Re: [Xen-devel] [PATCH] pci: constify domain parameter of pci_get_pdev_by_domain

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 08/09/17 14:34, Roger Pau Monne wrote:
> While there fix the indentation.
>
> Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> ---
> Cc: Jan Beulich <jbeulich@xxxxxxxx>
> Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> Cc: George Dunlap <George.Dunlap@xxxxxxxxxxxxx>
> Cc: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
> Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
> Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>
> Cc: Tim Deegan <tim@xxxxxxx>
> Cc: Wei Liu <wei.liu2@xxxxxxxxxx>
> ---
>  xen/drivers/passthrough/pci.c | 4 ++--
>  xen/include/xen/pci.h         | 4 ++--
>  2 files changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/xen/drivers/passthrough/pci.c b/xen/drivers/passthrough/pci.c
> index 74829e5748..469dfc6c3d 100644
> --- a/xen/drivers/passthrough/pci.c
> +++ b/xen/drivers/passthrough/pci.c
> @@ -532,8 +532,8 @@ struct pci_dev *pci_get_real_pdev(int seg, int bus, int 
> devfn)
>      return pdev;
>  }
>  
> -struct pci_dev *pci_get_pdev_by_domain(
> -    struct domain *d, int seg, int bus, int devfn)
> +struct pci_dev *pci_get_pdev_by_domain(const struct domain *d, int seg,
> +                                       int bus, int devfn)

I know this isn't strictly related to the patch, but having 3 register
parameters (and load of places elsewhere) here is extremely wasteful for
register scheduling.  Could we introduce:

typedef union {
    uint32_t sbdf;
    struct {
        uint16_t  f : 3,  /* Function */
                  d : 5,  /* Device   */
                  b : 8;  /* Bus      */
        uint16_t s; /* Segment  */
    };
} pci_sbdf_t;

and try to start using it?

~Andrew

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