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Message-ID: <CACGkMEsjH8fA2r=0CacK8WK_sUTAcTK7SQ_VwkJpa1rSgDP0dg@mail.gmail.com>
Date: Mon, 8 May 2023 12:03:44 +0800
From: Jason Wang <jasowang@...hat.com>
To: Shunsuke Mie <mie@...l.co.jp>
Cc: Lorenzo Pieralisi <lpieralisi@...nel.org>,
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>, 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: Re: [RFC PATCH v2 3/3] PCI: endpoint: Add EP function driver to
provide virtio-console functionality
On Thu, Apr 27, 2023 at 6:44 PM Shunsuke Mie <mie@...l.co.jp> wrote:
>
> Add a new PCIe endpoint function driver that works as a pci virtio-console
> device. The console connect to endpoint side console. It enables to
> communicate PCIe host and endpoint.
>
> Architecture is following:
>
> ┌────────────┐ ┌──────────────────────┬────────────┐
> │virtioe │ │ │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
>
I think it might only works for peer devices like:
net, console or vsock.
So there're many choices here, I'd like to know what's the reason for
you to implement a mediation.
An alternative is to implement a dedicated net, console and vsock
driver for vringh (CAIF somehow works like this). This would have
better performance.
> This driver has two roles. The first is as a PCIe endpoint virtio console
> function, which is implemented using the PCIe endpoint framework and PCIe
> EP virtio helpers. The second is as a virtual virtio console device
> connected to the virtio bus on PCIe endpoint Linux.
>
> Communication between the two is achieved by copying the virtqueue data
> between PCIe root and endpoint, respectively.
>
> This is a simple implementation and does not include features of
> virtio-console such as MULTIPORT, EMERG_WRITE, etc. As a result, each
> virtio console driver only displays /dev/hvc0.
>
> As an example of usage, by setting getty to /dev/hvc0, it is possible to
> login to another host.
>
> Signed-off-by: Shunsuke Mie <mie@...l.co.jp>
> ---
> Changes from v2:
> - Change to use copy functions between kiovs of pci-epf-virtio.
>
> drivers/pci/endpoint/functions/Kconfig | 12 +
> drivers/pci/endpoint/functions/Makefile | 1 +
> drivers/pci/endpoint/functions/pci-epf-vcon.c | 596 ++++++++++++++++++
> 3 files changed, 609 insertions(+)
> create mode 100644 drivers/pci/endpoint/functions/pci-epf-vcon.c
>
> diff --git a/drivers/pci/endpoint/functions/Kconfig b/drivers/pci/endpoint/functions/Kconfig
> index fa1a6a569a8f..9ce2698b67e1 100644
> --- a/drivers/pci/endpoint/functions/Kconfig
> +++ b/drivers/pci/endpoint/functions/Kconfig
> @@ -44,3 +44,15 @@ config PCI_EPF_VIRTIO
> select VHOST_RING_IOMEM
> help
> Helpers to implement PCI virtio Endpoint function
> +
> +config PCI_EPF_VCON
> + tristate "PCI Endpoint virito-console driver"
> + depends on PCI_ENDPOINT
> + select VHOST_RING
> + select PCI_EPF_VIRTIO
> + help
> + PCIe Endpoint virtio-console function implementatino. This module
> + enables to show the virtio-console as pci device to PCIe host side, and
> + another virtual virtio-console device registers to endpoint system.
> + Those devices are connected virtually and can communicate each other.
> +
> diff --git a/drivers/pci/endpoint/functions/Makefile b/drivers/pci/endpoint/functions/Makefile
> index a96f127ce900..b4056689ce33 100644
> --- a/drivers/pci/endpoint/functions/Makefile
> +++ b/drivers/pci/endpoint/functions/Makefile
> @@ -7,3 +7,4 @@ obj-$(CONFIG_PCI_EPF_TEST) += pci-epf-test.o
> obj-$(CONFIG_PCI_EPF_NTB) += pci-epf-ntb.o
> obj-$(CONFIG_PCI_EPF_VNTB) += pci-epf-vntb.o
> obj-$(CONFIG_PCI_EPF_VIRTIO) += pci-epf-virtio.o
> +obj-$(CONFIG_PCI_EPF_VCON) += pci-epf-vcon.o
> diff --git a/drivers/pci/endpoint/functions/pci-epf-vcon.c b/drivers/pci/endpoint/functions/pci-epf-vcon.c
> new file mode 100644
> index 000000000000..31f4247cd10f
> --- /dev/null
> +++ b/drivers/pci/endpoint/functions/pci-epf-vcon.c
> @@ -0,0 +1,596 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * PCI Endpoint function driver to impliment virtio-console device
> + * functionality.
> + */
> +#include <linux/pci-epf.h>
> +#include <linux/virtio_ids.h>
> +#include <linux/virtio_pci.h>
> +#include <linux/virtio_console.h>
> +#include <linux/virtio_ring.h>
> +
> +#include "pci-epf-virtio.h"
> +
> +static int virtio_queue_size = 0x100;
> +module_param(virtio_queue_size, int, 0444);
> +MODULE_PARM_DESC(virtio_queue_size, "A length of virtqueue");
> +
> +struct epf_vcon {
> + /* To access virtqueues on remote host */
> + struct epf_virtio evio;
> + struct vringh_kiov *rdev_iovs;
> +
> + /* To register a local virtio bus */
> + struct virtio_device vdev;
> +
> + /* To access virtqueus of local host driver */
> + struct vringh *vdev_vrhs;
> + struct vringh_kiov *vdev_iovs;
> + struct virtqueue **vdev_vqs;
> +
> + /* For transportation and notification */
> + struct workqueue_struct *task_wq;
> + struct work_struct raise_irq_work, rx_work, tx_work;
> +
> + /* To retain virtio features. It is commonly used local and remote. */
> + u64 features;
> +
> + /* To show a status whether this driver is ready and the remote is connected */
> + bool connected;
> +};
> +
> +enum {
> + VCON_VIRTQUEUE_RX,
> + VCON_VIRTQUEUE_TX,
> + // Should be end of enum
> + VCON_VIRTQUEUE_NUM
> +};
It would be better if we can split the console specific thing out,
then it allows us to do ethernet and vsock in the future.
Thanks
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