[SeaBIOS] [PATCH 1/2] scsi: ensure LUN0 is added first

[Paolo Bonzini]

On 27/09/2017 15:58, Kevin O'Connor wrote:
> On Wed, Sep 27, 2017 at 09:36:01AM +0200, Paolo Bonzini wrote:
>> On 21/06/2017 00:44, Kevin O'Connor wrote:
>>>> Yes, I think so.  I'm not sure why virtqueues are allocated
>>>> in low memory.  Either cargo culting, or a remain of when
>>>> virtio was a 16-bit driver, if it ever was.
>>> The 'struct drive_s' storage currently must be allocated in the
>>> f-segment so that the disk.c code can access some critical details of
>>> mapped drives when in 16bit mode.  However, we could change the code
>>> to allocate that data separately from the controller specific data and
>>> then move the controller specific data to a larger memory pool. 
>>
>> I don't think this is the issue.  virtqueues actually have been
>> allocated with memalign_high since 2015 (commit 6cfebb4e).
>>
>> virtio-blk is allocating 68 fseg bytes for the controller-specific data,
>> virtio-scsi only 16.  struct drive_s is about 40 bytes long.
> 
> What is the test case for reproducing the problem?

Do

  for i in $(seq 1 500); do
    echo -drive if=none,file=null-co://,id=null$i
    echo -device scsi-hd,lun=$i,drive=null$i;
  done > manydisks
  for i in $(seq 1 10); do
    echo -drive if=none,file=null-co://,id=null$i
    echo -device scsi-hd,lun=$i,drive=null$i;
  done > fewdisks

then

  qemu-kvm -device virtio-scsi-pci \
    -drive if=none,file=someos.qcow2,id=os \
    -device scsi-hd,lun=0,bootindex=0,drive=os $(cat manydisks)

does not respect bootindex=0 while

  qemu-kvm -device virtio-scsi-pci \
    -drive if=none,file=someos.qcow2,id=os \
    -device scsi-hd,lun=0,bootindex=0,drive=os $(cat fewdisks)

respects it.  The reason is that with "manydisks" you get many FSEG
allocation failures in virtio_scsi_init_lun.

Paolo

> 
> I can test with the patchset I posted earlier:
> 
> https://mail.coreboot.org/pipermail/seabios/2017-July/011452.html
> 
> which is also now at:
> 
> https://github.com/KevinOConnor/seabios/tree/work-drive-lowmem-20170711
> 
> 
> -Kevin
>