Messages in this thread | | | Date | Wed, 31 May 2023 19:51:38 +0900 | Subject | Re: [RFC PATCH v2 3/3] PCI: endpoint: Add EP function driver to provide virtio-console functionality | From | Shunsuke Mie <> |
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I'm sorry for late response.
On 2023/05/19 11:01, Jason Wang wrote: > On Thu, May 18, 2023 at 5:54 PM Shunsuke Mie <mie@igel.co.jp> wrote: >> Gentle ping ... >> >> >> Thanks, >> >> Shunsuke. >> >> On 2023/05/10 12:17, Shunsuke Mie wrote: >>> Hi Json, >>> 2023年5月8日(月) 13:03 Jason Wang <jasowang@redhat.com>: >>>> On Thu, Apr 27, 2023 at 6:44 PM Shunsuke Mie <mie@igel.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. >>> Could you tell me what "peer devices" means? > I meant, for example we know in the case of virtio-net, TX can talk > with RX belonging to another device directly. > > But this is not the case for other devices like virito-blk. Thank you. I comprehended it. >>>> 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. >>> Does it mean that the driver also functions as a network driver directly? > I meant, e.g in the case of networking, you can have a dedicated > driver with two vringh in the endpoint side. > > The benefit is the performance, no need for the (datapath) mediation. > > But if we don't care about the performance, this proposal seems to be fine. > > Thanks I agree with you. The design you suggested is better in terms of performance. However, the proposed design is not bad for the following the reasons I think.
The proposed design has one more operation in control plane because the data steps over the virtio-net driver, but the number of copies at the data plane remains the same. I think the operation added in control plane has small effects for performance.
Moreover, there are some advantages when the data step over the virtio-net driver. We can make use of the optimizations and some functions without modifications and implementations. e.g. ethtool and XDP(BPF) supports.
Any comments would be appreciated.
>>>>> 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@igel.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. >>> I'm planning to implement each virtio device in a separate file. >>> https://lwn.net/Articles/922124/ >>> >>> >>> >>>> Thanks >>>> >>> Best regards, >>> Shunsuke
Best regards,
Shunsuke
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