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From: David Hildenbrand <david@redhat.com>
To: Igor Mammedov <imammedo@redhat.com>, Pankaj Gupta <pagupta@redhat.com>
Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
	qemu-devel@nongnu.org, linux-nvdimm@ml01.01.org,
	linux-mm@kvack.org, kwolf@redhat.com, haozhong.zhang@intel.com,
	jack@suse.cz, xiaoguangrong.eric@gmail.com, riel@surriel.com,
	niteshnarayanlal@hotmail.com, ross.zwisler@intel.com,
	lcapitulino@redhat.com, hch@infradead.org, mst@redhat.com,
	stefanha@redhat.com, marcel@redhat.com, pbonzini@redhat.com,
	dan.j.williams@intel.com, nilal@redhat.com
Subject: Re: [Qemu-devel] [RFC v2 0/2] kvm "fake DAX" device flushing
Date: Mon, 4 Jun 2018 11:55:33 +0200	[thread overview]
Message-ID: <a36137df-d2f6-39d5-318e-9006415b8ca2@redhat.com> (raw)
In-Reply-To: <20180601142410.5c986f13@redhat.com>

On 01.06.2018 14:24, Igor Mammedov wrote:
> On Wed, 25 Apr 2018 16:54:12 +0530
> Pankaj Gupta <pagupta@redhat.com> wrote:
> 
> [...]
>> - Qemu virtio-pmem device
>>   It exposes a persistent memory range to KVM guest which 
>>   at host side is file backed memory and works as persistent 
>>   memory device. In addition to this it provides virtio 
>>   device handling of flushing interface. KVM guest performs
>>   Qemu side asynchronous sync using this interface.
> a random high level question,
> Have you considered using a separate (from memory itself)
> virtio device as controller for exposing some memory, async flushing.
> And then just slaving pc-dimm devices to it with notification/ACPI
> code suppressed so that guest won't touch them?

I don't think slaving pc-dimm would be the right thing to do (e.g.
slots, pcdimm vs nvdimm, bus(less), etc..). However the general idea is
interesting for virtio-pmem (as we might have a bigger number of disks).

We could have something like a virtio-pmem-bus to which you attach
virtio-pmem devices. By specifying the mapping, e.g. the thread that
will be used for async flushes will be implicit.

> 
> That way it might be more scale-able, you consume only 1 PCI slot
> for controller vs multiple for virtio-pmem devices.>
> 
>> Changes from previous RFC[1]:
>>
>> - Reuse existing 'pmem' code for registering persistent 
>>   memory and other operations instead of creating an entirely 
>>   new block driver.
>> - Use VIRTIO driver to register memory information with 
>>   nvdimm_bus and create region_type accordingly. 
>> - Call VIRTIO flush from existing pmem driver.
>>
>> Details of project idea for 'fake DAX' flushing interface is 
>> shared [2] & [3].
>>
>> Pankaj Gupta (2):
>>    Add virtio-pmem guest driver
>>    pmem: device flush over VIRTIO
>>
>> [1] https://marc.info/?l=linux-mm&m=150782346802290&w=2
>> [2] https://www.spinics.net/lists/kvm/msg149761.html
>> [3] https://www.spinics.net/lists/kvm/msg153095.html  
>>
>>  drivers/nvdimm/region_devs.c     |    7 ++
>>  drivers/virtio/Kconfig           |   12 +++
>>  drivers/virtio/Makefile          |    1 
>>  drivers/virtio/virtio_pmem.c     |  118 +++++++++++++++++++++++++++++++++++++++
>>  include/linux/libnvdimm.h        |    4 +
>>  include/uapi/linux/virtio_ids.h  |    1 
>>  include/uapi/linux/virtio_pmem.h |   58 +++++++++++++++++++
>>  7 files changed, 201 insertions(+)
>>
> 


-- 

Thanks,

David / dhildenb

      parent reply	other threads:[~2018-06-04  9:55 UTC|newest]

Thread overview: 33+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-25 11:24 Pankaj Gupta
2018-04-25 11:24 ` [RFC v2 1/2] virtio: add pmem driver Pankaj Gupta
2018-04-25 14:21   ` Dan Williams
2018-04-25 14:43     ` Dan Williams
2018-04-26 12:27       ` Jeff Moyer
2018-04-26 17:15         ` [Qemu-devel] " Pankaj Gupta
2018-04-26 17:24           ` Jeff Moyer
2018-04-25 14:52   ` Michael S. Tsirkin
2018-04-25 15:11     ` [Qemu-devel] " Pankaj Gupta
2018-04-26 13:12   ` Stefan Hajnoczi
2018-04-26 15:44     ` Pankaj Gupta
2018-04-27 13:31       ` Stefan Hajnoczi
2018-04-28 10:48         ` Pankaj Gupta
2018-04-25 11:24 ` [RFC v2 2/2] pmem: device flush over VIRTIO Pankaj Gupta
2018-04-25 14:23   ` Dan Williams
2018-04-25 14:47     ` Pankaj Gupta
2018-04-26 13:15   ` Stefan Hajnoczi
2018-04-26 16:40     ` Pankaj Gupta
2018-04-26 16:57       ` Dan Williams
2018-04-26 17:13         ` Pankaj Gupta
2018-04-25 11:24 ` [RFC v2] qemu: Add virtio pmem device Pankaj Gupta
2018-04-25 11:35   ` [Qemu-devel] " no-reply
2018-04-25 11:58     ` Pankaj Gupta
2018-04-25 14:23       ` Eric Blake
2018-04-25 14:51         ` Pankaj Gupta
2018-04-25 11:46   ` no-reply
2018-04-25 14:25   ` Eric Blake
2018-04-25 14:55     ` Pankaj Gupta
2018-04-26 13:24   ` Stefan Hajnoczi
2018-04-26 16:43     ` [Qemu-devel] " Pankaj Gupta
2018-06-01 12:24 ` [Qemu-devel] [RFC v2 0/2] kvm "fake DAX" device flushing Igor Mammedov
2018-06-04  5:56   ` Pankaj Gupta
2018-06-04  9:55   ` David Hildenbrand [this message]

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