Re: [PATCH] vfio: fix link failures when CONFIG_PCI_MSI is disabled

[Alex Williamson]

On Wed, 3 Feb 2016 20:51:08 +0000
Luis Henriques <luis.henriques@xxxxxxxxxxxxx> wrote:

> The following link failure occurs when CONFIG_PCI_MSI is not set:
> 
> drivers/built-in.o: In function `vfio_msi_set_vector_signal':
> :(.text+0x626640): undefined reference to `pci_write_msi_msg'
> 
> Signed-off-by: Luis Henriques <luis.henriques@xxxxxxxxxxxxx>
> ---
>  drivers/vfio/pci/Kconfig | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/vfio/pci/Kconfig b/drivers/vfio/pci/Kconfig
> index 02912f180c6d..b9dbfc9aeee1 100644
> --- a/drivers/vfio/pci/Kconfig
> +++ b/drivers/vfio/pci/Kconfig
> @@ -1,6 +1,6 @@
>  config VFIO_PCI
>  	tristate "VFIO support for PCI devices"
> -	depends on VFIO && PCI && EVENTFD
> +	depends on VFIO && PCI_MSI && EVENTFD
>  	select VFIO_VIRQFD
>  	select IRQ_BYPASS_MANAGER
>  	help
> 


It seems like a better solution would be to have pci stub these out
with static inlines when !CONFIG_PCI_MSI, we already do that for quite
a lot of MSI and MSI-X callbacks.  MSI/X on the device clearly won't
work if the host doesn't support MSI, and maybe there are improvements
to be made there, but MSI is a subcomponent of vfio-pci, the module
itself shouldn't depend on MSI.  Thanks,

Alex