linux-kernel - Re: [PATCH v2 23/30] vfio/pci: re-introduce CONFIG_VFIO_PCI

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Date:   Tue, 18 Jan 2022 18:20:51 +0100
From:   Pierre Morel <pmorel@...ux.ibm.com>
To:     Matthew Rosato <mjrosato@...ux.ibm.com>, linux-s390@...r.kernel.org
Cc:     alex.williamson@...hat.com, cohuck@...hat.com,
        schnelle@...ux.ibm.com, farman@...ux.ibm.com,
        borntraeger@...ux.ibm.com, hca@...ux.ibm.com, gor@...ux.ibm.com,
        gerald.schaefer@...ux.ibm.com, agordeev@...ux.ibm.com,
        frankja@...ux.ibm.com, david@...hat.com, imbrenda@...ux.ibm.com,
        vneethv@...ux.ibm.com, oberpar@...ux.ibm.com, freude@...ux.ibm.com,
        thuth@...hat.com, pasic@...ux.ibm.com, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 23/30] vfio/pci: re-introduce CONFIG_VFIO_PCI_ZDEV



On 1/14/22 21:31, Matthew Rosato wrote:
> This was previously removed as unnecessary; while that was true, subsequent
> changes will make KVM an additional required component for vfio-pci-zdev.
> Let's re-introduce CONFIG_VFIO_PCI_ZDEV as now there is actually a reason
> to say 'n' for it (when not planning to CONFIG_KVM).
> 
> Signed-off-by: Matthew Rosato <mjrosato@...ux.ibm.com>
> ---
>   drivers/vfio/pci/Kconfig      | 11 +++++++++++
>   drivers/vfio/pci/Makefile     |  2 +-
>   include/linux/vfio_pci_core.h |  2 +-
>   3 files changed, 13 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/vfio/pci/Kconfig b/drivers/vfio/pci/Kconfig
> index 860424ccda1b..fedd1d4cb592 100644
> --- a/drivers/vfio/pci/Kconfig
> +++ b/drivers/vfio/pci/Kconfig
> @@ -42,5 +42,16 @@ config VFIO_PCI_IGD
>   	  and LPC bridge config space.
>   
>   	  To enable Intel IGD assignment through vfio-pci, say Y.
> +
> +config VFIO_PCI_ZDEV
> +	bool "VFIO PCI extensions for s390x KVM passthrough"
> +	depends on S390 && KVM
> +	default y
> +	help
> +	  Support s390x-specific extensions to enable support for enhancements
> +	  to KVM passthrough capabilities, such as interpretive execution of
> +	  zPCI instructions.
> +
> +	  To enable s390x KVM vfio-pci extensions, say Y.

In several patches we check on CONFIG_PCI (14,15,16,17 and 22) but we 
may have PCI without VFIO_PCI, wouldn't it be a problem?

Here we define a new CONFIG entry and I have two questions:

1- there is no dependency on VFIO_PCI while the functionality is 
obviously based on VFIO_PCI

2- Wouldn't it be possible to use this item and the single condition for 
the different checks we need through the new VFIO interpretation 
functionality.




>   endif
>   endif
> diff --git a/drivers/vfio/pci/Makefile b/drivers/vfio/pci/Makefile
> index 349d68d242b4..01b1f83d83d7 100644
> --- a/drivers/vfio/pci/Makefile
> +++ b/drivers/vfio/pci/Makefile
> @@ -1,7 +1,7 @@
>   # SPDX-License-Identifier: GPL-2.0-only
>   
>   vfio-pci-core-y := vfio_pci_core.o vfio_pci_intrs.o vfio_pci_rdwr.o vfio_pci_config.o
> -vfio-pci-core-$(CONFIG_S390) += vfio_pci_zdev.o
> +vfio-pci-core-$(CONFIG_VFIO_PCI_ZDEV) += vfio_pci_zdev.o
>   obj-$(CONFIG_VFIO_PCI_CORE) += vfio-pci-core.o
>   
>   vfio-pci-y := vfio_pci.o
> diff --git a/include/linux/vfio_pci_core.h b/include/linux/vfio_pci_core.h
> index ef9a44b6cf5d..5e2bca3b89db 100644
> --- a/include/linux/vfio_pci_core.h
> +++ b/include/linux/vfio_pci_core.h
> @@ -195,7 +195,7 @@ static inline int vfio_pci_igd_init(struct vfio_pci_core_device *vdev)
>   }
>   #endif
>   
> -#ifdef CONFIG_S390
> +#ifdef CONFIG_VFIO_PCI_ZDEV
>   extern int vfio_pci_info_zdev_add_caps(struct vfio_pci_core_device *vdev,
>   				       struct vfio_info_cap *caps);
>   #else
> 

-- 
Pierre Morel
IBM Lab Boeblingen