Re: [dpdk-dev] [PATCH v5 0/3] support both PIO and MMIO BAR for virtio PMD

[Maxime Coquelin <maxime.coquelin@redhat.com>]

On 10/22/20 5:51 PM, 谢华伟(此时此刻） wrote:
> From: "huawei.xhw" <huawei.xhw@alibaba-inc.com>
> 
> Legacy virtio-pci only supports PIO BAR resource. As we need to create lots of
> virtio devices and PIO resource on x86 is very limited, we expose MMIO BAR.
> 
> Kernel supports both PIO  and MMIO BAR for legacy virtio-pci device. We handles
> different type of BAR in the similar way.
> 
> In previous implementation, with igb_uio we get PIO address from igb_uio
> sysfs entry; with uio_pci_generic, we get PIO address from
> /proc/ioports.
> For PIO/MMIO RW, there is different path for different drivers and arch.
> For VFIO, PIO/MMIO RW is through syscall, which has big performance
> issue.

Regarding the performance issue, do you have some numbers to share?
AFAICS, it can only have an impact on performance when interrupt mode is
used or queue notification is enabled.

Does your HW Virtio implementation requires notification?

Is performance the only issue to have your HW working with Virtio PMD,
or is this series also fixing some functionnal issues?

Best regards,
Maxime

> On X86, it assumes only PIO is supported.
> 
> All of the above is too much twisted.
> This patch unifies the way to get both PIO and MMIO address for different driver
> and arch, all from standard resource attr under pci sysfs.
> 
> We distinguish PIO and MMIO by their address like how kernel does. It is ugly but works.
> 
> v2 changes:
> 	 - add more explanation in the commit message
> 
> v3 changes:
> 	 - fix patch format issues
> 
> v4 changes:
> 	 - fixes for RTE_KDRV_UIO_GENERIC -> RTE_PCI_KDRV_UIO_GENERIC
> 
> v5 changes:
> 	 - split into three seperate patches
> 
> huawei.xhw (3):
>   PCI: use PCI standard sysfs entry to get PIO address
>   PCI: support MMIO in rte_pci_ioport_map/unap/read/write
>   PCI: don't use vfio ioctl call to access PIO resource
> 
>  drivers/bus/pci/linux/pci.c     |  89 +-------------------
>  drivers/bus/pci/linux/pci_uio.c | 177 ++++++++++++++++++++++++++++------------
>  2 files changed, 128 insertions(+), 138 deletions(-)
>