Re: [PATCH rc] kvm: Prevent compiling virt/kvm/vfio.c unless VFIO is selected

[Michael Ellerman <mpe@ellerman.id.au>]

Jason Gunthorpe <jgg@nvidia.com> writes:
> There are a bunch of reported randconfig failures now because of this,
> something like:
>
>>> arch/powerpc/kvm/../../../virt/kvm/vfio.c:89:7: warning: attribute declaration must precede definition [-Wignored-attributes]
>            fn = symbol_get(vfio_file_iommu_group);
>                 ^
>    include/linux/module.h:805:60: note: expanded from macro 'symbol_get'
>    #define symbol_get(x) ({ extern typeof(x) x __attribute__((weak,visibility("hidden"))); &(x); })
>
> It happens because the arch forces KVM_VFIO without knowing if VFIO is
> even enabled.
>
> Split the kconfig so the arch selects the usual HAVE_KVM_ARCH_VFIO and
> then KVM_VFIO is only enabled if the arch wants it and VFIO is turned on.
>
> Reported-by: kernel test robot <lkp@intel.com>
> Closes: https://lore.kernel.org/oe-kbuild-all/202308251949.5IiaV0sz-lkp@intel.com/
> Closes: https://lore.kernel.org/oe-kbuild-all/202309030741.82aLACDG-lkp@intel.com/
> Closes: https://lore.kernel.org/oe-kbuild-all/202309110914.QLH0LU6L-lkp@intel.com/
> Cc: Nick Desaulniers <ndesaulniers@google.com>
> Fixes: c1cce6d079b8 ("vfio: Compile vfio_group infrastructure optionally")
> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
> ---
>  arch/arm64/kvm/Kconfig   | 2 +-
>  arch/powerpc/kvm/Kconfig | 2 +-
>  arch/s390/kvm/Kconfig    | 2 +-
>  arch/x86/kvm/Kconfig     | 2 +-
>  virt/kvm/Kconfig         | 7 ++++++-
>  5 files changed, 10 insertions(+), 5 deletions(-)
>
> Sean's large series will also address this:
>
> https://lore.kernel.org/kvm/20230916003118.2540661-7-seanjc@google.com/
>
> I don't know if it is sever enough to fix in the rc cycle, but here is the
> patch.

Thanks for debugging this, I had seen it but hadn't got around to it.

I think it's definitely worth fixing now. It's a pretty simple patch and
it's still early in the rc cycle.

Tested-by: Michael Ellerman <mpe@ellerman.id.au>

cheers

> diff --git a/arch/arm64/kvm/Kconfig b/arch/arm64/kvm/Kconfig
> index 83c1e09be42e5b..7c43eaea51ce05 100644
> --- a/arch/arm64/kvm/Kconfig
> +++ b/arch/arm64/kvm/Kconfig
> @@ -28,7 +28,7 @@ menuconfig KVM
>  	select KVM_MMIO
>  	select KVM_GENERIC_DIRTYLOG_READ_PROTECT
>  	select KVM_XFER_TO_GUEST_WORK
> -	select KVM_VFIO
> +	select HAVE_KVM_ARCH_VFIO
>  	select HAVE_KVM_EVENTFD
>  	select HAVE_KVM_IRQFD
>  	select HAVE_KVM_DIRTY_RING_ACQ_REL
> diff --git a/arch/powerpc/kvm/Kconfig b/arch/powerpc/kvm/Kconfig
> index 902611954200df..b64824e4cbc1eb 100644
> --- a/arch/powerpc/kvm/Kconfig
> +++ b/arch/powerpc/kvm/Kconfig
> @@ -22,7 +22,7 @@ config KVM
>  	select PREEMPT_NOTIFIERS
>  	select HAVE_KVM_EVENTFD
>  	select HAVE_KVM_VCPU_ASYNC_IOCTL
> -	select KVM_VFIO
> +	select HAVE_KVM_ARCH_VFIO
>  	select IRQ_BYPASS_MANAGER
>  	select HAVE_KVM_IRQ_BYPASS
>  	select INTERVAL_TREE
> diff --git a/arch/s390/kvm/Kconfig b/arch/s390/kvm/Kconfig
> index 45fdf2a9b2e326..d206ad3a777d5d 100644
> --- a/arch/s390/kvm/Kconfig
> +++ b/arch/s390/kvm/Kconfig
> @@ -31,7 +31,7 @@ config KVM
>  	select HAVE_KVM_IRQ_ROUTING
>  	select HAVE_KVM_INVALID_WAKEUPS
>  	select HAVE_KVM_NO_POLL
> -	select KVM_VFIO
> +	select HAVE_KVM_ARCH_VFIO
>  	select INTERVAL_TREE
>  	select MMU_NOTIFIER
>  	help
> diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig
> index ed90f148140dfe..8e70e693f90e30 100644
> --- a/arch/x86/kvm/Kconfig
> +++ b/arch/x86/kvm/Kconfig
> @@ -45,7 +45,7 @@ config KVM
>  	select HAVE_KVM_NO_POLL
>  	select KVM_XFER_TO_GUEST_WORK
>  	select KVM_GENERIC_DIRTYLOG_READ_PROTECT
> -	select KVM_VFIO
> +	select HAVE_KVM_ARCH_VFIO
>  	select INTERVAL_TREE
>  	select HAVE_KVM_PM_NOTIFIER if PM
>  	select KVM_GENERIC_HARDWARE_ENABLING
> diff --git a/virt/kvm/Kconfig b/virt/kvm/Kconfig
> index 484d0873061ca5..0bf34809e1bbfe 100644
> --- a/virt/kvm/Kconfig
> +++ b/virt/kvm/Kconfig
> @@ -59,9 +59,14 @@ config HAVE_KVM_MSI
>  config HAVE_KVM_CPU_RELAX_INTERCEPT
>         bool
>  
> -config KVM_VFIO
> +config HAVE_KVM_ARCH_VFIO
>         bool
>  
> +config KVM_VFIO
> +       def_bool y
> +       depends on HAVE_KVM_ARCH_VFIO
> +       depends on VFIO
> +
>  config HAVE_KVM_INVALID_WAKEUPS
>         bool
>  
>
> base-commit: 0bb80ecc33a8fb5a682236443c1e740d5c917d1d
> -- 
> 2.42.0