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

From: Michael S. Tsirkin
Date: Wed Apr 01 2020 - 10:35:15 EST

On Wed, Apr 01, 2020 at 10:29:32PM +0800, Jason Wang wrote:
>
> On 2020/4/1 äå10:13, Michael S. Tsirkin wrote:
> > On Wed, Apr 01, 2020 at 10:08:59PM +0800, Jason Wang wrote:
> > > On 2020/4/1 äå9:22, 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@xxxxxxxxxx>
> > > > 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@xxxxxxxxxx>
> 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@xxxxxxxxxx>
> ---
> 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

Will this not still have the problem with defconfigs? They don't set
VHOST_MENU ...

>
> 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 +39,7 @@ 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
> @@ -43,6 +48,7 @@ config VHOST_SCSI
> config VHOST_VSOCK
> tristate "vhost virtio-vsock driver"
> depends on VSOCKETS && EVENTFD
> + select VHOST
> select VIRTIO_VSOCKETS_COMMON
> default n
> ---help---
> @@ -56,6 +62,7 @@ config VHOST_VSOCK
> config VHOST_VDPA
> tristate "Vhost driver for vDPA-based backend"
> depends on EVENTFD
> + select VHOST
> select VDPA
> help
> This kernel module can be loaded in host kernel to accelerate
> --
> 2.20.1
>