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Subject: Re: [PATCH V9 1/9] vhost: refine vhost and vringh kconfig
To:     "Michael S. Tsirkin" <mst@redhat.com>
Cc:     Christian Borntraeger <borntraeger@de.ibm.com>,
        linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
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From:   Jason Wang <jasowang@redhat.com>
Message-ID: <45fbf320-90e5-9eed-6f07-c5a4dd2ca8f5@redhat.com>
Date:   Wed, 1 Apr 2020 22:36:08 +0800
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On 2020/4/1 =E4=B8=8B=E5=8D=8810:18, Michael S. Tsirkin wrote:
> On Wed, Apr 01, 2020 at 10:13:29PM +0800, Jason Wang wrote:
>> On 2020/4/1 =E4=B8=8B=E5=8D=889:02, 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 =E4=B8=8B=E5=8D=887:21, Christian Borntraeger wrote:
>>>>>> On 26.03.20 15:01, Jason Wang wrote:
>>>>>>> Currently, CONFIG_VHOST depends on CONFIG_VIRTUALIZATION. But vho=
st 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 ker=
nels (in todays
>>>>>> linux-next).
>>>>>>
>>>>> Hi Christian:
>>>>>
>>>>> Did you meet it even with this commithttps://git.kernel.org/pub/scm=
/linux/kernel/git/next/linux-next.git/commit/?id=3Da4be40cbcedba9b5b714f3=
c95182e8a45176e42d?
>>>> I simply used linux-next. The defconfig does NOT contain CONFIG_VHOS=
T 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=3Dm
>>> arch/s390/configs/debug_defconfig:CONFIG_VHOST_VSOCK=3Dm
>>> arch/s390/configs/defconfig:CONFIG_VHOST_NET=3Dm
>>> arch/s390/configs/defconfig:CONFIG_VHOST_VSOCK=3Dm
>>>
>>> and this worked with 5.6, but does not work with next. Just adding
>>> CONFIG_VHOST=3Dm to the defconfig solves the issue, something like
>> Right, I think we probably need
>>
>> 1) add CONFIG_VHOST=3Dm to all defconfigs that enables
>> CONFIG_VHOST_NET/VSOCK/SCSI.
>>
>> or
>>
>> 2) don't use menuconfig for CONFIG_VHOST, let NET/SCSI/VDPA just selec=
t it.
>>
>> Thanks
> I think I prefer 2, but does it auto-select VHOST_IOTLB then?


I think so. E.g VHOST_NET will select VHOST,=C2=A0 and VHOST will select=20
VHOST_IOTLB.


> Generally what was the reason to drop select VHOST from devices?
>
>

The reason is a sub menu is needed for VHOST devices, then I use=20
menuconfig for CONFIG_VHOST.

Then select is not necessary anymore.

Thanks