Re: [PATCH V9 1/9] vhost: refine vhost and vringh kconfig

[Jason Wang]

On 2020/4/1 äå10:18, Michael S. Tsirkin wrote:
> On Wed, Apr 01, 2020 at 10:13:29PM +0800, Jason Wang wrote:
> > On 2020/4/1 äå9:02, 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 äå7:21, 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 commithttps://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
> I think I prefer 2, but does it auto-select VHOST_IOTLB then?


I think so. E.g VHOST_NET will select VHOST, and VHOST will select 
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 
menuconfig for CONFIG_VHOST.

Then select is not necessary anymore.

Thanks