linux-kernel - Re: [EXT] [RFC PATCH 0/3] Introduce a PCIe endpoint virtio console

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Date:   Mon, 17 Apr 2023 11:11:46 +0900
From:   Shunsuke Mie <mie@...l.co.jp>
To:     Frank Li <frank.li@....com>,
        Lorenzo Pieralisi <lpieralisi@...nel.org>
Cc:     Krzysztof Wilczyński <kw@...ux.com>,
        Manivannan Sadhasivam <mani@...nel.org>,
        Kishon Vijay Abraham I <kishon@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>, Jon Mason <jdmason@...zu.us>,
        Randy Dunlap <rdunlap@...radead.org>,
        Ren Zhijie <renzhijie2@...wei.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "virtualization@...ts.linux-foundation.org" 
        <virtualization@...ts.linux-foundation.org>
Subject: Re: [EXT] [RFC PATCH 0/3] Introduce a PCIe endpoint virtio console


On 2023/04/14 23:39, Frank Li wrote:
>
>> -----Original Message-----
>> From: Shunsuke Mie <mie@...l.co.jp>
>> Sent: Friday, April 14, 2023 7:39 AM
>> To: Lorenzo Pieralisi <lpieralisi@...nel.org>
>> Cc: Krzysztof Wilczyński <kw@...ux.com>; Manivannan Sadhasivam
>> <mani@...nel.org>; Kishon Vijay Abraham I <kishon@...nel.org>; Bjorn
>> Helgaas <bhelgaas@...gle.com>; Michael S. Tsirkin <mst@...hat.com>;
>> Jason Wang <jasowang@...hat.com>; Shunsuke Mie <mie@...l.co.jp>;
>> Frank Li <frank.li@....com>; Jon Mason <jdmason@...zu.us>; Randy
>> Dunlap <rdunlap@...radead.org>; Ren Zhijie <renzhijie2@...wei.com>;
>> linux-kernel@...r.kernel.org; linux-pci@...r.kernel.org;
>> virtualization@...ts.linux-foundation.org
>> Subject: [EXT] [RFC PATCH 0/3] Introduce a PCIe endpoint virtio console
>>
>> Caution: EXT Email
>>
>> PCIe endpoint framework provides APIs to implement PCIe endpoint
>> function.
>> This framework allows defining various PCIe endpoint function behaviors in
>> software. This patch extend the framework for virtio pci device. The
>> virtio is defined to communicate guest on virtual machine and host side.
>> Advantage of the virtio is the efficiency of data transfer and the conciseness
>> of implementation device using software. It also be applied to PCIe
>> endpoint function.
>>
>> We designed and implemented a PCIe EP virtio console function driver using
>> the extended PCIe endpoint framework for virtio. It can be communicate
>> host and endpoint over virtio as console.
>>
>> An architecture of the function driver is following:
>>
>>   ┌────────────┐         ┌──────────────
>> ────────┬────────────┐
>>   │virtio      │         │                      │virtio      │
>>   │console drv │         ├───────────────┐      │console
>> drv │
>>   ├────────────┤         │(virtio console│      ├─────
>> ───────┤
>>   │ virtio bus │         │ device)       │◄────►│ virtio bus │
>>   ├────────────┤         ├---------------┤      └──────
>> ──────┤
>>   │            │         │ pci ep virtio │                   │
>>   │  pci bus   │         │  console drv  │                   │
>>   │            │  pcie   ├───────────────┤                   │
>>   │            │ ◄─────► │  pci ep Bus   │                   │
>>   └────────────┘         └──────────────
>> ─┴───────────────────┘
>>     PCIe Root              PCIe Endpoint
>>
> [Frank Li] Some basic question,
> I see you call register_virtio_device at epf_vcon_setup_vdev,
> Why call it as virtio console?  I suppose it should be virtiobus directly?

I'm sorry I didn't understand your question. What do you mean the 
virtiobus directly?

>
> Previous you use virtio-net, why change to virtio-console here?  Does it matter?

No, it doesn't. Just I'd like to break down the changes into smaller 
steps to make it easier to review and merge the changes.

As a first step, I propose adding a simplest virtio function driver with 
the extension defined in pci-epf-virtio.{h,c}.

> All virtio-XXX should work?
Yes, the extension is designed to use any type of virtio device.
>
> You removed EDMA support this version?
I planed the support will be added with epf virtio-net patches.
>
>> Introduced driver is `pci ep virtio console drv` in the figure. It works
>> as ep function for PCIe root and virtual virtio console device for PCIe
>> endpoint. Each side of virtio console driver has virtqueue, and
>> introduced driver transfers data on the virtqueue to each other. A data
>> on root tx queue is transfered to endpoint rx queue and vice versa.
>>
>> This patchset is depend follwing patches which are under discussion.
>>
>> - [RFC PATCH 0/3] Deal with alignment restriction on EP side
>> link:
>> https://lore.k/
>> ernel.org%2Flinux-pci%2F20230113090350.1103494-1-
>> mie%40igel.co.jp%2F&data=05%7C01%7CFrank.Li%40nxp.com%7Cea6513dbf
>> 4084b80ced208db3ce54133%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7
>> C0%7C638170727558800720%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4w
>> LjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C
>> %7C%7C&sdata=jYgy%2Bxk84ZXZRVfqm0GCXoRnCTLMrX4zTfV%2Bs5Mmsvo
>> %3D&reserved=0
>> - [RFC PATCH v2 0/7] Introduce a vringh accessor for IO memory
>> link:
>> https://lore.k/
>> ernel.org%2Fvirtualization%2F20230202090934.549556-1-
>> mie%40igel.co.jp%2F&data=05%7C01%7CFrank.Li%40nxp.com%7Cea6513dbf
>> 4084b80ced208db3ce54133%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7
>> C0%7C638170727558800720%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4w
>> LjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C
>> %7C%7C&sdata=K4El76GSAGtsWkNBXJK5%2Fn7flCN20eEMZpZYTX2WIZ0%3
>> D&reserved=0
>>
>> First of this patchset is introduce a helper function to realize pci
>> virtio function using PCIe endpoint framework. The second one is adding
>> a missing definition for virtio pci header. The last one is for PCIe
>> endpoint virtio console driver.
>>
>> This is tested on linux-20230406 and RCar S4 board as PCIe endpoint.
>>
>> Shunsuke Mie (3):
>>    PCI: endpoint: introduce a helper to implement pci ep virtio function
>>    virtio_pci: add a definition of queue flag in ISR
>>    PCI: endpoint: Add EP function driver to provide virtio-console
>>      functionality
>>
>>   drivers/pci/endpoint/functions/Kconfig        |  19 +
>>   drivers/pci/endpoint/functions/Makefile       |   2 +
>>   drivers/pci/endpoint/functions/pci-epf-vcon.c | 554 ++++++++++++++++++
>>   .../pci/endpoint/functions/pci-epf-virtio.c   | 469 +++++++++++++++
>>   .../pci/endpoint/functions/pci-epf-virtio.h   | 123 ++++
>>   include/uapi/linux/virtio_pci.h               |   3 +
>>   6 files changed, 1170 insertions(+)
>>   create mode 100644 drivers/pci/endpoint/functions/pci-epf-vcon.c
>>   create mode 100644 drivers/pci/endpoint/functions/pci-epf-virtio.c
>>   create mode 100644 drivers/pci/endpoint/functions/pci-epf-virtio.h
>>
>> --
>> 2.25.1