Re: [RFC XEN PATCH v11 7/8] tools: Add new function to get gsi from dev

[Jan Beulich <jbeulich@xxxxxxxx>]

On 30.06.2024 14:33, Jiqian Chen wrote:
> --- a/tools/libs/ctrl/xc_physdev.c
> +++ b/tools/libs/ctrl/xc_physdev.c
> @@ -111,3 +111,38 @@ int xc_physdev_unmap_pirq(xc_interface *xch,
>      return rc;
>  }
>  
> +int xc_physdev_gsi_from_pcidev(xc_interface *xch, uint32_t sbdf)
> +{
> +    int rc = -1;
> +
> +#if defined(__linux__)
> +    int fd;
> +    privcmd_gsi_from_pcidev_t dev_gsi = {
> +        .sbdf = sbdf,
> +        .gsi = 0,
> +    };
> +
> +    fd = open("/dev/xen/privcmd", O_RDWR);
> +
> +    if (fd < 0 && (errno == ENOENT || errno == ENXIO || errno == ENODEV)) {
> +        /* Fallback to /proc/xen/privcmd */
> +        fd = open("/proc/xen/privcmd", O_RDWR);
> +    }
> +
> +    if (fd < 0) {
> +        PERROR("Could not obtain handle on privileged command interface");
> +        return rc;
> +    }
> +
> +    rc = ioctl(fd, IOCTL_PRIVCMD_GSI_FROM_PCIDEV, &dev_gsi);
> +    close(fd);
> +
> +    if (rc) {
> +        PERROR("Failed to get gsi from dev");
> +    } else {
> +        rc = dev_gsi.gsi;
> +    }
> +#endif
> +
> +    return rc;
> +}

I realize Anthony had asked to move this out of libxencall, yet doing it like
this (without really abstracting away the OS specifics) doesn't look quite
right either. In particular the opening of /dev/xen/privcmd looks questionable
to now have yet another instance in yet another library. Couldn't we split
osdep_xencall_open(), making available its former half for use here and in the
other two libraries? Of course that'll still leave the ioctl() invocation,
which necessarily is OS-specific, too.

Jan