Re: [PATCH v1 2/4] xen/pci: Introduce new CONFIG_HAS_PCI_ATS flag for PCI ATS functionality.

[Stefano Stabellini <sstabellini@kernel.org>]

On Mon, 26 Oct 2020, Rahul Singh wrote:
> PCI ATS functionality is not enabled and tested for ARM architecture
> but it is enabled for x86 and referenced in common passthrough/pci.c
> code.
> 
> Therefore introducing the new flag to enable the ATS functionality for
> x86 only to avoid issues for ARM architecture.
> 
> No functional change.
> 
> Signed-off-by: Rahul Singh <rahul.singh@arm.com>
> ---
>  xen/arch/x86/Kconfig                     |  1 +
>  xen/drivers/passthrough/ats.h            | 24 ++++++++++++++++++++++++
>  xen/drivers/passthrough/vtd/x86/Makefile |  2 +-
>  xen/drivers/passthrough/x86/Makefile     |  2 +-
>  xen/drivers/pci/Kconfig                  |  3 +++
>  5 files changed, 30 insertions(+), 2 deletions(-)
> 
> diff --git a/xen/arch/x86/Kconfig b/xen/arch/x86/Kconfig
> index 24868aa6ad..31906e9c97 100644
> --- a/xen/arch/x86/Kconfig
> +++ b/xen/arch/x86/Kconfig
> @@ -20,6 +20,7 @@ config X86
>  	select HAS_NS16550
>  	select HAS_PASSTHROUGH
>  	select HAS_PCI
> +	select HAS_PCI_ATS
>  	select HAS_PDX
>  	select HAS_SCHED_GRANULARITY
>  	select HAS_UBSAN
> diff --git a/xen/drivers/passthrough/ats.h b/xen/drivers/passthrough/ats.h
> index 22ae209b37..a0af07b287 100644
> --- a/xen/drivers/passthrough/ats.h
> +++ b/xen/drivers/passthrough/ats.h
> @@ -17,6 +17,8 @@
>  
>  #include <xen/pci_regs.h>
>  
> +#ifdef CONFIG_HAS_PCI_ATS
> +
>  #define ATS_REG_CAP    4
>  #define ATS_REG_CTL    6
>  #define ATS_QUEUE_DEPTH_MASK     0x1f
> @@ -48,5 +50,27 @@ static inline int pci_ats_device(int seg, int bus, int devfn)
>      return pci_find_ext_capability(seg, bus, devfn, PCI_EXT_CAP_ID_ATS);
>  }
>  
> +#else
> +
> +static inline int enable_ats_device(struct pci_dev *pdev,
> +                                    struct list_head *ats_list)
> +{
> +    return -ENODEV;
> +}
> +
> +static inline void disable_ats_device(struct pci_dev *pdev) { }
> +
> +static inline int pci_ats_enabled(int seg, int bus, int devfn)
> +{
> +    return -ENODEV;
> +}

pci_ats_enabled returns 0 when ATS is not enabled


> +static inline int pci_ats_device(int seg, int bus, int devfn)
> +{
> +    return -ENODEV;

also returns 0 when ATS is not enabled


> +}
> +
> +#endif /* CONFIG_HAS_PCI_ATS */
> +
>  #endif /* _ATS_H_ */
>  
> diff --git a/xen/drivers/passthrough/vtd/x86/Makefile b/xen/drivers/passthrough/vtd/x86/Makefile
> index 4ef00a4c5b..60f79fe263 100644
> --- a/xen/drivers/passthrough/vtd/x86/Makefile
> +++ b/xen/drivers/passthrough/vtd/x86/Makefile
> @@ -1,3 +1,3 @@
> -obj-y += ats.o
> +obj-$(CONFIG_HAS_PCI_ATS) += ats.o
>  obj-$(CONFIG_HVM) += hvm.o
>  obj-y += vtd.o
> diff --git a/xen/drivers/passthrough/x86/Makefile b/xen/drivers/passthrough/x86/Makefile
> index a70cf9460d..05e6f51f25 100644
> --- a/xen/drivers/passthrough/x86/Makefile
> +++ b/xen/drivers/passthrough/x86/Makefile
> @@ -1,2 +1,2 @@
> -obj-y += ats.o
> +obj-$(CONFIG_HAS_PCI_ATS) += ats.o
>  obj-y += iommu.o
> diff --git a/xen/drivers/pci/Kconfig b/xen/drivers/pci/Kconfig
> index 7da03fa13b..1588d4a91e 100644
> --- a/xen/drivers/pci/Kconfig
> +++ b/xen/drivers/pci/Kconfig
> @@ -1,3 +1,6 @@
>  
>  config HAS_PCI
>  	bool
> +
> +config HAS_PCI_ATS
> +	bool
> -- 
> 2.17.1
>