Re: [Qemu-devel] [Qemu-ppc] Qemu boot device precedence over nvram boot-device setting

Re: [Qemu-devel] [Qemu-ppc] Qemu boot device precedence over nvram boot-device setting

[Alexander Graf]

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? :)

> However if we make the nvram override qemu, then it's trickier to
> force-boot from, let's say, a rescue CD. The user would have to stop the
> SLOF boot process by pressing a key then manually type something like
> "boot cdrom".
> 
> Maybe the right approach is "in between", and is that the primary driver
> is the -boot argument. For each entry in the boot list, if it's "c", use
> the configured boot-device or fallback to the automatic guess SLOF tries
> to do today in absence of a boot-device. If it's "d" or "n" force it
> respectively to cdrom or network...
> 
> I think there is no perfect solution here. What do you guys think is the
> less user unfriendly ?

I think the command line should override anything user specified. So basically:

  * user defined -boot option (or bootindex magic from Gleb)
  * nvram
  * fallback to default

> Eventually we should try to implement some sort of interactive boot
> device selection in SLOF, such as SMS does on pseries, but that will
> take a bit of time.

That would be en par with the bootmenu on x86 :). Please check out how x86 models these things. It could sure be interesting for pseries.


Alex

Re: [Qemu-devel] [Qemu-ppc] Qemu boot device precedence over nvram boot-device setting

[Benjamin Herrenschmidt]

On Thu, 2012-09-27 at 11:33 +0200, Alexander Graf wrote:
> 
> I think the command line should override anything user specified. So
> basically:
> 
>   * user defined -boot option (or bootindex magic from Gleb)
>   * nvram
>   * fallback to default
> 
> > Eventually we should try to implement some sort of interactive boot
> > device selection in SLOF, such as SMS does on pseries, but that will
> > take a bit of time.

Ok but that means we need a way to know that an explicit -boot argument
was passed vs. the default built-in list. I don't think vl.c gives us
that today, does it ?
 
> That would be en par with the bootmenu on x86 :). Please check out how
> x86 models these things. It could sure be interesting for pseries.

Hrm... might apply ... or not. If we can specific an explicit qdev on
qemu command line, then it's going to be an interesting exercise to tell
SLOF about it (PCI devices come to mind).

Cheers
Ben.

Re: [Qemu-devel] [Qemu-ppc] Qemu boot device precedence over nvram boot-device setting

[Alexander Graf]

On 27.09.2012, at 11:35, Benjamin Herrenschmidt wrote:

> On Thu, 2012-09-27 at 11:33 +0200, Alexander Graf wrote:
>> 
>> I think the command line should override anything user specified. So
>> basically:
>> 
>>  * user defined -boot option (or bootindex magic from Gleb)
>>  * nvram
>>  * fallback to default
>> 
>>> Eventually we should try to implement some sort of interactive boot
>>> device selection in SLOF, such as SMS does on pseries, but that will
>>> take a bit of time.
> 
> Ok but that means we need a way to know that an explicit -boot argument
> was passed vs. the default built-in list. I don't think vl.c gives us
> that today, does it ?

If it doesn't, we add that logic :).

> 
>> That would be en par with the bootmenu on x86 :). Please check out how
>> x86 models these things. It could sure be interesting for pseries.
> 
> Hrm... might apply ... or not. If we can specific an explicit qdev on
> qemu command line, then it's going to be an interesting exercise to tell
> SLOF about it (PCI devices come to mind).

... which is the same problem x86 has to convert qdev devices to option rom magic numbers. Really, the problems are very similar :)


Alex

Re: [Qemu-devel] [Qemu-ppc] Qemu boot device precedence over nvram boot-device setting

[Gleb Natapov]

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?

> > However if we make the nvram override qemu, then it's trickier to
> > force-boot from, let's say, a rescue CD. The user would have to stop the
> > SLOF boot process by pressing a key then manually type something like
> > "boot cdrom".
> > 
> > Maybe the right approach is "in between", and is that the primary driver
> > is the -boot argument. For each entry in the boot list, if it's "c", use
> > the configured boot-device or fallback to the automatic guess SLOF tries
> > to do today in absence of a boot-device. If it's "d" or "n" force it
> > respectively to cdrom or network...
> > 
> > I think there is no perfect solution here. What do you guys think is the
> > less user unfriendly ?
> 
> I think the command line should override anything user specified. So basically:
> 
>   * user defined -boot option (or bootindex magic from Gleb)
>   * nvram
>   * fallback to default
> 
> > Eventually we should try to implement some sort of interactive boot
> > device selection in SLOF, such as SMS does on pseries, but that will
> > take a bit of time.
> 
> That would be en par with the bootmenu on x86 :). Please check out how x86 models these things. It could sure be interesting for pseries.
> 
> 
> Alex

--
			Gleb.

Re: [Qemu-devel] [Qemu-ppc] Qemu boot device precedence over nvram boot-device setting

[Nikunj A Dadhania]

On Thu, 27 Sep 2012 11:51:36 +0200, Gleb Natapov <gleb@redhat.com> 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. 

If the user does not set bootindex, qemu would decide the bootindex?  

If it does, there will be a default bootindex. Then the problem still
remains, qemu decided the boot-order, in which case we would want to
pick the nvram based setting. This is again difficult to distinguish.

> 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.

By file I suppose you mean OF device-path. 

> > 
> > I think the command line should override anything user specified. So basically:
> > 
> >   * user defined -boot option (or bootindex magic from Gleb)
> >   * nvram
> >   * fallback to default
> > 

Regards
Nikunj

Re: [Qemu-devel] [Qemu-ppc] Qemu boot device precedence over nvram boot-device setting

[Gleb Natapov]

On Thu, Sep 27, 2012 at 03:35:53PM +0530, Nikunj A Dadhania wrote:
> On Thu, 27 Sep 2012 11:51:36 +0200, Gleb Natapov <gleb@redhat.com> 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. 
> 
> If the user does not set bootindex, qemu would decide the bootindex?  
> 
No. Firmware decides. QEMU just tells to firmware that it does not have
bootindex.

> If it does, there will be a default bootindex. Then the problem still
> remains, qemu decided the boot-order, in which case we would want to
> pick the nvram based setting. This is again difficult to distinguish.
> 
> > 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.
> 
> By file I suppose you mean OF device-path. 
> 
No. By file I mean a file on dedicated EFI FAT partition that EFI loads
during boot.  I do not know if OF has something similar.

> > > 
> > > I think the command line should override anything user specified. So basically:
> > > 
> > >   * user defined -boot option (or bootindex magic from Gleb)
> > >   * nvram
> > >   * fallback to default
> > > 
> 
> Regards
> Nikunj

--
			Gleb.

Re: [Qemu-devel] [Qemu-ppc] Qemu boot device precedence over nvram boot-device setting

[Nikunj A Dadhania]

On Thu, 27 Sep 2012 12:13:05 +0200, Gleb Natapov <gleb@redhat.com> wrote:
> On Thu, Sep 27, 2012 at 03:35:53PM +0530, Nikunj A Dadhania wrote:
> > 
> > If the user does not set bootindex, qemu would decide the bootindex?  
> > 
> No. Firmware decides. QEMU just tells to firmware that it does not have
> bootindex.

Ok. That should work in that case, we need to make sure that bootindex
is being send via device-tree. I do not see such code in place
currently.

> 
> > If it does, there will be a default bootindex. Then the problem still
> > remains, qemu decided the boot-order, in which case we would want to
> > pick the nvram based setting. This is again difficult to distinguish.
> > 
> > > 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.
> > 
> > By file I suppose you mean OF device-path. 
> > 
> No. By file I mean a file on dedicated EFI FAT partition that EFI loads
> during boot.  I do not know if OF has something similar.
> 
No, it just needs the device-path. Rest it figures out.

Regards
Nikunj

Re: [Qemu-devel] [Qemu-ppc] Qemu boot device precedence over nvram boot-device setting

[Gleb Natapov]

On Thu, Sep 27, 2012 at 04:04:54PM +0530, Nikunj A Dadhania wrote:
> On Thu, 27 Sep 2012 12:13:05 +0200, Gleb Natapov <gleb@redhat.com> wrote:
> > On Thu, Sep 27, 2012 at 03:35:53PM +0530, Nikunj A Dadhania wrote:
> > > 
> > > If the user does not set bootindex, qemu would decide the bootindex?  
> > > 
> > No. Firmware decides. QEMU just tells to firmware that it does not have
> > bootindex.
> 
> Ok. That should work in that case, we need to make sure that bootindex
> is being send via device-tree. I do not see such code in place
> currently.
> 
It is sent to firmware via PV fw_cfg interface in "bootorder" file.

> > 
> > > If it does, there will be a default bootindex. Then the problem still
> > > remains, qemu decided the boot-order, in which case we would want to
> > > pick the nvram based setting. This is again difficult to distinguish.
> > > 
> > > > 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.
> > > 
> > > By file I suppose you mean OF device-path. 
> > > 
> > No. By file I mean a file on dedicated EFI FAT partition that EFI loads
> > during boot.  I do not know if OF has something similar.
> > 
> No, it just needs the device-path. Rest it figures out.
> 
> Regards
> Nikunj

--
			Gleb.

Re: [Qemu-devel] [Qemu-ppc] Qemu boot device precedence over nvram boot-device setting

[Benjamin Herrenschmidt]

On Thu, 2012-09-27 at 11:51 +0200, Gleb Natapov wrote:

> 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. 

Of course it is ;-) They are perfectly precise down to the device for
which qemu generates the device-tree ... and from there it requires the
firmware and qemu to both agree on how they are constructed, and it
becomes totally unpredictable once things like f-code drivers coming
from adapter ROMs enter the picture.

In fact, we can probably get them right down the the PCI device for PCI
(for which we don't currently construct the device nodes in qemu, but we
can 'guess'). And we can probably get the right unit address for vscsi,
virtio-scsi, etc... but that's about it.

> 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?

Cheers,
Ben.

Re: [Qemu-devel] [Qemu-ppc] Qemu boot device precedence over nvram boot-device setting

[Gleb Natapov]

On Thu, Sep 27, 2012 at 08:21:43PM +1000, Benjamin Herrenschmidt wrote:
> On Thu, 2012-09-27 at 11:51 +0200, Gleb Natapov wrote:
> 
> > 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. 
> 
> Of course it is ;-) They are perfectly precise down to the device for
> which qemu generates the device-tree ... and from there it requires the
> firmware and qemu to both agree on how they are constructed, and it
> becomes totally unpredictable once things like f-code drivers coming
> from adapter ROMs enter the picture.
> 
If QEMU generates OF device path that can't be used by firmware uniquely
identify the device this is QEMU bug. You are correct about ROMs though.
At least on a PC single ROM can register multiple boot vectors and since
QEMU knows nothing about them it can't prioritize between them. It's sad
if OF has similar problem.

> In fact, we can probably get them right down the the PCI device for PCI
> (for which we don't currently construct the device nodes in qemu, but we
> can 'guess'). And we can probably get the right unit address for vscsi,
> virtio-scsi, etc... but that's about it.
What more do you need?

> 
> > 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?
> 
> Cheers,
> Ben.
> 
> 

--
			Gleb.

Re: [Qemu-devel] [Qemu-ppc] Qemu boot device precedence over nvram boot-device setting

[Jordan Justen]

On Thu, Sep 27, 2012 at 2:51 AM, Gleb Natapov <gleb@redhat.com> wrote:
> 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?).

The UEFI spec now mentions under "Non-removable Media Boot Behavior"
that \efi\boot\boot*.efi can be used as a fallback for non-removable
media.

-Jordan

Re: [Qemu-devel] [Qemu-ppc] Qemu boot device precedence over nvram boot-device setting

[Avik Sil]

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"

Now converting/translating this to OF device path is going to be much 
trickier and might not be proper. So I propose a simple solution by 
introducing a global flag that checks if explicit -boot parameter is 
provided or not. The presence of this parameter is verified in SLOF 
firmware. The flag had to be introduced as boot_devices defaults to 
"cad" instead of null and passed to machine->init().

diff --git a/hw/spapr.c b/hw/spapr.c
index e6bf522..673bcc8 100644
--- a/hw/spapr.c
+++ b/hw/spapr.c
@@ -284,7 +284,8 @@ static void *spapr_create_fdt_skel(const char 
*cpu_model,

          _FDT((fdt_property(fdt, "qemu,boot-kernel", &kprop, 
sizeof(kprop))));
      }
-    _FDT((fdt_property_string(fdt, "qemu,boot-device", boot_device)));
+    if (!default_boot_order)
+        _FDT((fdt_property_string(fdt, "qemu,boot-device", boot_device)));
      _FDT((fdt_property_cell(fdt, "qemu,graphic-width", graphic_width)));
      _FDT((fdt_property_cell(fdt, "qemu,graphic-height", graphic_height)));
      _FDT((fdt_property_cell(fdt, "qemu,graphic-depth", graphic_depth)));
diff --git a/sysemu.h b/sysemu.h
index 65552ac..f0822b4 100644
--- a/sysemu.h
+++ b/sysemu.h
@@ -129,6 +129,7 @@ extern int no_shutdown;
  extern int semihosting_enabled;
  extern int old_param;
  extern int boot_menu;
+extern int default_boot_order;
  extern uint8_t *boot_splash_filedata;
  extern int boot_splash_filedata_size;
  extern uint8_t qemu_extra_params_fw[2];
diff --git a/vl.c b/vl.c
index 48049ef..bf369e6 100644
--- a/vl.c
+++ b/vl.c
@@ -230,6 +230,7 @@ int ctrl_grab = 0;
  unsigned int nb_prom_envs = 0;
  const char *prom_envs[MAX_PROM_ENVS];
  int boot_menu;
+int default_boot_order = 1;
  uint8_t *boot_splash_filedata;
  int boot_splash_filedata_size;
  uint8_t qemu_extra_params_fw[2];
@@ -2668,6 +2669,7 @@ int main(int argc, char **argv, char **envp)
                          qemu_opts_parse(qemu_find_opts("boot-opts"),
                                          optarg, 0);
                      }
+                    default_boot_order = 0;
                  }
                  break;
              case QEMU_OPTION_fda:


Comments welcome.

>>> However if we make the nvram override qemu, then it's trickier to
>>> force-boot from, let's say, a rescue CD. The user would have to stop the
>>> SLOF boot process by pressing a key then manually type something like
>>> "boot cdrom".
>>>
>>> Maybe the right approach is "in between", and is that the primary driver
>>> is the -boot argument. For each entry in the boot list, if it's "c", use
>>> the configured boot-device or fallback to the automatic guess SLOF tries
>>> to do today in absence of a boot-device. If it's "d" or "n" force it
>>> respectively to cdrom or network...
>>>
>>> I think there is no perfect solution here. What do you guys think is the
>>> less user unfriendly ?
>>
>> I think the command line should override anything user specified. So basically:
>>
>>    * user defined -boot option (or bootindex magic from Gleb)
>>    * nvram
>>    * fallback to default
>>
>>> Eventually we should try to implement some sort of interactive boot
>>> device selection in SLOF, such as SMS does on pseries, but that will
>>> take a bit of time.
>>
>> That would be en par with the bootmenu on x86 :). Please check out how x86 models these things. It could sure be interesting for pseries.
>>
>>
>> Alex
>
> --
> 			Gleb.
>
>
Regards,
Avik

Re: [Qemu-devel] [Qemu-ppc] Qemu boot device precedence over nvram boot-device setting

[Gleb Natapov]

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"
> 
> Now converting/translating this to OF device path is going to be
> much trickier and might not be proper. So I propose a simple
> solution by introducing a global flag that checks if explicit -boot
> parameter is provided or not. The presence of this parameter is
> verified in SLOF firmware. The flag had to be introduced as
> boot_devices defaults to "cad" instead of null and passed to
> machine->init().
> 
So you want to hack around the problem. If -boot is specified what
device are you going to boot from?

> diff --git a/hw/spapr.c b/hw/spapr.c
> index e6bf522..673bcc8 100644
> --- a/hw/spapr.c
> +++ b/hw/spapr.c
> @@ -284,7 +284,8 @@ static void *spapr_create_fdt_skel(const char
> *cpu_model,
> 
>          _FDT((fdt_property(fdt, "qemu,boot-kernel", &kprop,
> sizeof(kprop))));
>      }
> -    _FDT((fdt_property_string(fdt, "qemu,boot-device", boot_device)));
> +    if (!default_boot_order)
> +        _FDT((fdt_property_string(fdt, "qemu,boot-device", boot_device)));
>      _FDT((fdt_property_cell(fdt, "qemu,graphic-width", graphic_width)));
>      _FDT((fdt_property_cell(fdt, "qemu,graphic-height", graphic_height)));
>      _FDT((fdt_property_cell(fdt, "qemu,graphic-depth", graphic_depth)));
> diff --git a/sysemu.h b/sysemu.h
> index 65552ac..f0822b4 100644
> --- a/sysemu.h
> +++ b/sysemu.h
> @@ -129,6 +129,7 @@ extern int no_shutdown;
>  extern int semihosting_enabled;
>  extern int old_param;
>  extern int boot_menu;
> +extern int default_boot_order;
>  extern uint8_t *boot_splash_filedata;
>  extern int boot_splash_filedata_size;
>  extern uint8_t qemu_extra_params_fw[2];
> diff --git a/vl.c b/vl.c
> index 48049ef..bf369e6 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -230,6 +230,7 @@ int ctrl_grab = 0;
>  unsigned int nb_prom_envs = 0;
>  const char *prom_envs[MAX_PROM_ENVS];
>  int boot_menu;
> +int default_boot_order = 1;
>  uint8_t *boot_splash_filedata;
>  int boot_splash_filedata_size;
>  uint8_t qemu_extra_params_fw[2];
> @@ -2668,6 +2669,7 @@ int main(int argc, char **argv, char **envp)
>                          qemu_opts_parse(qemu_find_opts("boot-opts"),
>                                          optarg, 0);
>                      }
> +                    default_boot_order = 0;
>                  }
>                  break;
>              case QEMU_OPTION_fda:
> 
> 
> Comments welcome.
> 
> >>>However if we make the nvram override qemu, then it's trickier to
> >>>force-boot from, let's say, a rescue CD. The user would have to stop the
> >>>SLOF boot process by pressing a key then manually type something like
> >>>"boot cdrom".
> >>>
> >>>Maybe the right approach is "in between", and is that the primary driver
> >>>is the -boot argument. For each entry in the boot list, if it's "c", use
> >>>the configured boot-device or fallback to the automatic guess SLOF tries
> >>>to do today in absence of a boot-device. If it's "d" or "n" force it
> >>>respectively to cdrom or network...
> >>>
> >>>I think there is no perfect solution here. What do you guys think is the
> >>>less user unfriendly ?
> >>
> >>I think the command line should override anything user specified. So basically:
> >>
> >>   * user defined -boot option (or bootindex magic from Gleb)
> >>   * nvram
> >>   * fallback to default
> >>
> >>>Eventually we should try to implement some sort of interactive boot
> >>>device selection in SLOF, such as SMS does on pseries, but that will
> >>>take a bit of time.
> >>
> >>That would be en par with the bootmenu on x86 :). Please check out how x86 models these things. It could sure be interesting for pseries.
> >>
> >>
> >>Alex
> >
> >--
> >			Gleb.
> >
> >
> Regards,
> Avik

--
			Gleb.

Re: [Qemu-devel] [Qemu-ppc] Qemu boot device precedence over nvram boot-device setting

[Avik Sil]

On 10/04/2012 04:52 PM, Gleb Natapov 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"
>>
>> Now converting/translating this to OF device path is going to be
>> much trickier and might not be proper. So I propose a simple
>> solution by introducing a global flag that checks if explicit -boot
>> parameter is provided or not. The presence of this parameter is
>> verified in SLOF firmware. The flag had to be introduced as
>> boot_devices defaults to "cad" instead of null and passed to
>> machine->init().
>>
> So you want to hack around the problem. If -boot is specified what
> device are you going to boot from?

It is going to boot from the device specified in -boot as 
default_boot_order is set to 0 in that case.

Regards,
Avik

Re: [Qemu-devel] [Qemu-ppc] Qemu boot device precedence over nvram boot-device setting

[Alexander Graf]

On 04.10.2012, at 13:29, Avik Sil wrote:

> On 10/04/2012 04:52 PM, Gleb Natapov 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"
>>> 
>>> Now converting/translating this to OF device path is going to be
>>> much trickier and might not be proper. So I propose a simple
>>> solution by introducing a global flag that checks if explicit -boot
>>> parameter is provided or not. The presence of this parameter is
>>> verified in SLOF firmware. The flag had to be introduced as
>>> boot_devices defaults to "cad" instead of null and passed to
>>> machine->init().
>>> 
>> So you want to hack around the problem. If -boot is specified what
>> device are you going to boot from?
> 
> It is going to boot from the device specified in -boot as default_boot_order is set to 0 in that case.

Imagine you have 2 controllers:

  * vio
  * virtio

and you specify -boot c. Which device are you going to boot from?


Alex

Re: [Qemu-devel] [Qemu-ppc] Qemu boot device precedence over nvram boot-device setting

[Avik Sil]

>>>> 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"
>>>>
>>>> Now converting/translating this to OF device path is going to be
>>>> much trickier and might not be proper. So I propose a simple
>>>> solution by introducing a global flag that checks if explicit -boot
>>>> parameter is provided or not. The presence of this parameter is
>>>> verified in SLOF firmware. The flag had to be introduced as
>>>> boot_devices defaults to "cad" instead of null and passed to
>>>> machine->init().
>>>>
>>> So you want to hack around the problem. If -boot is specified what
>>> device are you going to boot from?
>>
>> It is going to boot from the device specified in -boot as default_boot_order is set to 0 in that case.
>
> Imagine you have 2 controllers:
>
>    * vio
>    * virtio
>
> and you specify -boot c. Which device are you going to boot from?

Currently, by default SLOF boots from the first disk it discovers in the 
device tree.

Regards,
Avik

>
>
> Alex
>
>

Re: [Qemu-devel] [Qemu-ppc] Qemu boot device precedence over nvram boot-device setting

[Alexander Graf]

On 04.10.2012, at 14:18, Avik Sil wrote:

>>>>> 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"
>>>>> 
>>>>> Now converting/translating this to OF device path is going to be
>>>>> much trickier and might not be proper. So I propose a simple
>>>>> solution by introducing a global flag that checks if explicit -boot
>>>>> parameter is provided or not. The presence of this parameter is
>>>>> verified in SLOF firmware. The flag had to be introduced as
>>>>> boot_devices defaults to "cad" instead of null and passed to
>>>>> machine->init().
>>>>> 
>>>> So you want to hack around the problem. If -boot is specified what
>>>> device are you going to boot from?
>>> 
>>> It is going to boot from the device specified in -boot as default_boot_order is set to 0 in that case.
>> 
>> Imagine you have 2 controllers:
>> 
>>   * vio
>>   * virtio
>> 
>> and you specify -boot c. Which device are you going to boot from?
> 
> Currently, by default SLOF boots from the first disk it discovers in the device tree.

So you want to replace one broken scheme with another broken scheme? :)


Alex

Re: [Qemu-devel] [Qemu-ppc] Qemu boot device precedence over nvram boot-device setting

[Avik Sil]

>>>>> So you want to hack around the problem. If -boot is specified what
>>>>> device are you going to boot from?
>>>>
>>>> It is going to boot from the device specified in -boot as default_boot_order is set to 0 in that case.
>>>
>>> Imagine you have 2 controllers:
>>>
>>>    * vio
>>>    * virtio
>>>
>>> and you specify -boot c. Which device are you going to boot from?
>>
>> Currently, by default SLOF boots from the first disk it discovers in the device tree.
>
> So you want to replace one broken scheme with another broken scheme? :)

Ha ha, actually we hit this issue in some different context with respect 
to nvram boot-device which I mentioned in [1]. The patch is a workaround 
for that issue only.

Regards,
Avik

>
>
> Alex
>
>
>
[1] http://lists.nongnu.org/archive/html/qemu-ppc/2012-10/msg00020.html

Re: [Qemu-devel] [Qemu-ppc] Qemu boot device precedence over nvram boot-device setting

[Alexander Graf]

On 04.10.2012, at 14:35, Avik Sil wrote:

>>>>>> So you want to hack around the problem. If -boot is specified what
>>>>>> device are you going to boot from?
>>>>> 
>>>>> It is going to boot from the device specified in -boot as default_boot_order is set to 0 in that case.
>>>> 
>>>> Imagine you have 2 controllers:
>>>> 
>>>>   * vio
>>>>   * virtio
>>>> 
>>>> and you specify -boot c. Which device are you going to boot from?
>>> 
>>> Currently, by default SLOF boots from the first disk it discovers in the device tree.
>> 
>> So you want to replace one broken scheme with another broken scheme? :)
> 
> Ha ha, actually we hit this issue in some different context with respect to nvram boot-device which I mentioned in [1]. The patch is a workaround for that issue only.

Seriously, just ignore -boot for now. It'd be a lot more useful to get bootindex working.


Alex

Re: [Qemu-devel] [Qemu-ppc] Qemu boot device precedence over nvram boot-device setting

[Gleb Natapov]

On Thu, Oct 04, 2012 at 02:37:22PM +0200, Alexander Graf wrote:
> 
> On 04.10.2012, at 14:35, Avik Sil wrote:
> 
> >>>>>> So you want to hack around the problem. If -boot is specified what
> >>>>>> device are you going to boot from?
> >>>>> 
> >>>>> It is going to boot from the device specified in -boot as default_boot_order is set to 0 in that case.
> >>>> 
> >>>> Imagine you have 2 controllers:
> >>>> 
> >>>>   * vio
> >>>>   * virtio
> >>>> 
> >>>> and you specify -boot c. Which device are you going to boot from?
> >>> 
> >>> Currently, by default SLOF boots from the first disk it discovers in the device tree.
> >> 
> >> So you want to replace one broken scheme with another broken scheme? :)
> > 
> > Ha ha, actually we hit this issue in some different context with respect to nvram boot-device which I mentioned in [1]. The patch is a workaround for that issue only.
> 
> Seriously, just ignore -boot for now. It'd be a lot more useful to get bootindex working.
> 
+1

--
			Gleb.

Re: [Qemu-devel] [Qemu-ppc] Qemu boot device precedence over nvram boot-device setting

[Nikunj A Dadhania]

On Thu, 4 Oct 2012 14:37:22 +0200, Alexander Graf <agraf@suse.de> wrote:
> 
> >>>> Imagine you have 2 controllers:
> >>>> 
> >>>>   * vio
> >>>>   * virtio
> >>>> 
> >>>> and you specify -boot c. Which device are you going to boot from?
> >>> 
> >>> Currently, by default SLOF boots from the first disk it discovers in the device tree.
> >> 
> >> So you want to replace one broken scheme with another broken scheme? :)
> > 
> > Ha ha, actually we hit this issue in some different context with respect to nvram boot-device which I mentioned in [1]. The patch is a workaround for that issue only.
> 
> Seriously, just ignore -boot for now. It'd be a lot more useful to get bootindex working.

I understand your point here. Adding bootindex feature is desirable, I
agree to that. While, in the particular use case, we just need to know
that -boot was not provided (and some vague default "cad" is provided,
which can actually be a user passed parameter as well) and rest can be
handled by the firmware.

Regards,
Nikunj

Re: [Qemu-devel] [Qemu-ppc] Qemu boot device precedence over nvram boot-device setting

[Gleb Natapov]

On Thu, Oct 04, 2012 at 04:59:27PM +0530, Avik Sil wrote:
> On 10/04/2012 04:52 PM, Gleb Natapov 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"
> >>
> >>Now converting/translating this to OF device path is going to be
> >>much trickier and might not be proper. So I propose a simple
> >>solution by introducing a global flag that checks if explicit -boot
> >>parameter is provided or not. The presence of this parameter is
> >>verified in SLOF firmware. The flag had to be introduced as
> >>boot_devices defaults to "cad" instead of null and passed to
> >>machine->init().
> >>
> >So you want to hack around the problem. If -boot is specified what
> >device are you going to boot from?
> 
> It is going to boot from the device specified in -boot as
> default_boot_order is set to 0 in that case.
> 
-boot has not enough verbosity to tell the device to boot from if you
have more than one device of each type. What are you going to boot from
if you have two disks, two NICs, etc?

--
			Gleb.

Re: [Qemu-devel] [Qemu-ppc] Qemu boot device precedence over nvram boot-device setting

[Avik Sil]

>>>> 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"
>>>>
>>>> Now converting/translating this to OF device path is going to be
>>>> much trickier and might not be proper. So I propose a simple
>>>> solution by introducing a global flag that checks if explicit -boot
>>>> parameter is provided or not. The presence of this parameter is
>>>> verified in SLOF firmware. The flag had to be introduced as
>>>> boot_devices defaults to "cad" instead of null and passed to
>>>> machine->init().
>>>>
>>> So you want to hack around the problem. If -boot is specified what
>>> device are you going to boot from?
>>
>> It is going to boot from the device specified in -boot as
>> default_boot_order is set to 0 in that case.
>>
> -boot has not enough verbosity to tell the device to boot from if you
> have more than one device of each type. What are you going to boot from
> if you have two disks, two NICs, etc?

Yes, -boot has this limitation and -boot is what we are currently using. 
We are extending this using the nvram boot-device property. With the 
nvram driver in place, we would be booting from boot-device. We also 
need a way from qemu to override this, where we hit this issue of the 
default boot device. And currently SLOF boots from the first disk/cdrom 
it discovers in device tree in case there are multiple disks or cdroms.

Regards,
Avik

>
> --
> 			Gleb.
>
>
>

Re: [Qemu-devel] [Qemu-ppc] Qemu boot device precedence over nvram boot-device setting

[David Gibson]

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?

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?

> Now converting/translating this to OF device path is going to be
> much trickier and might not be proper. So I propose a simple
> solution by introducing a global flag that checks if explicit -boot
> parameter is provided or not. The presence of this parameter is
> verified in SLOF firmware. The flag had to be introduced as
> boot_devices defaults to "cad" instead of null and passed to
> machine->init().

So, personally, I think this is quite a reasonable interim measure
until we figure out how to do bootindex.  I will fold it into our
internal tree for now, even if the qemu people are going to bitch and
moan about its imperfections.  Can you send me a clean copy with
commit message, please?

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

Re: [Qemu-devel] [Qemu-ppc] Qemu boot device precedence over nvram boot-device setting

[Alexander Graf]

On 05.10.2012, at 02:34, David Gibson 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?
> 
> 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...

Well. You can track it down to the device level and you know the drive index. Maybe you could be clever if you had a device property that contains the drive index and boot index to it?

> 
> 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?

Yes, that sounds exactly right :).

> 
>> Now converting/translating this to OF device path is going to be
>> much trickier and might not be proper. So I propose a simple
>> solution by introducing a global flag that checks if explicit -boot
>> parameter is provided or not. The presence of this parameter is
>> verified in SLOF firmware. The flag had to be introduced as
>> boot_devices defaults to "cad" instead of null and passed to
>> machine->init().
> 
> So, personally, I think this is quite a reasonable interim measure
> until we figure out how to do bootindex.  I will fold it into our
> internal tree for now, even if the qemu people are going to bitch and
> moan about its imperfections.  Can you send me a clean copy with
> commit message, please?

I actually don't remember having seen a patch at all :).


Alex

Re: [Qemu-devel] [Qemu-ppc] Qemu boot device precedence over nvram boot-device setting

[David Gibson]

On Fri, Oct 05, 2012 at 02:43:31AM +0200, Alexander Graf wrote:
> 
> On 05.10.2012, at 02:34, David Gibson 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?
> > 
> > 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...
> 
> Well. You can track it down to the device level and you know the
> drive index. Maybe you could be clever if you had a device property
> that contains the drive index and boot index to it?

Yeah, I guess.  Working that out is a lot more complex than cases
where we have a one-to-one correspondance between qdevs and device
tree nodes.

> > 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?
> 
> Yes, that sounds exactly right :).
> 
> >> Now converting/translating this to OF device path is going to be
> >> much trickier and might not be proper. So I propose a simple
> >> solution by introducing a global flag that checks if explicit -boot
> >> parameter is provided or not. The presence of this parameter is
> >> verified in SLOF firmware. The flag had to be introduced as
> >> boot_devices defaults to "cad" instead of null and passed to
> >> machine->init().
> > 
> > So, personally, I think this is quite a reasonable interim measure
> > until we figure out how to do bootindex.  I will fold it into our
> > internal tree for now, even if the qemu people are going to bitch and
> > moan about its imperfections.  Can you send me a clean copy with
> > commit message, please?
> 
> I actually don't remember having seen a patch at all :).

Um.. it was immediately below that in the original message.

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

Re: [Qemu-devel] [Qemu-ppc] Qemu boot device precedence over nvram boot-device setting

[Benjamin Herrenschmidt]

On Fri, 2012-10-05 at 02:43 +0200, Alexander Graf wrote:
> > 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...
> 
> Well. You can track it down to the device level and you know the drive
> index. Maybe you could be clever if you had a device property that
> contains the drive index and boot index to it?

You can but it's hard... eventually we'll do it but it will take some
time. In the meantime, a patch allowing us know whether -boot was
specified at all or not would be handy to make things work as expected
in the most common cases.

Avik & Nikunj are going to send one if not already...

Cheers,
Ben.

Re: [Qemu-devel] [Qemu-ppc] Qemu boot device precedence over nvram boot-device setting

[Alexander Graf]

On 05.10.2012, at 11:12, Benjamin Herrenschmidt <benh@au1.ibm.com> wrote:

> On Fri, 2012-10-05 at 02:43 +0200, Alexander Graf wrote:
>>> 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...
>> 
>> Well. You can track it down to the device level and you know the drive
>> index. Maybe you could be clever if you had a device property that
>> contains the drive index and boot index to it?
> 
> You can but it's hard... eventually we'll do it but it will take some
> time. In the meantime, a patch allowing us know whether -boot was
> specified at all or not would be handy to make things work as expected
> in the most common cases.

Sure, no objections there :). See my reply on the patch.

Alex

> 
> Avik & Nikunj are going to send one if not already...
> 
> Cheers,
> Ben.
> 
> 

Re: [Qemu-devel] [Qemu-ppc] Qemu boot device precedence over nvram boot-device setting

[Nikunj A Dadhania]

On Fri, 5 Oct 2012 10:34:16 +1000, David Gibson <dwg@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

Re: [Qemu-devel] [Qemu-ppc] Qemu boot device precedence over nvram boot-device setting

[Avik Sil]

>>> 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.

Perhaps the default boot order "disk cdrom" should be taken care of if 
none of bootindex, -boot and nvram boot-device is provided.
>
> Regards
> Nikunj
>

Regards,
Avik