Re: [Qemu-devel] [PATCH v2 1/7] bootindex: add modify_boot_device_path function

[Gonglei (Arei)]

Hi,

> -----Original Message-----
> From: Gonglei (Arei)
> Sent: Monday, July 28, 2014 6:16 PM
> Subject: RE: [PATCH v2 1/7] bootindex: add modify_boot_device_path function
> 
> > -----Original Message-----
> > From: Gerd Hoffmann [mailto:address@hidden
> > Sent: Monday, July 28, 2014 6:02 PM
> > Subject: Re: [PATCH v2 1/7] bootindex: add modify_boot_device_path function
> >
> >   Hi,
> >
> > > > > > I think it is ok to allow only *changing* the bootindex.
> > > > > >
> > > > > Yes, that's no problem.
> > > >
> > > > But then yoy always  will have a old entry where you can take the suffix
> > > > from, and you don't need the suffix as parameter for the monitor
> > > > command.
> > > >
> > > No, optional.
> >
> > > Because the bootindex property is not a necessary property for devices.
> > > If a device, such as IDE cdrom haven't attach the bootindex in qemu 
> > > booting
> > > command line, the global fw_boot_order will not have its entry.
> >
> > I'd suggest to simply not support this and throw an error then.
> >
> Ok.
> 
> > > So, we should
> > > save the suffix as parameter.
> >
> > I think it is a bad idea to have the suffix as monitor command
> > parameter.  It is a implementation detail which the monitor users should
> > not have to worry about.
> >
> Yes. Actually I also have this misgivings.
> 
> > Easiest way to do this is to allow *changing* an existing bootindex
> > entry only, and not support *adding* new boot entries.  The user has to
> > set a bootindex for any device it might want to boot from in the future
> > then.  I think this is acceptable.
> >
> Hmm..
> 
> > If you want support adding bootentries at runtime (and it probably makes
> > sense to support removing entries too in that case) the suffix handling
> > should be reworked.  The suffix could be stored in DeviceState instead
> > of being passed to the add_bootentry function, so you can add boot
> > entries later on without expecting the user to know what the correct
> > suffix is.
> >
> That's a good idea! I think this is a good improvement.
> 
> Any other comments? Thanks!
> 
Maybe we should save the suffix as parameter in add_boot_device_path()

There are two reasons:

1. the floppy device may have two bootindex, which configure as below:
 " -global isa-fdc.driveA=drive-fdc0-0-0, bootindexA=xxx \ 
  -global isa-fdc.driveB=drive-fdc0-0-1 bootindexB=xxx \"
 We can see it in isabus_fdc_realize() [hw/block/fdc.c]

2. The option rom don't need pass dev to add_bootentry, 
  which realized in rom_add_file() [hw/core/loader.c]
  
in those situation, we have to pass suffix to add_bootentry function.

Best regards,
-Gonglei