Re: [Xen-devel] [PATCH xm/xl enhancements for vptm 5/6] make devid a libxl type

[Matthew Fioravante <matthew.fioravante@xxxxxxxxxx>]

On 09/25/2012 06:36 AM, Ian Campbell wrote:
> On Fri, 2012-09-21 at 20:20 +0100, Matthew Fioravante wrote:
>> This fixes a bug in libxl where device ids are not initialized properly.
>> The devid field for each device is set to be an integer type which are
>> always initialized to 0.
>>
>> This makes the xl DEV-attach commands always fail to add more than one
>> device, because each time the device id is initialized to 0, when it
>> should be initialized to -1, which in the code will trigger a search for
>> free id.
> Which of the DEV-attach commands can be used to add more than one
> device?
network-attach, block-attach, and also my vtpm-attach.
>
> Where is the code to do the search? I had a look in the disk and network
> cases and couldn't find it.
libxl.c

void libxl__device_nic_add(

    if (nic->devid == -1) {
        if (!(dompath = libxl__xs_get_dompath(gc, domid))) {
            rc = ERROR_FAIL;
            goto out_free;
        }
        if (!(l = libxl__xs_directory(gc, XBT_NULL,
                                     libxl__sprintf(gc, "%s/device/vif",
dompath), &nb))) {
            nic->devid = 0;
        } else {
            nic->devid = strtoul(l[nb - 1], NULL, 10) + 1;
        }
    }

Right now, nic-devid is 0 on attach. So it always tries to use 0. When
you do a network-attach twice,
the second time it trys and fails to create device/vif/0

>
>> diff --git a/tools/ocaml/libs/xs/xs.mli b/tools/ocaml/libs/xs/xs.mli
>> --- a/tools/ocaml/libs/xs/xs.mli
>> +++ b/tools/ocaml/libs/xs/xs.mli
>> @@ -27,6 +27,7 @@ exception Failed_to_connect
>>  type perms = Xsraw.perms
>>  
>>  type domid = int
>> +type devid = int
> I can see why these were needed in the xl modules, but I don't see how
> this type can be required in the xenstore ones.
It shouldn't be required for xenstore or xc. The problem is they won't
compile without it because of the way the ocaml build system works. As
far as I understand it creates types for xl, xc, and xs from the
libxl_types.idl. Either the build system needs to be changed, or devid
needs to be a type in all libraries, or we find some other way to fix
this initialization bug.
>
> Ian.
>

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