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

[Shunsuke Mie <mie@xxxxxxxxxx>]

On 2023/04/14 23:39, Frank Li wrote:
> > -----Original Message-----
> > From: Shunsuke Mie <mie@xxxxxxxxxx>
> > Sent: Friday, April 14, 2023 7:39 AM
> > To: Lorenzo Pieralisi <lpieralisi@xxxxxxxxxx>
> > Cc: Krzysztof Wilczyński <kw@xxxxxxxxx>; Manivannan Sadhasivam
> > <mani@xxxxxxxxxx>; Kishon Vijay Abraham I <kishon@xxxxxxxxxx>; Bjorn
> > Helgaas <bhelgaas@xxxxxxxxxx>; Michael S. Tsirkin <mst@xxxxxxxxxx>;
> > Jason Wang <jasowang@xxxxxxxxxx>; Shunsuke Mie <mie@xxxxxxxxxx>;
> > Frank Li <frank.li@xxxxxxx>; Jon Mason <jdmason@xxxxxxxx>; Randy
> > Dunlap <rdunlap@xxxxxxxxxxxxx>; Ren Zhijie <renzhijie2@xxxxxxxxxx>;
> > linux-kernel@xxxxxxxxxxxxxxx; linux-pci@xxxxxxxxxxxxxxx;
> > virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx
> > 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