Re: vhost: refine vhost and vringh kconfig

[Jason Wang <jasowang@redhat.com>]

On 2020/4/10 下午3:53, Geert Uytterhoeven wrote:
> Hi Jason,
>
> On Thu, Apr 9, 2020 at 6:04 AM Linux Kernel Mailing List
> <linux-kernel@vger.kernel.org> wrote:
>> Commit:     20c384f1ea1a0bc7320bc445c72dd02d2970d594
>> Parent:     5a6b4cc5b7a1892a8d7f63d6cbac6e0ae2a9d031
>> Refname:    refs/heads/master
>> Web:        https://git.kernel.org/torvalds/c/20c384f1ea1a0bc7320bc445c72dd02d2970d594
>> Author:     Jason Wang <jasowang@redhat.com>
>> AuthorDate: Thu Mar 26 22:01:17 2020 +0800
>> Committer:  Michael S. Tsirkin <mst@redhat.com>
>> CommitDate: Wed Apr 1 12:06:26 2020 -0400
>>
>>      vhost: refine vhost and vringh kconfig
>>
>>      Currently, CONFIG_VHOST depends on CONFIG_VIRTUALIZATION. But vhost is
>>      not necessarily for VM since it's a generic userspace and kernel
>>      communication protocol. Such dependency may prevent archs without
>>      virtualization support from using vhost.
>>
>>      To solve this, a dedicated vhost menu is created under drivers so
>>      CONIFG_VHOST can be decoupled out of CONFIG_VIRTUALIZATION.
>>
>>      While at it, also squash Kconfig.vringh into vhost Kconfig file. This
>>      avoids the trick of conditional inclusion from VOP or CAIF. Then it
>>      will be easier to introduce new vringh users and common dependency for
>>      both vringh and vhost.
>>
>>      Signed-off-by: Jason Wang <jasowang@redhat.com>
>>      Link: https://lore.kernel.org/r/20200326140125.19794-2-jasowang@redhat.com
>>      Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
>> ---
>>   arch/arm/kvm/Kconfig         |  2 --
>>   arch/arm64/kvm/Kconfig       |  2 --
>>   arch/mips/kvm/Kconfig        |  2 --
>>   arch/powerpc/kvm/Kconfig     |  2 --
>>   arch/s390/kvm/Kconfig        |  4 ----
>>   arch/x86/kvm/Kconfig         |  4 ----
>>   drivers/Kconfig              |  2 ++
>>   drivers/misc/mic/Kconfig     |  4 ----
>>   drivers/net/caif/Kconfig     |  4 ----
>>   drivers/vhost/Kconfig        | 28 +++++++++++++++++++++-------
>>   drivers/vhost/Kconfig.vringh |  6 ------
>>   11 files changed, 23 insertions(+), 37 deletions(-)
>> --- a/drivers/vhost/Kconfig
>> +++ b/drivers/vhost/Kconfig
>> @@ -1,4 +1,23 @@
>>   # SPDX-License-Identifier: GPL-2.0-only
>> +config VHOST_RING
>> +       tristate
>> +       help
>> +         This option is selected by any driver which needs to access
>> +         the host side of a virtio ring.
>> +
>> +config VHOST
>> +       tristate
>> +       select VHOST_IOTLB
>> +       help
>> +         This option is selected by any driver which needs to access
>> +         the core of vhost.
>> +
>> +menuconfig VHOST_MENU
>> +       bool "VHOST drivers"
>> +       default y
> Please do not use default y. Your subsystem is not special.


This is because before this patch VHOST depends on VIRTUALIZATION. So 
the archs whose defconfig that has VIRTUALIZATION can just enable e.g 
VHOST_NET without caring about VHOST_MENU.

If this is not preferable, we can:

1) modify the defconfig and enable VHOST_MENU there
2) switch to use default y if $(all_archs_that_has_VIRTUALIZATION)


>
>> +
> I think this deserves a help text, so users know if they want to enable this
> option or not.


Will add one.

Thanks


>
> Thanks!
>
>> +if VHOST_MENU
>> +
>>   config VHOST_NET
>>          tristate "Host kernel accelerator for virtio net"
>>          depends on NET && EVENTFD && (TUN || !TUN) && (TAP || !TAP)
> Gr{oetje,eeting}s,
>
>                          Geert
>
>
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
>
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like that.
>                                  -- Linus Torvalds
>