.
>>
>> The machine hotplug handler can intercept hotplug handler calls
>> to properly prepare/teardown the memory device part of a device. Control
>> is then passed on to the actual bus hotplug handler. So the default hotplug
>> handler is effectively overwritten to make interception possible.
>>
>> It is based on the following patches/series
>> - [PATCH v1] pc: Use hotplug_handler_(plug|unplug|unplug_request)
>> -- Queued by Paolo
>> - [PATCH v3 0/2] s390x/pci: hotplug handler fixes and reworks
>>
>> Patch 1-3 are the preparations for hotplug handler chaining.
> we probably should merge this ones even without pmem patches.

Sounds good to me. I'll do more testing.

> 
>> The remaining patches are a modified prototype of virtio-pmem.
> I'm not sure yet that virtio-pmem should be merged.
> 
> Initial goal for fake pmem was to eliminate page-cache in guest
> so that only host will have it and cached pages could be shared
> between several guest.
> 
> However recently (if I read kernel driver thread right),
> sharing is to be disabled due to security implication and then
> only dropping page cache on one side is left, which could be done
> using existing frontends/backends (disabling caching on host side).
> 

Yes, we should at least wait for the kernel part to settle. Anyhow, I
will base my virtio-mem work on this in a very similar fashion!

Thanks Igor!


-- 

Thanks,

David / dhildenb