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Message-Id: <cc3ef7f5-2980-00bf-2534-272b882bb64f@de.ibm.com>
Date: Wed, 1 Apr 2020 20:53:25 +0200
From: Christian Borntraeger <borntraeger@...ibm.com>
To: "Michael S. Tsirkin" <mst@...hat.com>,
Jason Wang <jasowang@...hat.com>
Cc: 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 01.04.20 17:57, Michael S. Tsirkin wrote:
> On Wed, Apr 01, 2020 at 10:50:50PM +0800, Jason Wang wrote:
>>
>> 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?
>
> Oh no, it's because I forgot to change menuconfig to config.
>
>
>> Remove that one for this patch, I can get CONFIG_VHOST=m.
FWIW, the current vhost/linux-next branch seems to work again.
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