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Date:   Wed, 1 Apr 2020 10:39:21 -0400
From:   "Michael S. Tsirkin" <mst@redhat.com>
To:     Jason Wang <jasowang@redhat.com>
Cc:     linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
        virtualization@lists.linux-foundation.org, netdev@vger.kernel.org,
        jgg@mellanox.com, maxime.coquelin@redhat.com,
        cunming.liang@intel.com, zhihong.wang@intel.com,
        rob.miller@broadcom.com, xiao.w.wang@intel.com,
        lingshan.zhu@intel.com, eperezma@redhat.com, lulu@redhat.com,
        parav@mellanox.com, kevin.tian@intel.com, stefanha@redhat.com,
        rdunlap@infradead.org, hch@infradead.org, aadam@redhat.com,
        jiri@mellanox.com, shahafs@mellanox.com, hanand@xilinx.com,
        mhabets@solarflare.com, gdawar@xilinx.com, saugatm@xilinx.com,
        vmireyno@marvell.com, zhangweining@ruijie.com.cn
Subject: Re: [PATCH V9 1/9] vhost: refine vhost and vringh kconfig
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On Wed, Apr 01, 2020 at 10:29:32PM +0800, Jason Wang wrote:
> 
> On 2020/4/1 下午10:13, Michael S. Tsirkin wrote:
> > On Wed, Apr 01, 2020 at 10:08:59PM +0800, Jason Wang wrote:
> > > On 2020/4/1 下午9:22, Michael S. Tsirkin wrote:
> > > > On Thu, Mar 26, 2020 at 10:01:17PM +0800, 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.
> > > > > 
> > > > > 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>
> > > > Is this just so we can drop the dependency on CONFIG_VIRTUALIZATION?
> > > > If yes what happens if we drop this patch?
> > > 
> > > The problem is that then VHOST_RING must depend on CONFIG_VIRTUALIZATION
> > > (which enable VHOST_IOTLB) to work.
> > > 
> > > But it looks to me CAIF and VOP doesn't requires CONFIG_VIRTUALIZATION.
> > How about stubs for IOTLB so VHOST_RING does not depend on VHOST_IOTLB?
> 
> 
> That could work.
> 
> 
> > I'm pretty sure neither user of vringh can actually use IOTLB, it's a
> > software only thing.
> 
> 
> Right.
> 
> 
> > 
> > > > Given the impact it had I'd like to defer it till next release if
> > > > possible.
> > > > 
> > > > 
> > > > > ---
> > > > >    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        | 23 ++++++++++++++---------
> > > > >    drivers/vhost/Kconfig.vringh |  6 ------
> > > > >    11 files changed, 16 insertions(+), 39 deletions(-)
> > > > >    delete mode 100644 drivers/vhost/Kconfig.vringh
> > > > > 
> > > > > diff --git a/arch/arm/kvm/Kconfig b/arch/arm/kvm/Kconfig
> > > > > index f591026347a5..be97393761bf 100644
> > > > > --- a/arch/arm/kvm/Kconfig
> > > > > +++ b/arch/arm/kvm/Kconfig
> > > > > @@ -54,6 +54,4 @@ config KVM_ARM_HOST
> > > > >    	---help---
> > > > >    	  Provides host support for ARM processors.
> > > > > -source "drivers/vhost/Kconfig"
> > > > > -
> > > > >    endif # VIRTUALIZATION
> > > > > diff --git a/arch/arm64/kvm/Kconfig b/arch/arm64/kvm/Kconfig
> > > > > index a475c68cbfec..449386d76441 100644
> > > > > --- a/arch/arm64/kvm/Kconfig
> > > > > +++ b/arch/arm64/kvm/Kconfig
> > > > > @@ -64,6 +64,4 @@ config KVM_ARM_PMU
> > > > >    config KVM_INDIRECT_VECTORS
> > > > >           def_bool KVM && (HARDEN_BRANCH_PREDICTOR || HARDEN_EL2_VECTORS)
> > > > > -source "drivers/vhost/Kconfig"
> > > > > -
> > > > >    endif # VIRTUALIZATION
> > > > > diff --git a/arch/mips/kvm/Kconfig b/arch/mips/kvm/Kconfig
> > > > > index eac25aef21e0..b91d145aa2d5 100644
> > > > > --- a/arch/mips/kvm/Kconfig
> > > > > +++ b/arch/mips/kvm/Kconfig
> > > > > @@ -72,6 +72,4 @@ config KVM_MIPS_DEBUG_COP0_COUNTERS
> > > > >    	  If unsure, say N.
> > > > > -source "drivers/vhost/Kconfig"
> > > > > -
> > > > >    endif # VIRTUALIZATION
> > > > > diff --git a/arch/powerpc/kvm/Kconfig b/arch/powerpc/kvm/Kconfig
> > > > > index 711fca9bc6f0..12885eda324e 100644
> > > > > --- a/arch/powerpc/kvm/Kconfig
> > > > > +++ b/arch/powerpc/kvm/Kconfig
> > > > > @@ -204,6 +204,4 @@ config KVM_XIVE
> > > > >    	default y
> > > > >    	depends on KVM_XICS && PPC_XIVE_NATIVE && KVM_BOOK3S_HV_POSSIBLE
> > > > > -source "drivers/vhost/Kconfig"
> > > > > -
> > > > >    endif # VIRTUALIZATION
> > > > > diff --git a/arch/s390/kvm/Kconfig b/arch/s390/kvm/Kconfig
> > > > > index d3db3d7ed077..def3b60f1fe8 100644
> > > > > --- a/arch/s390/kvm/Kconfig
> > > > > +++ b/arch/s390/kvm/Kconfig
> > > > > @@ -55,8 +55,4 @@ config KVM_S390_UCONTROL
> > > > >    	  If unsure, say N.
> > > > > -# OK, it's a little counter-intuitive to do this, but it puts it neatly under
> > > > > -# the virtualization menu.
> > > > > -source "drivers/vhost/Kconfig"
> > > > > -
> > > > >    endif # VIRTUALIZATION
> > > > > diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig
> > > > > index 991019d5eee1..0dfe70e17af9 100644
> > > > > --- a/arch/x86/kvm/Kconfig
> > > > > +++ b/arch/x86/kvm/Kconfig
> > > > > @@ -94,8 +94,4 @@ config KVM_MMU_AUDIT
> > > > >    	 This option adds a R/W kVM module parameter 'mmu_audit', which allows
> > > > >    	 auditing of KVM MMU events at runtime.
> > > > > -# OK, it's a little counter-intuitive to do this, but it puts it neatly under
> > > > > -# the virtualization menu.
> > > > > -source "drivers/vhost/Kconfig"
> > > > > -
> > > > >    endif # VIRTUALIZATION
> > > > > diff --git a/drivers/Kconfig b/drivers/Kconfig
> > > > > index 8befa53f43be..7a6d8b2b68b4 100644
> > > > > --- a/drivers/Kconfig
> > > > > +++ b/drivers/Kconfig
> > > > > @@ -138,6 +138,8 @@ source "drivers/virt/Kconfig"
> > > > >    source "drivers/virtio/Kconfig"
> > > > > +source "drivers/vhost/Kconfig"
> > > > > +
> > > > >    source "drivers/hv/Kconfig"
> > > > >    source "drivers/xen/Kconfig"
> > > > > diff --git a/drivers/misc/mic/Kconfig b/drivers/misc/mic/Kconfig
> > > > > index b6841ba6d922..8f201d019f5a 100644
> > > > > --- a/drivers/misc/mic/Kconfig
> > > > > +++ b/drivers/misc/mic/Kconfig
> > > > > @@ -133,8 +133,4 @@ config VOP
> > > > >    	  OS and tools for MIC to use with this driver are available from
> > > > >    	  <http://software.intel.com/en-us/mic-developer>.
> > > > > -if VOP
> > > > > -source "drivers/vhost/Kconfig.vringh"
> > > > > -endif
> > > > > -
> > > > >    endmenu
> > > > > diff --git a/drivers/net/caif/Kconfig b/drivers/net/caif/Kconfig
> > > > > index e74e2bb61236..9db0570c5beb 100644
> > > > > --- a/drivers/net/caif/Kconfig
> > > > > +++ b/drivers/net/caif/Kconfig
> > > > > @@ -58,8 +58,4 @@ config CAIF_VIRTIO
> > > > >    	---help---
> > > > >    	  The CAIF driver for CAIF over Virtio.
> > > > > -if CAIF_VIRTIO
> > > > > -source "drivers/vhost/Kconfig.vringh"
> > > > > -endif
> > > > > -
> > > > >    endif # CAIF_DRIVERS
> > > > > diff --git a/drivers/vhost/Kconfig b/drivers/vhost/Kconfig
> > > > > index 3d03ccbd1adc..4aef10a54cd1 100644
> > > > > --- a/drivers/vhost/Kconfig
> > > > > +++ b/drivers/vhost/Kconfig
> > > > > @@ -1,8 +1,20 @@
> > > > >    # 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.
> > > > > +
> > > > > +menuconfig VHOST
> > > > > +	tristate "Host kernel accelerator for virtio (VHOST)"
> > > > > +	help
> > > > > +	  This option is selected by any driver which needs to access
> > > > > +	  the core of vhost.
> > > > > +if VHOST
> > > > > +
> > > > The description here is wrong, isn't it?
> > > > VHOST and VHOST_RING are no longer selected, right?
> > > 
> > > For VHOST not currently.
> > Can we just bring it back and select it?
> 
> 
> Right, so if bring it back, we don't even need the stub.
> 
> How about something like attached?
> 
> Thanks
> 
> 
> > 
> > > For VHOST_RING, it was selected by CAIF, VOP and VDPASIM.
> > > 
> > > Thanks
> > > 
> > > 
> > > > 
> > > > >    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
> > > > > @@ -14,7 +26,6 @@ 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
> > > > > @@ -24,7 +35,6 @@ 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
> > > > > @@ -34,12 +44,6 @@ config VHOST_VSOCK
> > > > >    	To compile this driver as a module, choose M here: the module will be called
> > > > >    	vhost_vsock.
> > > > > -config VHOST
> > > > > -	tristate
> > > > > -	---help---
> > > > > -	  This option is selected by any driver which needs to access
> > > > > -	  the core of vhost.
> > > > > -
> > > > >    config VHOST_CROSS_ENDIAN_LEGACY
> > > > >    	bool "Cross-endian support for vhost"
> > > > >    	default n
> > > > > @@ -54,3 +58,4 @@ config VHOST_CROSS_ENDIAN_LEGACY
> > > > >    	  adds some overhead, it is disabled by default.
> > > > >    	  If unsure, say "N".
> > > > > +endif
> > > > > diff --git a/drivers/vhost/Kconfig.vringh b/drivers/vhost/Kconfig.vringh
> > > > > deleted file mode 100644
> > > > > index c1fe36a9b8d4..000000000000
> > > > > --- a/drivers/vhost/Kconfig.vringh
> > > > > +++ /dev/null
> > > > > @@ -1,6 +0,0 @@
> > > > > -# 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.
> > > > > -- 
> > > > > 2.20.1

> >From 9b3a5d23b8bf6b0a11e65e688335d782f8e6aa5c Mon Sep 17 00:00:00 2001
> From: Jason Wang <jasowang@redhat.com>
> Date: Wed, 1 Apr 2020 22:17:27 +0800
> Subject: [PATCH] vhost: let CONFIG_VHOST to be selected by drivers
> 
> The defconfig on some archs enable vhost_net or vhost_vsock by
> default. So instead of adding CONFIG_VHOST=m to all of those files,
> simply letting CONFIG_VHOST to be selected by all of the vhost
> drivers. This fixes the build on the archs with CONFIG_VHOST_NET=m in
> their defconfig.
> 
> Signed-off-by: Jason Wang <jasowang@redhat.com>
> ---
>  drivers/vhost/Kconfig | 15 +++++++++++----
>  1 file changed, 11 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/vhost/Kconfig b/drivers/vhost/Kconfig
> index 2523a1d4290a..362b832f5338 100644
> --- a/drivers/vhost/Kconfig
> +++ b/drivers/vhost/Kconfig
> @@ -11,19 +11,23 @@ config VHOST_RING
>  	  This option is selected by any driver which needs to access
>  	  the host side of a virtio ring.
>  
> -menuconfig VHOST
> -	tristate "Host kernel accelerator for virtio (VHOST)"
> -	depends on EVENTFD
> +config VHOST
> +	tristate
>  	select VHOST_IOTLB
>  	help
>  	  This option is selected by any driver which needs to access
>  	  the core of vhost.
>  
> -if VHOST
> +menuconfig VHOST_MENU
> +	bool "VHOST drivers"
> +	default y
> +
> +if VHOST_MENU

In fact this is similar to VIRTIO, and I wonder whether VIRTIO has also
been broken by
	commit 7b95fec6d2ffa53f4a8d637b0f223644d458ea4e
	Author: Vincent Legoll <vincent.legoll@gmail.com>
	Date:   Sun Jan 7 12:33:56 2018 +0100

	    virtio: make VIRTIO a menuconfig to ease disabling it all

I see lots of defconfigs set VIRTIO_PCI but not VIRTIO_MENU ...


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MST