Re: [Qemu-devel] [PATCH v1 for-2.13 3/4] pc-bios/s390-ccw/net: Add support for pxelinux-style config files

[Viktor VM Mihajlovski <mihajlov@linux.vnet.ibm.com>]

On 19.04.2018 10:17, Thomas Huth wrote:
> On 19.04.2018 09:41, Viktor VM Mihajlovski wrote:
>> On 18.04.2018 14:31, Thomas Huth wrote:
>>> Since it is quite cumbersome to manually create a combined kernel with
>>> initrd image for network booting, we now support loading via pxelinux
>>> configuration files, too. In these files, the kernel, initrd and command
>>> line parameters can be specified seperately, and the firmware then takes
>>> care of glueing everything together in memory after the files have been
>>> downloaded.
[...]
>>> +static int net_try_direct_tftp_load(filename_ip_t *fn_ip)
>>> +{
>>> +    int rc;
>>> +    void *baseaddr = (void *)0x2000;  /* Load right after the low-core */
>>> +
>>> +    rc = tftp_load(fn_ip, baseaddr, KERNEL_MAX_SIZE - (long)baseaddr);
>>> +
>>> +    if (rc > 0 && rc < sizeof(cfgbuf) - 1) {
>>> +        /* Check whether it is a configuration file instead of a kernel */
>> That's interesting because treating the bootfile as pxe-ish config is
>> what DPM does. Which means that with this change the processor
>> architecture type 0x1f (Basic) will turn into a superset of 0x20
>> (Extended).
> 
> Is there any reference available what "basic" and "extended" exactly
> mean? I just know that there are these two values registered by you at
> the IANA:
> 
> https://www.iana.org/assignments/dhcpv6-parameters/dhcpv6-parameters.xhtml#processor-architecture
> 
> ... but I haven't seen a description of the differences of these two
> values yet.
> 
Yep, the IANA stuff is pretty terse for all architectures. In a
nutshell: 0x1f is standard DHCP-based boot (bootfile is a single
executable binary) and 0x20 serves a pxe-style config file instead.
In fact, "processor architecture identifier" is a misnomer, as it
describes a pair of processor architecture and firmware.
Since the QEMU firmware has two significant extensions now (insfile and
direct config file loading), it might be worthwhile to add a new
identifier value (say s390 QEMU PC-BIOS or similar) announcing the new
capabilities, so that a boot server admin can setup her system accordingly.
>> I guess this should be documented somewhere(TM) to avoid
>> confusion.
> 
> I plan to update https://wiki.qemu.org/Features/S390xNetworkBoot once
> the patches have been merged upstream.
> 
sounds good.
[...]

-- 
Regards,
  Viktor Mihajlovski