Booting an Ultra sparc with 2.6

Booting an Ultra sparc with 2.6

[Luis R. Rodriguez]

Hi all,

I've been trying to boot 2.6 on an ultra sparc and just can't seem to
get it to work. I've read in some outdated docs the kernel must be <
~3MB, and that compression is sometimes flaky. Is any of this
information correct?

Thanks,

	Luis

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Re: Booting an Ultra sparc with 2.6

[Clemens Buchacher]

On Mon, Sep 13, 2004 at 10:38:11AM -0400, Luis R. Rodriguez wrote:
> [...] I've read in some outdated docs the kernel must be <
> ~3MB, and that compression is sometimes flaky. Is any of this
> information correct?

The UltraLinux FAQ claims it must be smaller ~2.6 MB, but I cannot tell
if this information is up-to-date either.

http://www.ultralinux.org/faq.html#q_4_10

Clemens

Re: Booting an Ultra sparc with 2.6

[Luis R. Rodriguez]

On Tue, Sep 14, 2004 at 07:22:29PM +0200, Clemens Buchacher wrote:
> On Mon, Sep 13, 2004 at 10:38:11AM -0400, Luis R. Rodriguez wrote:
> > [...] I've read in some outdated docs the kernel must be <
> > ~3MB, and that compression is sometimes flaky. Is any of this
> > information correct?
> 
> The UltraLinux FAQ claims it must be smaller ~2.6 MB, but I cannot tell
> if this information is up-to-date either.
> 
> http://www.ultralinux.org/faq.html#q_4_10
> 
> Clemens

Thank Clemens, yes that is where I had read it. That documentation
seemed horribly out of date though. I also would like an explanation as
to this 2.6 MB kernel size limitation.

	Luis

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Re: Booting an Ultra sparc with 2.6

[David S. Miller]

On Mon, 13 Sep 2004 18:21:02 -0400
mcgrof@studorgs.rutgers.edu (Luis R. Rodriguez) wrote:

> I also would like an explanation as
> to this 2.6 MB kernel size limitation.

It was a bootloader limitation which is fixed in current
SILO bootloader versions.

Re: Booting an Ultra sparc with 2.6

[Luis R. Rodriguez]

On Mon, Sep 13, 2004 at 03:38:45PM -0700, David S. Miller wrote:
> On Mon, 13 Sep 2004 18:21:02 -0400
> mcgrof@studorgs.rutgers.edu (Luis R. Rodriguez) wrote:
> 
> > I also would like an explanation as
> > to this 2.6 MB kernel size limitation.
> 
> It was a bootloader limitation which is fixed in current
> SILO bootloader versions.

Thanks Dave,

So I should be able to boot a large vmlinux now ? How about compression,
is handling compressed kernels still an issue ? Should I be trying to
boot vmlimux or my own created gzip -9 vmlinux ?

Also why is the compressed kernel not made at `make` time and not put
in:

arch/sparc64/boot/

?

And is there any use to the image built as a result of `make image`? I
know its smaller, but what exactly goes into/out this kernel to make
it smaller?

	Luis

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Re: Booting an Ultra sparc with 2.6

[David S. Miller]

On Mon, 13 Sep 2004 18:47:13 -0400
mcgrof@studorgs.rutgers.edu (Luis R. Rodriguez) wrote:

> So I should be able to boot a large vmlinux now ? How about compression,
> is handling compressed kernels still an issue ? Should I be trying to
> boot vmlimux or my own created gzip -9 vmlinux ?

It works, but you needn't do that.

> And is there any use to the image built as a result of `make image`? I
> know its smaller, but what exactly goes into/out this kernel to make
> it smaller?

The symbol table is stripped to the bare minimum.

Re: Booting an Ultra sparc with 2.6

[Luis R. Rodriguez]

On Mon, Sep 13, 2004 at 03:49:40PM -0700, David S. Miller wrote:
> On Mon, 13 Sep 2004 18:47:13 -0400
> mcgrof@studorgs.rutgers.edu (Luis R. Rodriguez) wrote:
> 
> > So I should be able to boot a large vmlinux now ? How about compression,
> > is handling compressed kernels still an issue ? Should I be trying to
> > boot vmlimux or my own created gzip -9 vmlinux ?
> 
> It works, but you needn't do that.

Great, thanks. 

> > And is there any use to the image built as a result of `make image`? I
> > know its smaller, but what exactly goes into/out this kernel to make
> > it smaller?
> 
> The symbol table is stripped to the bare minimum.

Is the kernel fully functional like this? What's the downside to this?

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Re: Booting an Ultra sparc with 2.6

[David S. Miller]

On Mon, 13 Sep 2004 19:20:19 -0400
mcgrof@studorgs.rutgers.edu (Luis R. Rodriguez) wrote:

> > > And is there any use to the image built as a result of `make image`? I
> > > know its smaller, but what exactly goes into/out this kernel to make
> > > it smaller?
> > 
> > The symbol table is stripped to the bare minimum.
> 
> Is the kernel fully functional like this?

Yes, fully.

> What's the downside to this?

No symbols means it's harder to examine the kernel image
using tools like 'gdb' and 'nm', but System.map still contains
the full symbol table information so even this point is moot.

Re: Booting an Ultra sparc with 2.6

[Luis R. Rodriguez]

[-- Attachment #1: Type: text/plain, Size: 808 bytes --]

On Mon, Sep 13, 2004 at 03:38:45PM -0700, David S. Miller wrote:
> On Mon, 13 Sep 2004 18:21:02 -0400
> mcgrof@studorgs.rutgers.edu (Luis R. Rodriguez) wrote:
> 
> > I also would like an explanation as
> > to this 2.6 MB kernel size limitation.
> 
> It was a bootloader limitation which is fixed in current
> SILO bootloader versions.

OK -- I have silo 1.4.8 and I can't still boot into a 2.6 kernel. I've
tried many things:

a. boot into vmlinux (48MB)
	result: image too large
b. boot into vmlinuz (24MB)
	result: image too large
c. boot into image (5.1MB)
	result: it hangs on trying to boot 2.6.9

and no luck. What version of silo fixed this kernel size limitation?
Also any suggestions?

	Luis

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Re: Booting an Ultra sparc with 2.6

[Luis R. Rodriguez]

On Mon, Oct 25, 2004 at 08:32:12PM -0400, Luis R. Rodriguez wrote:
> On Mon, Sep 13, 2004 at 03:38:45PM -0700, David S. Miller wrote:
> > On Mon, 13 Sep 2004 18:21:02 -0400
> > mcgrof@studorgs.rutgers.edu (Luis R. Rodriguez) wrote:
> > 
> > > I also would like an explanation as
> > > to this 2.6 MB kernel size limitation.
> > 
> > It was a bootloader limitation which is fixed in current
> > SILO bootloader versions.
> 
> OK -- I have silo 1.4.8 and I can't still boot into a 2.6 kernel. I've
> tried many things:
> 
> a. boot into vmlinux (48MB)
> 	result: image too large
> b. boot into vmlinuz (24MB)
> 	result: image too large
> c. boot into image (5.1MB)
> 	result: it hangs on trying to boot 2.6.9
> 
> and no luck. What version of silo fixed this kernel size limitation?
> Also any suggestions?
> 

Oh and this is for a sparc64 (Ultra 5).

	Luis

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Re: Booting an Ultra sparc with 2.6

[Luis R. Rodriguez]

On Mon, Oct 25, 2004 at 08:38:06PM -0400, Luis R. Rodriguez wrote:
> On Mon, Oct 25, 2004 at 08:32:12PM -0400, Luis R. Rodriguez wrote:
> > On Mon, Sep 13, 2004 at 03:38:45PM -0700, David S. Miller wrote:
> > > On Mon, 13 Sep 2004 18:21:02 -0400
> > > mcgrof@studorgs.rutgers.edu (Luis R. Rodriguez) wrote:
> > > 
> > > > I also would like an explanation as
> > > > to this 2.6 MB kernel size limitation.
> > > 
> > > It was a bootloader limitation which is fixed in current
> > > SILO bootloader versions.
> > 
> > OK -- I have silo 1.4.8 and I can't still boot into a 2.6 kernel. I've
> > tried many things:
> > 
> > a. boot into vmlinux (48MB)
> > 	result: image too large
> > b. boot into vmlinuz (24MB)
> > 	result: image too large
> > c. boot into image (5.1MB)
> > 	result: it hangs on trying to boot 2.6.9
> > 
> > and no luck. What version of silo fixed this kernel size limitation?
> > Also any suggestions?
> > 
> 
> Oh and this is for a sparc64 (Ultra 5).

And if this helps too:

silo -v # To get PROM version
IEEE 1275

	Luis

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Re: Booting an Ultra sparc with 2.6

[David S. Miller]

On Mon, 25 Oct 2004 20:32:12 -0400
mcgrof@studorgs.rutgers.edu (Luis R. Rodriguez) wrote:

> a. boot into vmlinux (48MB)
> 	result: image too large

Please, why in the world do you need a 48MB kernel
image?

Re: Booting an Ultra sparc with 2.6

[Luis R. Rodriguez]

On Mon, Oct 25, 2004 at 07:53:28PM -0700, David S. Miller wrote:
> On Mon, 25 Oct 2004 20:32:12 -0400
> mcgrof@studorgs.rutgers.edu (Luis R. Rodriguez) wrote:
> 
> > a. boot into vmlinux (48MB)
> > 	result: image too large
> 
> Please, why in the world do you need a 48MB kernel
> image?

Hey -- I can reduce the size, sure but that is besides the point. I want
to know the details of the size limitations of the kernel image for
sparc64. You told me last that there was no size limitations, that this
was fixed in the latest version of silo.

	Luis

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Re: Booting an Ultra sparc with 2.6

[Andrew Gaffney]

Luis R. Rodriguez wrote:
> On Mon, Oct 25, 2004 at 07:53:28PM -0700, David S. Miller wrote:
> 
>>On Mon, 25 Oct 2004 20:32:12 -0400
>>mcgrof@studorgs.rutgers.edu (Luis R. Rodriguez) wrote:
>>
>>
>>>a. boot into vmlinux (48MB)
>>>	result: image too large
>>
>>Please, why in the world do you need a 48MB kernel
>>image?
> 
> Hey -- I can reduce the size, sure but that is besides the point. I want
> to know the details of the size limitations of the kernel image for
> sparc64. You told me last that there was no size limitations, that this
> was fixed in the latest version of silo.

It is something closer to "no unreasonable size limit". I believe the limit is 
7.5MB, which should more than enough for *any* kernel you'd ever need to compile.

-- 
Andrew Gaffney
Network Administrator
Skyline Aeronautics, LLC.
636-357-1548

Re: Booting an Ultra sparc with 2.6

[Luis R. Rodriguez]

On Tue, Oct 26, 2004 at 01:16:04AM -0500, Andrew Gaffney wrote:
> Luis R. Rodriguez wrote:
> >On Mon, Oct 25, 2004 at 07:53:28PM -0700, David S. Miller wrote:
> >
> >>On Mon, 25 Oct 2004 20:32:12 -0400
> >>mcgrof@studorgs.rutgers.edu (Luis R. Rodriguez) wrote:
> >>
> >>
> >>>a. boot into vmlinux (48MB)
> >>>	result: image too large
> >>
> >>Please, why in the world do you need a 48MB kernel
> >>image?
> >
> >Hey -- I can reduce the size, sure but that is besides the point. I want
> >to know the details of the size limitations of the kernel image for
> >sparc64. You told me last that there was no size limitations, that this
> >was fixed in the latest version of silo.
> 
> It is something closer to "no unreasonable size limit". I believe the limit 
> is 7.5MB, which should more than enough for *any* kernel you'd ever need to 
> compile.

Andrew, thanks -- and *that* is what I needed. I'll try to reduce my
kernel size now. I swear, I have been trying to limit it as much as I
can already I guess I'll have to try harder :)

Anyone know *why* this 7.5MB limit exists?

	Luis

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Re: Booting an Ultra sparc with 2.6

[Andrew Gaffney]

Luis R. Rodriguez wrote:
> On Tue, Oct 26, 2004 at 01:16:04AM -0500, Andrew Gaffney wrote:
> 
>>Luis R. Rodriguez wrote:
>>
>>>On Mon, Oct 25, 2004 at 07:53:28PM -0700, David S. Miller wrote:
>>>
>>>
>>>>On Mon, 25 Oct 2004 20:32:12 -0400
>>>>mcgrof@studorgs.rutgers.edu (Luis R. Rodriguez) wrote:
>>>>
>>>>>a. boot into vmlinux (48MB)
>>>>>	result: image too large
>>>>
>>>>Please, why in the world do you need a 48MB kernel
>>>>image?
>>>
>>>Hey -- I can reduce the size, sure but that is besides the point. I want
>>>to know the details of the size limitations of the kernel image for
>>>sparc64. You told me last that there was no size limitations, that this
>>>was fixed in the latest version of silo.
>>
>>It is something closer to "no unreasonable size limit". I believe the limit 
>>is 7.5MB, which should more than enough for *any* kernel you'd ever need to 
>>compile.
> 
> Andrew, thanks -- and *that* is what I needed. I'll try to reduce my
> kernel size now. I swear, I have been trying to limit it as much as I
> can already I guess I'll have to try harder :)
> 
> Anyone know *why* this 7.5MB limit exists?

So people don't try to boot 48MB kernels? :P

-- 
Andrew Gaffney
Network Administrator
Skyline Aeronautics, LLC.
636-357-1548

Re: Booting an Ultra sparc with 2.6

[David S. Miller]

On Tue, 26 Oct 2004 02:11:28 -0400
mcgrof@studorgs.rutgers.edu (Luis R. Rodriguez) wrote:

> Hey -- I can reduce the size, sure but that is besides the point. I want
> to know the details of the size limitations of the kernel image for
> sparc64. You told me last that there was no size limitations, that this
> was fixed in the latest version of silo.

It should be ~8MB these days.

I bet if you just use arch/sparc64/defconfig as your kernel
config the resulting image will work if you have working
compiler tools.

I use just about every 2.6.x release on my Ultra60, SunBlade100
and my SunBlade1000.

Re: Booting an Ultra sparc with 2.6

[David S. Miller]

On Tue, 26 Oct 2004 02:28:19 -0400
mcgrof@studorgs.rutgers.edu (Luis R. Rodriguez) wrote:

> Anyone know *why* this 7.5MB limit exists?

Because we lock the kernel image into the TLB, we use
4MB TLB entries (the largest UltraSPARC currently supports)
and locking 2 entries is what we limit things to.

Use modules dude.  Also, strip all debugging information
and unnecessary symbol table entries from your kernel
as well.  "make image" helps with this, use the
arch/sparc64/boot/image file that rule creates not
the top-level vmlinux file.

Re: Booting an Ultra sparc with 2.6

[Luis R. Rodriguez]

On Mon, Oct 25, 2004 at 11:46:30PM -0700, David S. Miller wrote:
> On Tue, 26 Oct 2004 02:11:28 -0400
> mcgrof@studorgs.rutgers.edu (Luis R. Rodriguez) wrote:
> 
> > Hey -- I can reduce the size, sure but that is besides the point. I want
> > to know the details of the size limitations of the kernel image for
> > sparc64. You told me last that there was no size limitations, that this
> > was fixed in the latest version of silo.
> 
> It should be ~8MB these days.
> 
> I bet if you just use arch/sparc64/defconfig as your kernel
> config the resulting image will work if you have working
> compiler tools.

Ah nice, I didn't know about that file. Will try it when I get home,
thanks :)

> I use just about every 2.6.x release on my Ultra60, SunBlade100
> and my SunBlade1000.

Cool, good to know it does indeed work :)

	Luis

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Re: Booting an Ultra sparc with 2.6

[Luis R. Rodriguez]

On Mon, Oct 25, 2004 at 11:48:13PM -0700, David S. Miller wrote:
> On Tue, 26 Oct 2004 02:28:19 -0400
> mcgrof@studorgs.rutgers.edu (Luis R. Rodriguez) wrote:
> 
> > Anyone know *why* this 7.5MB limit exists?
> 
> Because we lock the kernel image into the TLB, we use
> 4MB TLB entries (the largest UltraSPARC currently supports)
> and locking 2 entries is what we limit things to.

Interesting! What is a TLB entry though -- a set range of TLB address
space? If the UltraSPARC has a max size 4MB TLB, how can we lock two 4MB TLBs
entries?

> Use modules dude. 

I do man, for some reason I just keep getting it bloated. I'll use that
defconfig file now though :)

> Also, strip all debugging information
> and unnecessary symbol table entries from your kernel
> as well.  

Well I'm using this as a dev box so I wan to keep this.

> "make image" helps with this, use the
> arch/sparc64/boot/image file that rule creates not
> the top-level vmlinux file.

I tried using that image file and the kernel would hang. Not sure why
:T.

	Luis

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Re: Booting an Ultra sparc with 2.6

[Adam Kropelin]

Luis R. Rodriguez wrote:
> On Mon, Oct 25, 2004 at 11:48:13PM -0700, David S. Miller wrote:
>> On Tue, 26 Oct 2004 02:28:19 -0400
>> mcgrof@studorgs.rutgers.edu (Luis R. Rodriguez) wrote:
>>
>>> Anyone know *why* this 7.5MB limit exists?
>>
>> Because we lock the kernel image into the TLB, we use
>> 4MB TLB entries (the largest UltraSPARC currently supports)
>> and locking 2 entries is what we limit things to.
>
> Interesting! What is a TLB entry though -- a set range of TLB address
> space? If the UltraSPARC has a max size 4MB TLB, how can we lock two
> 4MB TLBs entries?

Speaking for the general case, since I am not a sparc64 MMU guru: The TLB is 
a cache of virtual-to-physical address translations. A TLB holds multiple 
enties, each of which provides the translation for a particular region of 
address space. The size of the region being mapped is selected from among 
the set of possibilities offered by the hardware. What David is saying is 
that on sparc64 the largest choice is 4 MB and since, by convention, 2 TLB 
entries are reserved for the kernel image that means a max kernel size of 8 
MB.

--Adam

Re: Booting an Ultra sparc with 2.6

[Luis R. Rodriguez]

On Wed, Oct 27, 2004 at 06:58:15PM -0400, Adam Kropelin wrote:
> Luis R. Rodriguez wrote:
> >On Mon, Oct 25, 2004 at 11:48:13PM -0700, David S. Miller wrote:
> >>On Tue, 26 Oct 2004 02:28:19 -0400
> >>mcgrof@studorgs.rutgers.edu (Luis R. Rodriguez) wrote:
> >>
> >>>Anyone know *why* this 7.5MB limit exists?
> >>
> >>Because we lock the kernel image into the TLB, we use
> >>4MB TLB entries (the largest UltraSPARC currently supports)
> >>and locking 2 entries is what we limit things to.
> >
> >Interesting! What is a TLB entry though -- a set range of TLB address
> >space? If the UltraSPARC has a max size 4MB TLB, how can we lock two
> >4MB TLBs entries?
> 
> Speaking for the general case, since I am not a sparc64 MMU guru: The TLB 
> is a cache of virtual-to-physical address translations. A TLB holds 
> multiple enties, each of which provides the translation for a particular 
> region of address space. The size of the region being mapped is selected 
> from among the set of possibilities offered by the hardware. What David is 
> saying is that on sparc64 the largest choice is 4 MB and since, by 
> convention, 2 TLB entries are reserved for the kernel image that means a 
> max kernel size of 8 MB.

Adam this is great thanks. So -- an entry is just an address space
defined by:

a. Starting memory address
b. Size (availalble options are hardware-specific)

Is this correct?

Also, who is in charge reserving these these 2 TLB entries ? silo?
How big is sparc64's TLB? This is a bit OT but I read something that 
said x86 processors have a really small TLB. What do we do on x86 to
boot the kernl? How about other procs?

Also, anyoe here use grub for sparc? How's that going?

	Luis

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Re: Booting an Ultra sparc with 2.6

[David S. Miller]

On Wed, 27 Oct 2004 19:57:39 -0400
mcgrof@studorgs.rutgers.edu (Luis R. Rodriguez) wrote:

> Also, who is in charge reserving these these 2 TLB entries ? silo?
> How big is sparc64's TLB? This is a bit OT but I read something that 
> said x86 processors have a really small TLB. What do we do on x86 to
> boot the kernl? How about other procs?

The kernel locks these two TLB entires into the MMU.  It only locks
one if the kernel image is 4MB or smaller.

We lock these entries into the TLB because the TLB is reloaded by
software trap handlers.  Therefore we have to at least lock enough
of the kernel image into the TLB such that the trap handler mappings
itself does not incur a TLB miss.

The x86 processor does TLB replacement in hardware, not software.
So something like this is not needed there.

The number of TLB entries varies by UltraSPARC, 64 in older chips
(pre ultrasparc-III) and 16 (of the kind that can be locked) in
ultrasparc-III and later.

Just make you silly kernel images smaller.  My arch/sparc64/boot/image
is typically 3.8MB or smaller.  Even if you want all that debugging
information in the kernel image (ie. building with "-g" in cflags or
whatever) you don't need all of that extra stuff in the kernel image
that is actually booted.  Copy over the vmlinux file with all the
stuff in it to some place where you can run gdb on it or whatever
it is you need the debugging info for, then use a seperate copy for
booting under /boot and strip the crap out of that file so that it
is as small as possible.