[ipxe-devel] SRP booting linux, SRP volume with ISO stops seeing itself

[james harvey]

In other words, is offset to SCSI Subtable always going to be 48, and
offset to SRP Subtable always going to be 56?  And, is offset to SRP
Subtable always going to be 0 or 88?

On Sun, Jul 17, 2016 at 6:09 AM, james harvey <jamespharvey20 at gmail.com> wrote:
> I'm picking up this project again.  Wanted to make sure such a tool
> hadn't been written since January.
>
> Also, am I correctly understanding the sBFT documentation, that there
> is always exactly 1 SCSI Subtable and 1 SRP Subtable, and either 0 or
> 1 IB Subtables?
>
> If there's always 1 SCSI Subtable and always 1 SRP Subtable, I'm
> confused why there's an offset to those since at that point I'm not
> seeing anything variable length.
>
> On Wed, Jan 27, 2016 at 7:17 PM, Michael Brown <mcb30 at ipxe.org> wrote:
>> On 08/01/16 02:19, james harvey wrote:
>>>
>>> Before I keep going down the hole, let me make sure my plan isn't
>>> futile.  I want to make a diskless system, by having iPXE in my
>>> InfiniBand card's ROM, and being able to boot an Arch Linux Live ISO
>>> (custom built with srp kernel modules) exported as a SRP volume backed
>>> by the ISO, and install on other SRP volumes which are backed by LVM
>>> volumes.
>>>
>>> I have a real general idea of how the iPXE to kernel handoff works,
>>> through the iBFT (iSCSI Boot Firmware Table.)  Since I'm using SRP
>>> rather than iSCSI, is the iBFT still used?  If not, how does the SRP
>>> connection get handed off, with all the variables needed for an SRP
>>> connection?
>>
>>
>> There is an SRP boot firmware table constructed (the sBFT).  This is
>> nominally documented at
>>
>>   http://ipxe.org/srp/sbft
>>
>> However, I'm not aware of any Linux userspace tools that are capable of
>> parsing that structure.  It should be fairly easy to create such a tool,
>> which would scan base memory for the sBFT signature, verify the checksum,
>> extract the fields, and then write the relevant values into sysfs to
>> initiate the connection.
>>
>> I thought I had written such a tool back in 2009, but all I can find
>> relating to it is the proposal document.  It seems to have been an abandoned
>> project back then.
>>
>> Michael