Re: [PATCH v2 2/4] xen/pci: Introduce new CONFIG_PCI_ATS flag for PCI ATS functionality.

[Bertrand Marquis <Bertrand.Marquis@xxxxxxx>]

> On 3 Nov 2020, at 15:59, Rahul Singh <Rahul.Singh@xxxxxxx> 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@xxxxxxx>
Reviewed-by: Bertrand Marquis <bertrand.marquis@xxxxxxx>

Cheers
Bertrand

> ---
> 
> Changes in v2:
> - Fixed return value of PCI ATS related functions when PCI_ATS is not enabled.
> - Make PCI_ATS user selectable kconfig option.
> 
> ---
> xen/drivers/passthrough/ats.h        | 26 ++++++++++++++++++++++++++
> xen/drivers/passthrough/x86/Makefile |  2 +-
> xen/drivers/pci/Kconfig              |  9 +++++++++
> 3 files changed, 36 insertions(+), 1 deletion(-)
> 
> diff --git a/xen/drivers/passthrough/ats.h b/xen/drivers/passthrough/ats.h
> index 22ae209b37..3a71fedcb4 100644
> --- a/xen/drivers/passthrough/ats.h
> +++ b/xen/drivers/passthrough/ats.h
> @@ -17,6 +17,8 @@
> 
> #include <xen/pci_regs.h>
> 
> +#ifdef CONFIG_PCI_ATS
> +
> #define ATS_REG_CAP    4
> #define ATS_REG_CTL    6
> #define ATS_QUEUE_DEPTH_MASK     0x1f
> @@ -48,5 +50,29 @@ 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
> +
> +#define ats_enabled (false)
> +
> +static inline int enable_ats_device(struct pci_dev *pdev,
> +                                    struct list_head *ats_list)
> +{
> +    return -EOPNOTSUPP;
> +}
> +
> +static inline void disable_ats_device(struct pci_dev *pdev) { }
> +
> +static inline int pci_ats_enabled(int seg, int bus, int devfn)
> +{
> +    return 0;
> +}
> +
> +static inline int pci_ats_device(int seg, int bus, int devfn)
> +{
> +    return 0;
> +}
> +
> +#endif /* CONFIG_PCI_ATS */
> +
> #endif /* _ATS_H_ */
> 
> diff --git a/xen/drivers/passthrough/x86/Makefile 
> b/xen/drivers/passthrough/x86/Makefile
> index a70cf9460d..aa515c680d 100644
> --- a/xen/drivers/passthrough/x86/Makefile
> +++ b/xen/drivers/passthrough/x86/Makefile
> @@ -1,2 +1,2 @@
> -obj-y += ats.o
> +obj-$(CONFIG_PCI_ATS) += ats.o
> obj-y += iommu.o
> diff --git a/xen/drivers/pci/Kconfig b/xen/drivers/pci/Kconfig
> index 7da03fa13b..3cb79ea954 100644
> --- a/xen/drivers/pci/Kconfig
> +++ b/xen/drivers/pci/Kconfig
> @@ -1,3 +1,12 @@
> 
> config HAS_PCI
>       bool
> +
> +config PCI_ATS
> +     bool "PCI ATS support"
> +     default y
> +     depends on X86 && HAS_PCI
> +     ---help---
> +      Enable PCI Address Translation Services.
> +
> +      If unsure, say Y.
> -- 
> 2.17.1
>