On Fri, 5 Oct 2012 10:34:16 +1000, David Gibson <d...@au1.ibm.com> wrote: > On Thu, Oct 04, 2012 at 04:25:28PM +0530, Avik Sil wrote: > > On 09/27/2012 03:21 PM, Gleb Natapov wrote: > > >On Thu, Sep 27, 2012 at 11:33:31AM +0200, Alexander Graf wrote: > > >> > > >>On 27.09.2012, at 11:29, Benjamin Herrenschmidt wrote: > > >> > > >>>On Thu, 2012-09-27 at 14:51 +0530, Avik Sil wrote: > > >>>>Hi, > > >>>> > > >>>>We would like to get a method to boot from devices provided in -boot > > >>>>arguments in qemu when the 'boot-device' is set in nvram for pseries > > >>>>machine. I mean the boot device specified in -boot should get a > > >>>>precedence over the 'boot-device' specified in nvram. > > >>>> > > >>>>At the same time, when -boot is not provided, i.e., the default boot > > >>>>order "cad" is present, the device specified in nvram 'boot-device' > > >>>>should get precedence if it is set. > > >>>> > > >>>>What should be the elegant way to implement this requirement? > > >>>>Suggestions welcome. > > >>> > > >>>Actually I think it's a more open question. We have essentially two > > >>>things at play here: > > >>> > > >>>- With the new nvram model, the firmware can store a boot device > > >>>reference in it, which is standard OF practice, and in fact the various > > >>>distro installers are going to do just that > > >>> > > >>>- Qemu has its own boot order thingy via -boot, which we loosely > > >>>translate as c = first bootable disk we find (actually first disk we > > >>>find, we should probably make the algorithm a bit smarter), d = first > > >>>cdrom we find, n = network , ... We pass that selection (boot list) down > > >>>to SLOF via a device-tree property. > > >>> > > >>>The question is thus what precedence should we give them. I was > > >>>initially thinking that an explicit qemu boot list should override the > > >>>firmware nvram setting but I'm now not that sure anymore. > > >>> > > >>>The -boot list is at best a "blurry" indication of what type of device > > >>>the user wants ... The firmware setting in nvram is precise. > > >> > > >>IIRC gleb had implemented a specific boot order thing. Gleb, mind to > > >>enlighten us? :) > > >> > > >Yes, forget about -boot. It is deprecated :) You should use bootindex > > >(device property) to set boot priority. It constructs OF device path > > >and passes it to firmware. There is nothing "blurry" about OF device > > >path. The problem is that it works reasonably well with legacy BIOS > > >since it is enough to specify device to boot from, but with EFI (OF is > > >the same I guess) it is not enough to point to a device to boot from, > > >but you also need to specify a file you want to boot and this is where > > >bootindex approach fails. If EFI would specify default file to boot from > > >firmware could have used it, but EFI specifies it only for removable media > > >(what media is not removable this days, especially with virtualization?). > > >We can add qemu parameter to specify file to boot, but how users should > > >know the name of the file? > > > > > I looked at the bootindex stuff and found that when the bootindex is > > specified for the disk and cdrom it generates a string like: > > > > "/spapr-vio-bridge/spapr-vscsi/channel@0/disk@0,1 > > /spapr-vio-bridge/spapr-vscsi/channel@0/disk@0,0" > > Ok, so I've just started looking at the bootindex stuff. What > function is generating these strings?
get_boot_devices_list gives you the above > > We should also be able to get the raw bootindex values for a qdev, > yes? I was thinking we could instead copy those values into the > device tree when we populate it. The trouble is that we don't > actually generate (in qemu) nodes for individual disks under a vscsi, > or for individual PCI devices under the host bridge (that's done by > SLOF). Still thinking... > > An aside, I'm thinking that once we do get bootindex working, then > boot devices specified in NVRAM should have priority below all devices > with explicit supplied bootindex, but above any that don't. Does that > seem right to you? Even if the bootindex is taken care, there is still -boot that has to be handled. Or we just need to drop -boot handling? In that case what should we look at when there is no boot-index and nothing in nvram. Regards Nikunj