linux-kernel - RE: [PATCH] cdx: Fix missing GENERIC_MSI

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Message-ID:
 <BL1PR12MB5333449243C7FE258728C8E39D5EA@BL1PR12MB5333.namprd12.prod.outlook.com>
Date: Thu, 24 Jul 2025 07:29:48 +0000
From: "Agarwal, Nikhil" <nikhil.agarwal@....com>
To: Alex Williamson <alex.williamson@...hat.com>, Krzysztof Kozlowski
	<krzysztof.kozlowski@...aro.org>
CC: "Gupta, Nipun" <Nipun.Gupta@....com>, Greg Kroah-Hartman
	<gregkh@...uxfoundation.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, Randy Dunlap <rdunlap@...radead.org>
Subject: RE: [PATCH] cdx: Fix missing GENERIC_MSI_IRQ on compile test



> -----Original Message-----
> From: Alex Williamson <alex.williamson@...hat.com>
> Sent: Friday, July 18, 2025 2:11 AM
> To: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
> Cc: Gupta, Nipun <Nipun.Gupta@....com>; Agarwal, Nikhil
> <nikhil.agarwal@....com>; Greg Kroah-Hartman <gregkh@...uxfoundation.org>;
> linux-kernel@...r.kernel.org; Randy Dunlap <rdunlap@...radead.org>
> Subject: Re: [PATCH] cdx: Fix missing GENERIC_MSI_IRQ on compile test
> 
> On Thu, 17 Jul 2025 13:33:58 -0600
> Alex Williamson <alex.williamson@...hat.com> wrote:
> 
> > On Wed, 16 Jul 2025 08:49:04 +0200
> > Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org> wrote:
> >
> > > CDX_BUS driver uses msi_setup_device_data() which is selected by
> > > GENERIC_MSI_IRQ, thus compile testing without the latter failed:
> > >
> > >   /usr/bin/ld: drivers/cdx/cdx.o: in function `cdx_probe':
> > >   build/drivers/cdx/cdx.c:314: undefined reference to `msi_setup_device_data'
> > >
> > > Reported-by: Randy Dunlap <rdunlap@...radead.org>
> > > Closes:
> > > https://lore.kernel.org/all/b2c54a12-480c-448a-8b90-333cb03d9c14@inf
> > > radead.org/
> > > Fixes: 7f81907b7e3f ("cdx: Enable compile testing")
> > > Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
> > > ---
> > >  drivers/cdx/Kconfig | 1 +
> > >  1 file changed, 1 insertion(+)
> > >
> > > diff --git a/drivers/cdx/Kconfig b/drivers/cdx/Kconfig index
> > > 1f1e360507d7..3af41f51cf38 100644
> > > --- a/drivers/cdx/Kconfig
> > > +++ b/drivers/cdx/Kconfig
> > > @@ -8,6 +8,7 @@
> > >  config CDX_BUS
> > >  	bool "CDX Bus driver"
> > >  	depends on OF && ARM64 || COMPILE_TEST
> > > +	select GENERIC_MSI_IRQ
> > >  	help
> > >  	  Driver to enable Composable DMA Transfer(CDX) Bus. CDX bus
> > >  	  exposes Fabric devices which uses composable DMA IP to the
> >
> > This looks incomplete to me.  The Makefile has:
> >
> > ifdef CONFIG_GENERIC_MSI_IRQ
> > obj-$(CONFIG_CDX_BUS) += cdx_msi.o
> > endif
> >
> > The call to msi_setup_device_data(), the conditional inclusion of
> > cdx_msi.o, and cdx_msi.c itself were added in 0e439ba38e61 ("cdx: add
> > MSI support for CDX bus").  That's the source of the issue, not the
> > Kconfig update to build under COMPILE_TEST, but also the Makefile
> > should be updated to statically include cdx_msi.o.  Thanks,
> 
> Also, we may not be philosophically aligned on this, but if CDX_BUS selects
> GENERIC_MSI_IRQ and CDX_CONTROLLER depends on CDX_BUS, then the
> select of the same under CDX_CONTROLLER becomes redundant.
> 
> Independent of that there are also some ifdefs in cdx_bus.h that would become
> invalid if the entire CDX_BUS depends on GENERIC_MSI_IRQ.  It really kinda
> looks like CDX_BUS expects a use case that doesn't depend on
> GENERIC_MSI_IRQ and I wonder if the right answer isn't just:
> 
> diff --git a/drivers/cdx/cdx.c b/drivers/cdx/cdx.c index 092306ca2541..3d50f8cd9c0b
> 100644
> --- a/drivers/cdx/cdx.c
> +++ b/drivers/cdx/cdx.c
> @@ -310,7 +310,7 @@ static int cdx_probe(struct device *dev)
>  	 * Setup MSI device data so that generic MSI alloc/free can
>  	 * be used by the device driver.
>  	 */
> -	if (cdx->msi_domain) {
> +	if (IS_ENABLED(CONFIG_GENERIC_MSI_IRQ) && cdx->msi_domain) {
>  		error = msi_setup_device_data(&cdx_dev->dev);
>  		if (error)
>  			return error;
> @@ -833,7 +833,7 @@ int cdx_device_add(struct cdx_dev_params *dev_params)
>  		     ((cdx->id << CDX_CONTROLLER_ID_SHIFT) | (cdx_dev-
> >bus_num & CDX_BUS_NUM_MASK)),
>  		     cdx_dev->dev_num);
> 
> -	if (cdx->msi_domain) {
> +	if (IS_ENABLED(CONFIG_GENERIC_MSI_IRQ) && cdx->msi_domain) {
>  		cdx_dev->num_msi = dev_params->num_msi;
>  		dev_set_msi_domain(&cdx_dev->dev, cdx->msi_domain);
>  	}
> 
> Then I suppose vfio-cdx would also have the option to either select/depend on
> GENERIC_MSI_IRQ or perhaps get away with stubbing vfio_cdx_set_irqs_ioctl and
> vfio_cdx_irqs_cleanup and conditionally building intr.o, depending on if there's a
> use case without MSI.
Apologies for the late response here, was on vacation last week. CDX bus is supposed to be independent of CONFIG_GENERIC_MSI_IRQ.
Will send a patch to fix it on similar lines suggested by Alex.

> Thanks,
> 
> Alex