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Date: Wed, 1 Apr 2020 22:50:50 +0800
From: Jason Wang <jasowang@...hat.com>
To: "Michael S. Tsirkin" <mst@...hat.com>
Cc: Christian Borntraeger <borntraeger@...ibm.com>,
linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
jgg@...lanox.com, maxime.coquelin@...hat.com,
cunming.liang@...el.com, zhihong.wang@...el.com,
rob.miller@...adcom.com, xiao.w.wang@...el.com,
lingshan.zhu@...el.com, eperezma@...hat.com, lulu@...hat.com,
parav@...lanox.com, kevin.tian@...el.com, stefanha@...hat.com,
rdunlap@...radead.org, hch@...radead.org, aadam@...hat.com,
jiri@...lanox.com, shahafs@...lanox.com, hanand@...inx.com,
mhabets@...arflare.com, gdawar@...inx.com, saugatm@...inx.com,
vmireyno@...vell.com, zhangweining@...jie.com.cn
Subject: Re: [PATCH V9 1/9] vhost: refine vhost and vringh kconfig
On 2020/4/1 下午10:27, Michael S. Tsirkin wrote:
> On Wed, Apr 01, 2020 at 10:13:29PM +0800, Jason Wang wrote:
>> On 2020/4/1 下午9:02, Christian Borntraeger wrote:
>>> On 01.04.20 14:56, Christian Borntraeger wrote:
>>>> On 01.04.20 14:50, Jason Wang wrote:
>>>>> On 2020/4/1 下午7:21, Christian Borntraeger wrote:
>>>>>> On 26.03.20 15:01, Jason Wang wrote:
>>>>>>> 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.
>>>>>> FWIW, this now results in vhost not being build with defconfig kernels (in todays
>>>>>> linux-next).
>>>>>>
>>>>> Hi Christian:
>>>>>
>>>>> Did you meet it even with this commit https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/?id=a4be40cbcedba9b5b714f3c95182e8a45176e42d?
>>>> I simply used linux-next. The defconfig does NOT contain CONFIG_VHOST and therefore CONFIG_VHOST_NET and friends
>>>> can not be selected.
>>>>
>>>> $ git checkout next-20200401
>>>> $ make defconfig
>>>> HOSTCC scripts/basic/fixdep
>>>> HOSTCC scripts/kconfig/conf.o
>>>> HOSTCC scripts/kconfig/confdata.o
>>>> HOSTCC scripts/kconfig/expr.o
>>>> LEX scripts/kconfig/lexer.lex.c
>>>> YACC scripts/kconfig/parser.tab.[ch]
>>>> HOSTCC scripts/kconfig/lexer.lex.o
>>>> HOSTCC scripts/kconfig/parser.tab.o
>>>> HOSTCC scripts/kconfig/preprocess.o
>>>> HOSTCC scripts/kconfig/symbol.o
>>>> HOSTCC scripts/kconfig/util.o
>>>> HOSTLD scripts/kconfig/conf
>>>> *** Default configuration is based on 'x86_64_defconfig'
>>>> #
>>>> # configuration written to .config
>>>> #
>>>>
>>>> $ grep VHOST .config
>>>> # CONFIG_VHOST is not set
>>>>
>>>>> If yes, what's your build config looks like?
>>>>>
>>>>> Thanks
>>> This was x86. Not sure if that did work before.
>>> On s390 this is definitely a regression as the defconfig files
>>> for s390 do select VHOST_NET
>>>
>>> grep VHOST arch/s390/configs/*
>>> arch/s390/configs/debug_defconfig:CONFIG_VHOST_NET=m
>>> arch/s390/configs/debug_defconfig:CONFIG_VHOST_VSOCK=m
>>> arch/s390/configs/defconfig:CONFIG_VHOST_NET=m
>>> arch/s390/configs/defconfig:CONFIG_VHOST_VSOCK=m
>>>
>>> and this worked with 5.6, but does not work with next. Just adding
>>> CONFIG_VHOST=m to the defconfig solves the issue, something like
>>
>> Right, I think we probably need
>>
>> 1) add CONFIG_VHOST=m to all defconfigs that enables
>> CONFIG_VHOST_NET/VSOCK/SCSI.
>>
>> or
>>
>> 2) don't use menuconfig for CONFIG_VHOST, let NET/SCSI/VDPA just select it.
>>
>> Thanks
> OK I tried this:
>
> diff --git a/drivers/vhost/Kconfig b/drivers/vhost/Kconfig
> index 2523a1d4290a..a314b900d479 100644
> --- a/drivers/vhost/Kconfig
> +++ b/drivers/vhost/Kconfig
> @@ -19,11 +19,10 @@ menuconfig VHOST
> This option is selected by any driver which needs to access
> the core of vhost.
>
> -if VHOST
> -
> config VHOST_NET
> tristate "Host kernel accelerator for virtio net"
> depends on NET && EVENTFD && (TUN || !TUN) && (TAP || !TAP)
> + select VHOST
> ---help---
> This kernel module can be loaded in host kernel to accelerate
> guest networking with virtio_net. Not to be confused with virtio_net
> @@ -35,6 +34,7 @@ config VHOST_NET
> config VHOST_SCSI
> tristate "VHOST_SCSI TCM fabric driver"
> depends on TARGET_CORE && EVENTFD
> + select VHOST
> default n
> ---help---
> Say M here to enable the vhost_scsi TCM fabric module
> @@ -44,6 +44,7 @@ config VHOST_VSOCK
> tristate "vhost virtio-vsock driver"
> depends on VSOCKETS && EVENTFD
> select VIRTIO_VSOCKETS_COMMON
> + select VHOST
> default n
> ---help---
> This kernel module can be loaded in the host kernel to provide AF_VSOCK
> @@ -57,6 +58,7 @@ config VHOST_VDPA
> tristate "Vhost driver for vDPA-based backend"
> depends on EVENTFD
> select VDPA
> + select VHOST
> help
> This kernel module can be loaded in host kernel to accelerate
> guest virtio devices with the vDPA-based backends.
> @@ -78,5 +80,3 @@ config VHOST_CROSS_ENDIAN_LEGACY
> adds some overhead, it is disabled by default.
>
> If unsure, say "N".
> -
> -endif
>
>
> But now CONFIG_VHOST is always "y", never "m".
> Which I think will make it a built-in.
> Didn't figure out why yet.
Is it because the dependency of EVENTFD for CONFIG_VHOST?
Remove that one for this patch, I can get CONFIG_VHOST=m.
But according to documentation/kbuild/kconfig.rst, select is used for
option without prompt.
Thanks
>
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