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Date: Mon, 21 Mar 2016 15:39:54 -0600
From: Alex Williamson <alex.williamson@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH v4 05/10] vfio: extending function
 vfio_pci_host_match to support mask func number
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To: Cao jin <caoj.fnst@cn.fujitsu.com>
Cc: chen.fan.fnst@cn.fujitsu.com, izumi.taku@jp.fujitsu.com, qemu-devel@nongnu.org, mst@redhat.com

On Mon, 21 Mar 2016 18:08:41 +0800
Cao jin <caoj.fnst@cn.fujitsu.com> wrote:

> From: Chen Fan <chen.fan.fnst@cn.fujitsu.com>
> 
> Signed-off-by: Chen Fan <chen.fan.fnst@cn.fujitsu.com>
> ---
>  hw/vfio/pci.c | 29 ++++++++++++++++++++---------
>  1 file changed, 20 insertions(+), 9 deletions(-)
> 
> diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
> index 0516d94..8842b7f 100644
> --- a/hw/vfio/pci.c
> +++ b/hw/vfio/pci.c
> @@ -2060,14 +2060,25 @@ static void vfio_pci_post_reset(VFIOPCIDevice *vdev)
>      vfio_intx_enable(vdev);
>  }
>  
> -static bool vfio_pci_host_match(PCIHostDeviceAddress *addr, const char *name)
> +#define HOST_CMP_FUNC_MASK       (1 << 0)
> +static bool vfio_pci_host_match(PCIHostDeviceAddress *addr, const char *name,
> +                                uint8_t mask)
>  {
> -    char tmp[13];
> +    PCIHostDeviceAddress tmp;
>  
> -    sprintf(tmp, "%04x:%02x:%02x.%1x", addr->domain,
> -            addr->bus, addr->slot, addr->function);
> +    if (strlen(name) != 12) {
> +        return false;
> +    }
> +
> +    if (sscanf(name, "%04x:%02x:%02x.%1x", &tmp.domain,
> +               &tmp.bus, &tmp.slot, &tmp.function) != 4) {
> +        return false;
> +    }
>  
> -    return (strcmp(tmp, name) == 0);
> +    return (tmp.domain == addr->domain && tmp.bus == addr->bus &&
> +            tmp.slot == addr->slot &&
> +            ((mask & HOST_CMP_FUNC_MASK) ?
> +                1 : (tmp.function == addr->function)));
>  }

I'd probably go for something like:

static int vfio_pci_name_to_addr(const char *name, PCIHostDeviceAddress *addr)
{
    if (strlen(name) != 12 ||
        sscanf(name, "%04x:%02x:%02x.%1x", &addr->domain,
               &addr->bus, &addr->slot, &addr->function) != 4 ) {
        return -EINVAL;
    }

    return 0;
}

static bool vfio_pci_host_match(PCIHostDeviceAddress *addr, const char *name)
{
    PCIHostDeviceAddress tmp;

    if (vfio_pci_name_to_addr(name, &tmp)) {
        return false;
    }

    return (tmp.domain == addr->domain && tmp.bus == addr->bus &&
            tmp.slot == addr->slot && tmp.function == addr->function);
}

Then a _slot version that avoids skips the function comparison.  The
mask argument doesn't make much sense for such a simple function when
the code duplication is trivial.