Re: [Xen-devel] [v5][PATCH 11/16] tools/libxl: detect and avoid conflicts with RDM

["Chen, Tiejun" <tiejun.chen@xxxxxxxxx>]

On 2015/7/7 19:57, Ian Jackson wrote:
> Tiejun Chen writes ("[v5][PATCH 11/16] tools/libxl: detect and avoid conflicts with 
> RDM"):
> > While building a VM, HVM domain builder provides struct hvm_info_table{}
> > to help hvmloader. Currently it includes two fields to construct guest
> > e820 table by hvmloader, low_mem_pgend and high_mem_pgend. So we should
> > check them to fix any conflict with RDM.
> ...
> > +    *nr_entries = 0;
> > +    rc = xc_reserved_device_memory_map(CTX->xch, flag, seg, bus, devfn,
> > +                                       NULL, nr_entries);
> > +    assert(rc <= 0);
> > +    /* "0" means we have no any rdm entry. */
> > +    if (!rc)
> > +        goto out;
> I think the error handling here is wrong.  Certainly `rc' should not
> be used for a libxc return.
Nope, we don't return rc directly. In any case of error, rc is reset as 
"ERROR_FAIL" finally.
> See tools/libxl/CODING_STYLE.  I know that much of the existing code
> uses rc for libxc returns but this is deprecated, and please don't
> make more of it.
>
> > +    if (errno == ENOBUFS) {
> > +        *xrdm = libxl__malloc(gc,
> > +                              *nr_entries *
> > +                              sizeof(xen_reserved_device_memory_t));
> > +        rc = xc_reserved_device_memory_map(CTX->xch, flag, seg, bus, devfn,
> > +                                           *xrdm, nr_entries);
> This might be less code, and a bit clearer, if it were a loop rather
> than two calls with the second in an if.
Sorry I can't understand completely what you want to do. But I really 
agree we should improve this chunk of codes, what about this?
    if (errno != ENOBUFS) {
        rc = ERROR_FAIL;
        goto out;
    }

    *xrdm = libxl__malloc(gc,
                          *nr_entries * 
sizeof(xen_reserved_device_memory_t));
    rc = xc_reserved_device_memory_map(CTX->xch, flag, seg, bus, devfn,
                                       *xrdm, nr_entries);
    if (rc)
        rc = ERROR_FAIL;

 out:
    if (rc) {
        *nr_entries = 0;
        *xrdm = NULL;
        LOG(ERROR, "Could not get reserved device memory maps.\n");
    }
    return rc;

I think this make more readable and clear.

> ...
> > +        if(d_config->rdms[i].flag == LIBXL_RDM_RESERVE_FLAG_STRICT) {
>               ^
> Missing space.
Fixed.

Thanks
Tiejun

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel