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Subject: Re: [PATCH V9 1/9] vhost: refine vhost and vringh kconfig
To:     "Michael S. Tsirkin" <mst@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
References: <20200326140125.19794-1-jasowang@redhat.com>
 <20200326140125.19794-2-jasowang@redhat.com>
 <20200401092004-mutt-send-email-mst@kernel.org>
From:   Jason Wang <jasowang@redhat.com>
Message-ID: <6b4d169a-9962-6014-5423-1507059343e9@redhat.com>
Date:   Wed, 1 Apr 2020 22:08:59 +0800
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On 2020/4/1 =E4=B8=8B=E5=8D=889:22, 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=20
(which enable VHOST_IOTLB) to work.

But it looks to me CAIF and VOP doesn't requires CONFIG_VIRTUALIZATION.


> 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.
>>  =20
>> -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_VECTOR=
S)
>>  =20
>> -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
>>  =20
>>   	  If unsure, say N.
>>  =20
>> -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
>>  =20
>> -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
>>  =20
>>   	  If unsure, say N.
>>  =20
>> -# OK, it's a little counter-intuitive to do this, but it puts it neat=
ly 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 all=
ows
>>   	 auditing of KVM MMU events at runtime.
>>  =20
>> -# OK, it's a little counter-intuitive to do this, but it puts it neat=
ly 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"
>>  =20
>>   source "drivers/virtio/Kconfig"
>>  =20
>> +source "drivers/vhost/Kconfig"
>> +
>>   source "drivers/hv/Kconfig"
>>  =20
>>   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>.
>>  =20
>> -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.
>>  =20
>> -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.

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_V=
SOCK
>> @@ -34,12 +44,6 @@ config VHOST_VSOCK
>>   	To compile this driver as a module, choose M here: the module will =
be called
>>   	vhost_vsock.
>>  =20
>> -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.
>>  =20
>>   	  If unsure, say "N".
>> +endif
>> diff --git a/drivers/vhost/Kconfig.vringh b/drivers/vhost/Kconfig.vrin=
gh
>> 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.
>> --=20
>> 2.20.1