[PATCH v2 2/2] vhost: disable for OABI

[PATCH v2 2/2] vhost: disable for OABI

[Michael S. Tsirkin]

vhost is currently broken on the default ARM config.

The reason is that that uses apcs-gnu which is the ancient OABI that is been
deprecated for a long time.

Given that virtio support on such ancient systems is not needed in the
first place, let's just add something along the lines of

	depends on !ARM || AEABI

to the virtio Kconfig declaration, and add a comment that it has to do
with struct member alignment.

Note: we can't make VHOST and VHOST_RING themselves have
a dependency since these are selected. Add a new symbol for that.

Suggested-by: Ard Biesheuvel <ardb@kernel.org>
Siggested-by: Richard Earnshaw <Richard.Earnshaw@arm.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 drivers/misc/mic/Kconfig |  2 +-
 drivers/net/caif/Kconfig |  2 +-
 drivers/vdpa/Kconfig     |  2 +-
 drivers/vhost/Kconfig    | 17 +++++++++++++----
 4 files changed, 16 insertions(+), 7 deletions(-)

diff --git a/drivers/misc/mic/Kconfig b/drivers/misc/mic/Kconfig
index 8f201d019f5a..3bfe72c59864 100644
--- a/drivers/misc/mic/Kconfig
+++ b/drivers/misc/mic/Kconfig
@@ -116,7 +116,7 @@ config MIC_COSM
 
 config VOP
 	tristate "VOP Driver"
-	depends on VOP_BUS
+	depends on VOP_BUS && VHOST_DPN
 	select VHOST_RING
 	select VIRTIO
 	help
diff --git a/drivers/net/caif/Kconfig b/drivers/net/caif/Kconfig
index 9db0570c5beb..661c25eb1c46 100644
--- a/drivers/net/caif/Kconfig
+++ b/drivers/net/caif/Kconfig
@@ -50,7 +50,7 @@ config CAIF_HSI
 
 config CAIF_VIRTIO
 	tristate "CAIF virtio transport driver"
-	depends on CAIF && HAS_DMA
+	depends on CAIF && HAS_DMA && VHOST_DPN
 	select VHOST_RING
 	select VIRTIO
 	select GENERIC_ALLOCATOR
diff --git a/drivers/vdpa/Kconfig b/drivers/vdpa/Kconfig
index d0cb0e583a5d..aee28def466b 100644
--- a/drivers/vdpa/Kconfig
+++ b/drivers/vdpa/Kconfig
@@ -14,7 +14,7 @@ if VDPA_MENU
 
 config VDPA_SIM
 	tristate "vDPA device simulator"
-	depends on RUNTIME_TESTING_MENU && HAS_DMA
+	depends on RUNTIME_TESTING_MENU && HAS_DMA && VHOST_DPN
 	select VDPA
 	select VHOST_RING
 	select VHOST_IOTLB
diff --git a/drivers/vhost/Kconfig b/drivers/vhost/Kconfig
index cb6b17323eb2..b3486e218f62 100644
--- a/drivers/vhost/Kconfig
+++ b/drivers/vhost/Kconfig
@@ -12,6 +12,15 @@ config VHOST_RING
 	  This option is selected by any driver which needs to access
 	  the host side of a virtio ring.
 
+config VHOST_DPN
+	bool "VHOST dependencies"
+	depends on !ARM || AEABI
+	default y
+	help
+	  Anything selecting VHOST or VHOST_RING must depend on VHOST_DPN.
+	  This excludes the deprecated ARM ABI since that forces a 4 byte
+	  alignment on all structs - incompatible with virtio spec requirements.
+
 config VHOST
 	tristate
 	select VHOST_IOTLB
@@ -27,7 +36,7 @@ if VHOST_MENU
 
 config VHOST_NET
 	tristate "Host kernel accelerator for virtio net"
-	depends on NET && EVENTFD && (TUN || !TUN) && (TAP || !TAP)
+	depends on NET && EVENTFD && (TUN || !TUN) && (TAP || !TAP) && VHOST_DPN
 	select VHOST
 	---help---
 	  This kernel module can be loaded in host kernel to accelerate
@@ -39,7 +48,7 @@ config VHOST_NET
 
 config VHOST_SCSI
 	tristate "VHOST_SCSI TCM fabric driver"
-	depends on TARGET_CORE && EVENTFD
+	depends on TARGET_CORE && EVENTFD && VHOST_DPN
 	select VHOST
 	default n
 	---help---
@@ -48,7 +57,7 @@ config VHOST_SCSI
 
 config VHOST_VSOCK
 	tristate "vhost virtio-vsock driver"
-	depends on VSOCKETS && EVENTFD
+	depends on VSOCKETS && EVENTFD && VHOST_DPN
 	select VHOST
 	select VIRTIO_VSOCKETS_COMMON
 	default n
@@ -62,7 +71,7 @@ config VHOST_VSOCK
 
 config VHOST_VDPA
 	tristate "Vhost driver for vDPA-based backend"
-	depends on EVENTFD
+	depends on EVENTFD && VHOST_DPN
 	select VHOST
 	select VDPA
 	help
-- 
MST

Re: [PATCH v2 2/2] vhost: disable for OABI

[Ard Biesheuvel]

On Mon, 6 Apr 2020 at 14:12, Michael S. Tsirkin <mst@redhat.com> wrote:
>
> vhost is currently broken on the default ARM config.
>

Where did you get this idea? The report from the robot was using a
randconfig build, and in general, AEABI is required to run anything on
any modern ARM system .


> The reason is that that uses apcs-gnu which is the ancient OABI that is been
> deprecated for a long time.
>
> Given that virtio support on such ancient systems is not needed in the
> first place, let's just add something along the lines of
>
>         depends on !ARM || AEABI
>
> to the virtio Kconfig declaration, and add a comment that it has to do
> with struct member alignment.
>
> Note: we can't make VHOST and VHOST_RING themselves have
> a dependency since these are selected. Add a new symbol for that.
>
> Suggested-by: Ard Biesheuvel <ardb@kernel.org>
> Siggested-by: Richard Earnshaw <Richard.Earnshaw@arm.com>

typo ^^^


> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> ---
>  drivers/misc/mic/Kconfig |  2 +-
>  drivers/net/caif/Kconfig |  2 +-
>  drivers/vdpa/Kconfig     |  2 +-
>  drivers/vhost/Kconfig    | 17 +++++++++++++----
>  4 files changed, 16 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/misc/mic/Kconfig b/drivers/misc/mic/Kconfig
> index 8f201d019f5a..3bfe72c59864 100644
> --- a/drivers/misc/mic/Kconfig
> +++ b/drivers/misc/mic/Kconfig
> @@ -116,7 +116,7 @@ config MIC_COSM
>
>  config VOP
>         tristate "VOP Driver"
> -       depends on VOP_BUS
> +       depends on VOP_BUS && VHOST_DPN
>         select VHOST_RING
>         select VIRTIO
>         help
> diff --git a/drivers/net/caif/Kconfig b/drivers/net/caif/Kconfig
> index 9db0570c5beb..661c25eb1c46 100644
> --- a/drivers/net/caif/Kconfig
> +++ b/drivers/net/caif/Kconfig
> @@ -50,7 +50,7 @@ config CAIF_HSI
>
>  config CAIF_VIRTIO
>         tristate "CAIF virtio transport driver"
> -       depends on CAIF && HAS_DMA
> +       depends on CAIF && HAS_DMA && VHOST_DPN
>         select VHOST_RING
>         select VIRTIO
>         select GENERIC_ALLOCATOR
> diff --git a/drivers/vdpa/Kconfig b/drivers/vdpa/Kconfig
> index d0cb0e583a5d..aee28def466b 100644
> --- a/drivers/vdpa/Kconfig
> +++ b/drivers/vdpa/Kconfig
> @@ -14,7 +14,7 @@ if VDPA_MENU
>
>  config VDPA_SIM
>         tristate "vDPA device simulator"
> -       depends on RUNTIME_TESTING_MENU && HAS_DMA
> +       depends on RUNTIME_TESTING_MENU && HAS_DMA && VHOST_DPN
>         select VDPA
>         select VHOST_RING
>         select VHOST_IOTLB
> diff --git a/drivers/vhost/Kconfig b/drivers/vhost/Kconfig
> index cb6b17323eb2..b3486e218f62 100644
> --- a/drivers/vhost/Kconfig
> +++ b/drivers/vhost/Kconfig
> @@ -12,6 +12,15 @@ config VHOST_RING
>           This option is selected by any driver which needs to access
>           the host side of a virtio ring.
>
> +config VHOST_DPN
> +       bool "VHOST dependencies"
> +       depends on !ARM || AEABI
> +       default y
> +       help
> +         Anything selecting VHOST or VHOST_RING must depend on VHOST_DPN.
> +         This excludes the deprecated ARM ABI since that forces a 4 byte
> +         alignment on all structs - incompatible with virtio spec requirements.
> +
>  config VHOST
>         tristate
>         select VHOST_IOTLB
> @@ -27,7 +36,7 @@ if VHOST_MENU
>
>  config VHOST_NET
>         tristate "Host kernel accelerator for virtio net"
> -       depends on NET && EVENTFD && (TUN || !TUN) && (TAP || !TAP)
> +       depends on NET && EVENTFD && (TUN || !TUN) && (TAP || !TAP) && VHOST_DPN
>         select VHOST
>         ---help---
>           This kernel module can be loaded in host kernel to accelerate
> @@ -39,7 +48,7 @@ config VHOST_NET
>
>  config VHOST_SCSI
>         tristate "VHOST_SCSI TCM fabric driver"
> -       depends on TARGET_CORE && EVENTFD
> +       depends on TARGET_CORE && EVENTFD && VHOST_DPN
>         select VHOST
>         default n
>         ---help---
> @@ -48,7 +57,7 @@ config VHOST_SCSI
>
>  config VHOST_VSOCK
>         tristate "vhost virtio-vsock driver"
> -       depends on VSOCKETS && EVENTFD
> +       depends on VSOCKETS && EVENTFD && VHOST_DPN
>         select VHOST
>         select VIRTIO_VSOCKETS_COMMON
>         default n
> @@ -62,7 +71,7 @@ config VHOST_VSOCK
>
>  config VHOST_VDPA
>         tristate "Vhost driver for vDPA-based backend"
> -       depends on EVENTFD
> +       depends on EVENTFD && VHOST_DPN
>         select VHOST
>         select VDPA
>         help
> --
> MST
>

Re: [PATCH v2 2/2] vhost: disable for OABI

[Arnd Bergmann]

On Mon, Apr 6, 2020 at 2:12 PM Michael S. Tsirkin <mst@redhat.com> wrote:

>
> +config VHOST_DPN
> +       bool "VHOST dependencies"
> +       depends on !ARM || AEABI
> +       default y
> +       help
> +         Anything selecting VHOST or VHOST_RING must depend on VHOST_DPN.
> +         This excludes the deprecated ARM ABI since that forces a 4 byte
> +         alignment on all structs - incompatible with virtio spec requirements.
> +

This should not be a user-visible option, so just make this 'def_bool
!ARM || AEABI'

      Arnd

Re: [PATCH v2 2/2] vhost: disable for OABI

[Michael S. Tsirkin]

On Mon, Apr 06, 2020 at 02:45:13PM +0200, Ard Biesheuvel wrote:
> On Mon, 6 Apr 2020 at 14:12, Michael S. Tsirkin <mst@redhat.com> wrote:
> >
> > vhost is currently broken on the default ARM config.
> >
> 
> Where did you get this idea? The report from the robot was using a
> randconfig build, and in general, AEABI is required to run anything on
> any modern ARM system .

Oh - I forgot it's randconfig. This part is wrong, sorry.
I decided to just force 2-byte alignment
instead (seems more robust) but I'll take this into account
if we do decide to add this dependency.


> 
> > The reason is that that uses apcs-gnu which is the ancient OABI that is been
> > deprecated for a long time.
> >
> > Given that virtio support on such ancient systems is not needed in the
> > first place, let's just add something along the lines of
> >
> >         depends on !ARM || AEABI
> >
> > to the virtio Kconfig declaration, and add a comment that it has to do
> > with struct member alignment.
> >
> > Note: we can't make VHOST and VHOST_RING themselves have
> > a dependency since these are selected. Add a new symbol for that.
> >
> > Suggested-by: Ard Biesheuvel <ardb@kernel.org>
> > Siggested-by: Richard Earnshaw <Richard.Earnshaw@arm.com>
> 
> typo ^^^


Thanks!

> 
> > Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> > ---
> >  drivers/misc/mic/Kconfig |  2 +-
> >  drivers/net/caif/Kconfig |  2 +-
> >  drivers/vdpa/Kconfig     |  2 +-
> >  drivers/vhost/Kconfig    | 17 +++++++++++++----
> >  4 files changed, 16 insertions(+), 7 deletions(-)
> >
> > diff --git a/drivers/misc/mic/Kconfig b/drivers/misc/mic/Kconfig
> > index 8f201d019f5a..3bfe72c59864 100644
> > --- a/drivers/misc/mic/Kconfig
> > +++ b/drivers/misc/mic/Kconfig
> > @@ -116,7 +116,7 @@ config MIC_COSM
> >
> >  config VOP
> >         tristate "VOP Driver"
> > -       depends on VOP_BUS
> > +       depends on VOP_BUS && VHOST_DPN
> >         select VHOST_RING
> >         select VIRTIO
> >         help
> > diff --git a/drivers/net/caif/Kconfig b/drivers/net/caif/Kconfig
> > index 9db0570c5beb..661c25eb1c46 100644
> > --- a/drivers/net/caif/Kconfig
> > +++ b/drivers/net/caif/Kconfig
> > @@ -50,7 +50,7 @@ config CAIF_HSI
> >
> >  config CAIF_VIRTIO
> >         tristate "CAIF virtio transport driver"
> > -       depends on CAIF && HAS_DMA
> > +       depends on CAIF && HAS_DMA && VHOST_DPN
> >         select VHOST_RING
> >         select VIRTIO
> >         select GENERIC_ALLOCATOR
> > diff --git a/drivers/vdpa/Kconfig b/drivers/vdpa/Kconfig
> > index d0cb0e583a5d..aee28def466b 100644
> > --- a/drivers/vdpa/Kconfig
> > +++ b/drivers/vdpa/Kconfig
> > @@ -14,7 +14,7 @@ if VDPA_MENU
> >
> >  config VDPA_SIM
> >         tristate "vDPA device simulator"
> > -       depends on RUNTIME_TESTING_MENU && HAS_DMA
> > +       depends on RUNTIME_TESTING_MENU && HAS_DMA && VHOST_DPN
> >         select VDPA
> >         select VHOST_RING
> >         select VHOST_IOTLB
> > diff --git a/drivers/vhost/Kconfig b/drivers/vhost/Kconfig
> > index cb6b17323eb2..b3486e218f62 100644
> > --- a/drivers/vhost/Kconfig
> > +++ b/drivers/vhost/Kconfig
> > @@ -12,6 +12,15 @@ config VHOST_RING
> >           This option is selected by any driver which needs to access
> >           the host side of a virtio ring.
> >
> > +config VHOST_DPN
> > +       bool "VHOST dependencies"
> > +       depends on !ARM || AEABI
> > +       default y
> > +       help
> > +         Anything selecting VHOST or VHOST_RING must depend on VHOST_DPN.
> > +         This excludes the deprecated ARM ABI since that forces a 4 byte
> > +         alignment on all structs - incompatible with virtio spec requirements.
> > +
> >  config VHOST
> >         tristate
> >         select VHOST_IOTLB
> > @@ -27,7 +36,7 @@ if VHOST_MENU
> >
> >  config VHOST_NET
> >         tristate "Host kernel accelerator for virtio net"
> > -       depends on NET && EVENTFD && (TUN || !TUN) && (TAP || !TAP)
> > +       depends on NET && EVENTFD && (TUN || !TUN) && (TAP || !TAP) && VHOST_DPN
> >         select VHOST
> >         ---help---
> >           This kernel module can be loaded in host kernel to accelerate
> > @@ -39,7 +48,7 @@ config VHOST_NET
> >
> >  config VHOST_SCSI
> >         tristate "VHOST_SCSI TCM fabric driver"
> > -       depends on TARGET_CORE && EVENTFD
> > +       depends on TARGET_CORE && EVENTFD && VHOST_DPN
> >         select VHOST
> >         default n
> >         ---help---
> > @@ -48,7 +57,7 @@ config VHOST_SCSI
> >
> >  config VHOST_VSOCK
> >         tristate "vhost virtio-vsock driver"
> > -       depends on VSOCKETS && EVENTFD
> > +       depends on VSOCKETS && EVENTFD && VHOST_DPN
> >         select VHOST
> >         select VIRTIO_VSOCKETS_COMMON
> >         default n
> > @@ -62,7 +71,7 @@ config VHOST_VSOCK
> >
> >  config VHOST_VDPA
> >         tristate "Vhost driver for vDPA-based backend"
> > -       depends on EVENTFD
> > +       depends on EVENTFD && VHOST_DPN
> >         select VHOST
> >         select VDPA
> >         help
> > --
> > MST
> >

Re: [PATCH v2 2/2] vhost: disable for OABI

[Michael S. Tsirkin]

On Mon, Apr 06, 2020 at 02:50:32PM +0200, Arnd Bergmann wrote:
> On Mon, Apr 6, 2020 at 2:12 PM Michael S. Tsirkin <mst@redhat.com> wrote:
> 
> >
> > +config VHOST_DPN
> > +       bool "VHOST dependencies"
> > +       depends on !ARM || AEABI
> > +       default y
> > +       help
> > +         Anything selecting VHOST or VHOST_RING must depend on VHOST_DPN.
> > +         This excludes the deprecated ARM ABI since that forces a 4 byte
> > +         alignment on all structs - incompatible with virtio spec requirements.
> > +
> 
> This should not be a user-visible option, so just make this 'def_bool
> !ARM || AEABI'
> 
>       Arnd

I like keeping some kind of hint around for when one tries to understand
why is a specific symbol visible.

-- 
MST

Re: [PATCH v2 2/2] vhost: disable for OABI

[Arnd Bergmann]

On Mon, Apr 6, 2020 at 3:02 PM Michael S. Tsirkin <mst@redhat.com> wrote:
>
> On Mon, Apr 06, 2020 at 02:50:32PM +0200, Arnd Bergmann wrote:
> > On Mon, Apr 6, 2020 at 2:12 PM Michael S. Tsirkin <mst@redhat.com> wrote:
> >
> > >
> > > +config VHOST_DPN
> > > +       bool "VHOST dependencies"
> > > +       depends on !ARM || AEABI
> > > +       default y
> > > +       help
> > > +         Anything selecting VHOST or VHOST_RING must depend on VHOST_DPN.
> > > +         This excludes the deprecated ARM ABI since that forces a 4 byte
> > > +         alignment on all structs - incompatible with virtio spec requirements.
> > > +
> >
> > This should not be a user-visible option, so just make this 'def_bool
> > !ARM || AEABI'
> >
>
> I like keeping some kind of hint around for when one tries to understand
> why is a specific symbol visible.

I meant you should remove the "VHOST dependencies" prompt, not the
help text, which is certainly useful here. You can also use the three lines

     bool
     depends on !ARM || AEABI
     default y

in front of the help text, but those are equivalent to the one-line version
I suggested.

     Arnd

Re: [PATCH v2 2/2] vhost: disable for OABI

[Michael S. Tsirkin]

On Mon, Apr 06, 2020 at 03:15:20PM +0200, Arnd Bergmann wrote:
> On Mon, Apr 6, 2020 at 3:02 PM Michael S. Tsirkin <mst@redhat.com> wrote:
> >
> > On Mon, Apr 06, 2020 at 02:50:32PM +0200, Arnd Bergmann wrote:
> > > On Mon, Apr 6, 2020 at 2:12 PM Michael S. Tsirkin <mst@redhat.com> wrote:
> > >
> > > >
> > > > +config VHOST_DPN
> > > > +       bool "VHOST dependencies"
> > > > +       depends on !ARM || AEABI
> > > > +       default y
> > > > +       help
> > > > +         Anything selecting VHOST or VHOST_RING must depend on VHOST_DPN.
> > > > +         This excludes the deprecated ARM ABI since that forces a 4 byte
> > > > +         alignment on all structs - incompatible with virtio spec requirements.
> > > > +
> > >
> > > This should not be a user-visible option, so just make this 'def_bool
> > > !ARM || AEABI'
> > >
> >
> > I like keeping some kind of hint around for when one tries to understand
> > why is a specific symbol visible.
> 
> I meant you should remove the "VHOST dependencies" prompt, not the
> help text, which is certainly useful here. You can also use the three lines
> 
>      bool
>      depends on !ARM || AEABI
>      default y
> 
> in front of the help text, but those are equivalent to the one-line version
> I suggested.
> 
>      Arnd

Oh right. Good point. Thanks!

-- 
MST