Bug#1106757: ppc64el Trixie: Need default 64KB page kernel or installer option

[Trupti]

On 2025-07-28 13:43, Trupti wrote:

On 2025-07-26 17:59, Steve McIntyre wrote:

On Sat, Jul 26, 2025 at 01:06:07PM +0100, Steve McIntyre wrote:

On Wed, Jul 23, 2025 at 08:12:08AM +0200, Cyril Brulebois wrote:

Pascal Hambourg  (2025-05-29):

   kibi@tokyo:~/debian-cd/debian-cd.git (kibi/easy)$ git diff
   diff --git a/tools/generate_di+k_list b/tools/generate_di+k_list
   index 2bee6440..9801b932 100755
   --- a/tools/generate_di+k_list
   +++ b/tools/generate_di+k_list
   @@ -305,6 +305,7 @@ grub-ieee1275
powerpc-utils
powerpc-ibm-utils
linux-image-powerpc64le
   +linux-image-powerpc64le-64k
#endif

#ifdef ARCH_alpha

This might push other packages out of the netinst though.

Cc-ing debian-cd@, who is responsible for installation images.


Sorry for the delayed response - catching up on sleep after debconf.

Yeah, that patch is the obvious thing here. On the ppc64el netinst I
think we have plenty of space.

I'll tah that now and trigger a test build.


That build completed ok, and the extra kernel is included. Trupti:
could you grab the latest faily netinst and see if that works better
for you now please?


Hello Steve,

Thank you so much for adding the extra kernel.

I will check with the new daily netinst image and let you know the
results as soon as possible.



Hello,

I tried installing Trixie using the Expert Install option with the 
latest daily netinst image, and I was able to select the 64K kernel 
right from the start of the installation. It's working now.


Thanks again for providing this option!

Best Regards
Trupti.

Bug#1106757: ppc64el Trixie: Need default 64KB page kernel or installer option

[Trupti]

On 2025-07-26 17:59, Steve McIntyre wrote:

On Sat, Jul 26, 2025 at 01:06:07PM +0100, Steve McIntyre wrote:

On Wed, Jul 23, 2025 at 08:12:08AM +0200, Cyril Brulebois wrote:

Pascal Hambourg  (2025-05-29):

   kibi@tokyo:~/debian-cd/debian-cd.git (kibi/easy)$ git diff
   diff --git a/tools/generate_di+k_list b/tools/generate_di+k_list
   index 2bee6440..9801b932 100755
   --- a/tools/generate_di+k_list
   +++ b/tools/generate_di+k_list
   @@ -305,6 +305,7 @@ grub-ieee1275
powerpc-utils
powerpc-ibm-utils
linux-image-powerpc64le
   +linux-image-powerpc64le-64k
#endif

#ifdef ARCH_alpha

This might push other packages out of the netinst though.

Cc-ing debian-cd@, who is responsible for installation images.


Sorry for the delayed response - catching up on sleep after debconf.

Yeah, that patch is the obvious thing here. On the ppc64el netinst I
think we have plenty of space.

I'll tah that now and trigger a test build.


That build completed ok, and the extra kernel is included. Trupti:
could you grab the latest faily netinst and see if that works better
for you now please?


Hello Steve,

Thank you so much for adding the extra kernel.

I will check with the new daily netinst image and let you know the 
results as soon as possible.


Best regards,
Trupti

Bug#1106757: ppc64el Trixie: Need default 64KB page kernel or installer option

[Steve McIntyre]

On Sat, Jul 26, 2025 at 01:06:07PM +0100, Steve McIntyre wrote:
>On Wed, Jul 23, 2025 at 08:12:08AM +0200, Cyril Brulebois wrote:
>>Pascal Hambourg  (2025-05-29):
>>
>>kibi@tokyo:~/debian-cd/debian-cd.git (kibi/easy)$ git diff
>>diff --git a/tools/generate_di+k_list b/tools/generate_di+k_list
>>index 2bee6440..9801b932 100755
>>--- a/tools/generate_di+k_list
>>+++ b/tools/generate_di+k_list
>>@@ -305,6 +305,7 @@ grub-ieee1275
>> powerpc-utils
>> powerpc-ibm-utils
>> linux-image-powerpc64le
>>+linux-image-powerpc64le-64k
>> #endif
>> 
>> #ifdef ARCH_alpha
>>
>>This might push other packages out of the netinst though.
>>
>>Cc-ing debian-cd@, who is responsible for installation images.
>
>Sorry for the delayed response - catching up on sleep after debconf.
>
>Yeah, that patch is the obvious thing here. On the ppc64el netinst I
>think we have plenty of space.
>
>I'll tah that now and trigger a test build.

That build completed ok, and the extra kernel is included. Trupti:
could you grab the latest faily netinst and see if that works better
for you now please?

-- 
Steve McIntyre, Cambridge, UK.st...@einval.com
Google-bait:   https://www.debian.org/CD/free-linux-cd
  Debian does NOT ship free CDs. Please do NOT contact the mailing
  lists asking us to send them to you.

Bug#1106757: ppc64el Trixie: Need default 64KB page kernel or installer option

[Steve McIntyre]

Hey folks,

On Wed, Jul 23, 2025 at 08:12:08AM +0200, Cyril Brulebois wrote:
>Pascal Hambourg  (2025-05-29):
>> (Removing kernel team)
>> 
>> On 29/05/2025 at 15:54, Cyril Brulebois wrote:
>> > Trupti  (2025-05-29):
>> > > 
>> > > Add a clear installer option to select a 64KB page kernel.
>> > 
>> > I believe this should be offered in expert mode, have you tried that?
>> 
>> AFAICS linux-image-powerpc64le-64k is not included in the DVD-1 image, so it
>> requires a network mirror. Same with linux-image-arm64-16k.
>
>I suppose something like this might do the trick?
>
>kibi@tokyo:~/debian-cd/debian-cd.git (kibi/easy)$ git diff
>diff --git a/tools/generate_di+k_list b/tools/generate_di+k_list
>index 2bee6440..9801b932 100755
>--- a/tools/generate_di+k_list
>+++ b/tools/generate_di+k_list
>@@ -305,6 +305,7 @@ grub-ieee1275
> powerpc-utils
> powerpc-ibm-utils
> linux-image-powerpc64le
>+linux-image-powerpc64le-64k
> #endif
> 
> #ifdef ARCH_alpha
>
>This might push other packages out of the netinst though.
>
>Cc-ing debian-cd@, who is responsible for installation images.

Sorry for the delayed response - catching up on sleep after debconf.

Yeah, that patch is the obvious thing here. On the ppc64el netinst I
think we have plenty of space.

I'll tah that now and trigger a test build.

-- 
Steve McIntyre, Cambridge, UK.st...@einval.com
"... the premise [is] that privacy is about hiding a wrong. It's not.
 Privacy is an inherent human right, and a requirement for maintaining
 the human condition with dignity and respect."
  -- Bruce Schneier

Bug#1106757: ppc64el Trixie: Need default 64KB page kernel or installer option

[Paul Gevers]

Hi Trupti,

On 23-07-2025 08:00, Trupti wrote:
as mentioned earlier, 64K 
is the recommended page size for ppc64el, and other distributions like 
Ubuntu already use it by default on Power.



Debian did so to *until* trixie. So, are you also discussing this with 
the kernel maintainers? If so, can you link the discussion to me please? 
A merge request to the release notes [1] suggest the kernel maintainers 
thought about the switch, so it seems like you're not well aligned with 
them or just have a disagreement about what should be the 
recommendation. Please feel free to (also) comment on that merge request.


Paul

[1] https://salsa.debian.org/ddp-team/release-notes/-/merge_requests/292


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Bug#1106757: ppc64el Trixie: Need default 64KB page kernel or installer option

[Pascal Hambourg]

On 23/07/2025 at 08:12, Cyril Brulebois wrote:

Pascal Hambourg  (2025-05-29):


AFAICS linux-image-powerpc64le-64k is not included in the DVD-1 image, so it
requires a network mirror. Same with linux-image-arm64-16k.


I suppose something like this might do the trick?

 kibi@tokyo:~/debian-cd/debian-cd.git (kibi/easy)$ git diff
 diff --git a/tools/generate_di+k_list b/tools/generate_di+k_list
 index 2bee6440..9801b932 100755
 --- a/tools/generate_di+k_list
 +++ b/tools/generate_di+k_list
 @@ -305,6 +305,7 @@ grub-ieee1275
  powerpc-utils
  powerpc-ibm-utils
  linux-image-powerpc64le
 +linux-image-powerpc64le-64k
  #endif
  
  #ifdef ARCH_alpha


I suppose so, if it pulls dependencies in.


This might push other packages out of the netinst though.


Trxie RC2 ppc64el netinst image size is only 545 MiB, so I suppose there 
is still some room on a CD (650 MiB) ? However it might push other 
packages out of the DVD-1 image.

Bug#1106757: ppc64el Trixie: Need default 64KB page kernel or installer option

[Cyril Brulebois]

Pascal Hambourg  (2025-05-29):
> (Removing kernel team)
> 
> On 29/05/2025 at 15:54, Cyril Brulebois wrote:
> > Trupti  (2025-05-29):
> > > 
> > > Add a clear installer option to select a 64KB page kernel.
> > 
> > I believe this should be offered in expert mode, have you tried that?
> 
> AFAICS linux-image-powerpc64le-64k is not included in the DVD-1 image, so it
> requires a network mirror. Same with linux-image-arm64-16k.

I suppose something like this might do the trick?

kibi@tokyo:~/debian-cd/debian-cd.git (kibi/easy)$ git diff
diff --git a/tools/generate_di+k_list b/tools/generate_di+k_list
index 2bee6440..9801b932 100755
--- a/tools/generate_di+k_list
+++ b/tools/generate_di+k_list
@@ -305,6 +305,7 @@ grub-ieee1275
 powerpc-utils
 powerpc-ibm-utils
 linux-image-powerpc64le
+linux-image-powerpc64le-64k
 #endif
 
 #ifdef ARCH_alpha

This might push other packages out of the netinst though.

Cc-ing debian-cd@, who is responsible for installation images.


Cheers,
-- 
Cyril Brulebois (k...@debian.org)
D-I release manager -- Release team member -- Freelance Consultant


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Bug#1106757: ppc64el Trixie: Need default 64KB page kernel or installer option

[Trupti]

On 2025-07-22 23:02, Paul Gevers wrote:

Hi,

On 22-07-2025 14:43, Trupti wrote:
I upgraded my system from Bookworm to Trixie using apt full-upgrade. 
The system is now running Trixie, but it's still using the old 
Bookworm kernel (6.1.0-37-powerpc64le).



Did you reboot? Can you check what you have in /boot?

Is there a way to make sure the system automatically installs and uses 
the latest 64K kernel during the upgrade?



Currently only by installing the non-default kernel. Because the
default upgrade path should install the 4k kernel.

Paul



Yes, I did reboot after the full upgrade. The system is now running the 
Trixie kernel, but it’s still using the default 4K page size. My goal 
was to upgrade to Trixie with the 64K kernel, but the upgrade path 
installs only the 4K kernel by default, and switching to 64K requires 
manually installing the linux-image-powerpc64le-64k package.


This isn’t just about avoiding manual steps — as mentioned earlier, 64K 
is the recommended page size for ppc64el, and other distributions like 
Ubuntu already use it by default on Power.


As Pascal pointed out earlier, offering this choice in the installer 
(e.g., via expert install) would require including the 64K kernel 
packages in the ISO image itself. That’s why I’m requesting that the 64K 
kernel be included in the installation images — so users can choose 
between kernel flavours at install time without needing post-install 
steps. It would be helpful if this could be considered for future Debian 
releases.



Thanks Trupti.

Bug#1106757: ppc64el Trixie: Need default 64KB page kernel or installer option

[Paul Gevers]

Hi,

On 22-07-2025 14:43, Trupti wrote:
I upgraded my system from Bookworm to Trixie using apt full-upgrade. The 
system is now running Trixie, but it's still using the old Bookworm 
kernel (6.1.0-37-powerpc64le).



Did you reboot? Can you check what you have in /boot?

Is there a way to make sure the system automatically installs and uses 
the latest 64K kernel during the upgrade?



Currently only by installing the non-default kernel. Because the default 
upgrade path should install the 4k kernel.


Paul



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Bug#1106757: ppc64el Trixie: Need default 64KB page kernel or installer option

[Trupti]

On 2025-07-20 14:18, Paul Gevers wrote:

Hi Trupti,

A small side note (just in case) because I got the impression that you
(and others at IBM) are not fully aware that Debian doesn't expect you
to use the Debian Installer to do system upgrades. We expect people to
just change the apt sources and run (a variant of) $(apt
full-upgrade).

Paul


Hi Paul,

Thanks for the suggestion.

I upgraded my system from Bookworm to Trixie using apt full-upgrade. The 
system is now running Trixie, but it's still using the old Bookworm 
kernel (6.1.0-37-powerpc64le).


Is there a way to make sure the system automatically installs and uses 
the latest 64K kernel during the upgrade?


Thanks Trupti

Bug#1106757: ppc64el Trixie: Need default 64KB page kernel or installer option

[Paul Gevers]

Hi Trupti,

A small side note (just in case) because I got the impression that you 
(and others at IBM) are not fully aware that Debian doesn't expect you 
to use the Debian Installer to do system upgrades. We expect people to 
just change the apt sources and run (a variant of) $(apt full-upgrade).


Paul


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Bug#1106757: ppc64el Trixie: Need default 64KB page kernel or installer option

[Trupti]

On 2025-06-13 02:31, Pascal Hambourg wrote:

On 29/05/2025 at 21:19, Pascal Hambourg wrote:

On 29/05/2025 at 15:54, Cyril Brulebois wrote:

Trupti  (2025-05-29):


Add a clear installer option to select a 64KB page kernel.


I believe this should be offered in expert mode, have you tried that?


AFAICS linux-image-powerpc64le-64k is not included in the DVD-1 image, 
so it requires a network mirror. Same with linux-image-arm64-16k.


Thinking twice, DVD-1 and netinst images set up a network mirror only
after installing the base system, so they only offer kernel flavours
included in installation images. Only netboot images set up a network
mirror before installing the base system and offer all kernel
flavours.



Hi Team,

I tested both the “Expert Install” workflow using the Trixie netinst ISO 
and the DVD installer for ppc64el. In both cases, only the 4K page-size 
kernel was available—there was no option to select the 64K kernel. As 
Pascal noted, the installer can only offer kernels that are already 
present on the ISO.


Could you please include the linux-image-ppc64le-64k package on the 
ppc64el installation ISOs for Trixie? This change would enable users to 
choose the 64K kernel directly during installation and ensure a smoother 
out-of-the-box experience on Power hardware.


Thanks Trupti

Re: Bug#1106757: ppc64el Trixie: Need default 64KB page kernel or installer option

[Trupti]

On 2025-07-02 23:25, Trupti wrote:

On 2025-06-26 01:08, Pascal Hambourg wrote:

[The mail I am replying to was sent to the bug but was not forwarded
to the list for some reason, although its size of 98ko is much smaller
than the previously observed limit of ~450-500ko. You can see it and
its attached screenshot at
]

On 25/06/2025 at 09:50, Trupti wrote:

On 2025-06-23 20:58, Trupti wrote:


To complete the end-to-end test scenario, I am now creating test 
files

on the Bookworm partitions.

I will proceed with the Trixie installation, manually preserving the
partitions, and will then verify the files are intact in the new
system. I will post the final results of this data integrity test 
here

soon.

(...)

You were absolutely right — I’ve completed the testing as suggested.

I tested ext4 (4K & 64K) and Btrfs partitions between Bookworm (64K 
kernel) and Trixie (4K kernel), and the following behavior was 
observed:


1]ext4 partitions with 4K block size worked fine — existing files 
were accessible without issues.


2]ext4 (64K) and Btrfs partitions couldn’t be mounted in Trixie 
(showed a "Mount Failed" error),

   and the installer failed unless those partitions were formatted.

ext4 with a 4K block size is compatible across both kernels. However, 
partitions created with a 64K block size (ext4 or Btrfs) are not 
supported by the 4K kernel. These need to be formatted during 
installation, which can lead to potential data loss.


To sum it up:
- With bookworm d-i and installed system 64k page size kernel,
mkfs.btrfs with default options and mke2fs -T largefile|largefile4
create filesystems with 64k block size.
- With trixie d-i 4k page size kernel, btrfs and ext* with 64k block
size filesystems are not supported and cannot be reused without being
reformatted with 4k block size (and losing data).

Shouldn't it at least be mentioned in ppc64el installation manual ?



Yes, I agree — this behavior should definitely be documented in the
ppc64el installation manual, especially to warn users about the
incompatibility and potential data loss when using ext4 or Btrfs
filesystems with 64k block size on a 4k page-size kernel.

Also, summarizing our discussion here regarding feasible solutions for
users who want to install a 64k page-size kernel from the beginning:

One possible option is to provide a dedicated official 64k ISO for 
ppc64el.


Another approach could be to include both 4k and 64k kernel variants
in the same ISO, allowing users to select the preferred option from
the boot menu — similar to what was done in older multi-arch
amd64+i386 images.

I kindly request the Debian Installer team to consider implementing
one of these installation options for Debian on PowerPC, so that users
who require a 64k setup can install it safely and directly.


Thanks Trupti


Looping Debian installer team.

Re: Bug#1106757: ppc64el Trixie: Need default 64KB page kernel or installer option

[Pascal Hambourg]

On 25/06/2025 at 21:38, Pascal Hambourg wrote:
[The mail I am replying to was sent to the bug but was not forwarded to 
the list for some reason, although its size of 98ko is much smaller than 
the previously observed limit of ~450-500ko. You can see it and its 
attached screenshot at ]


Now this is getting weird. My own reply did not make it to the list 
either. I suspect there was something in Trupti's mail and I quoted that 
some mail server did not like. Trying to send it directly to the list, 
with reply-to set to the bug...



On 25/06/2025 at 09:50, Trupti wrote:

On 2025-06-23 20:58, Trupti wrote:


To complete the end-to-end test scenario, I am now creating test files
on the Bookworm partitions.

I will proceed with the Trixie installation, manually preserving the
partitions, and will then verify the files are intact in the new
system. I will post the final results of this data integrity test here
soon.

(...)

You were absolutely right — I’ve completed the testing as suggested.

I tested ext4 (4K & 64K) and Btrfs partitions between Bookworm (64K 
kernel) and Trixie (4K kernel), and the following behavior was observed:


1]ext4 partitions with 4K block size worked fine — existing files were 
accessible without issues.


2]ext4 (64K) and Btrfs partitions couldn’t be mounted in Trixie 
(showed a "Mount Failed" error),

   and the installer failed unless those partitions were formatted.

ext4 with a 4K block size is compatible across both kernels. However, 
partitions created with a 64K block size (ext4 or Btrfs) are not 
supported by the 4K kernel. These need to be formatted during 
installation, which can lead to potential data loss.


To sum it up:
- With bookworm d-i and installed system 64k page size kernel, 
mkfs.btrfs with default options and mke2fs -T largefile|largefile4 
create filesystems with 64k block size.
- With trixie d-i 4k page size kernel, btrfs and ext* with 64k block 
size filesystems are not supported and cannot be reused without being 
reformatted with 4k block size (and losing data).


Shouldn't it at least be mentioned in ppc64el installation manual ?

Bug#1106757: ppc64el Trixie: Need default 64KB page kernel or installer option

[Trupti]

On 2025-06-20 16:10, Pascal Hambourg wrote:

On 20/06/2025 at 12:21, Trupti wrote:

On 2025-06-20 14:12, Pascal Hambourg wrote:


Can you check with "-T largefile" and without -T for completeness ?


Yes, I have performed the additional tests you requested for 
completeness.And the block size output for newly created partitions 
are as follow:


Thank you for taking the time to test.


root@debian:/home/usr# /sbin/tune2fs -l /dev/sda5 | grep "Block size"
Block size:   4096


I guess this one was created without -T ?


root@debian:/home/usr# /sbin/tune2fs -l /dev/sda4 | grep "Block size"
Block size:   65536


And this one with "-T largefile" ?

The results are the same: the Trixie installer was unable to use 
either partition without requiring a reformat.


The partition created with -T largefile was incompatible.


This is expected if the block size is 64k. However I guess -T is not
widely used.

The standard ext4 partition created without any -T option was also 
incompatible.


This is unexpected if the block size is 4k, and much more annoying.
What is the error message in kernel log ?


Hello Pascal,

To complete the end-to-end test scenario, I am now creating test files 
on the Bookworm partitions.


I will proceed with the Trixie installation, manually preserving the 
partitions, and will then verify the files are intact in the new system. 
I will post the final results of this data integrity test here soon.


Thank you.

Bug#1106757: ppc64el Trixie: Need default 64KB page kernel or installer option

[Pascal Hambourg]

On 20/06/2025 at 12:21, Trupti wrote:

On 2025-06-20 14:12, Pascal Hambourg wrote:


Can you check with "-T largefile" and without -T for completeness ?


Yes, I have performed the additional tests you requested for 
completeness.And the block size output for newly created partitions are 
as follow:


Thank you for taking the time to test.


root@debian:/home/usr# /sbin/tune2fs -l /dev/sda5 | grep "Block size"
Block size:   4096


I guess this one was created without -T ?


root@debian:/home/usr# /sbin/tune2fs -l /dev/sda4 | grep "Block size"
Block size:   65536


And this one with "-T largefile" ?

The results are the same: the Trixie installer was unable to use either 
partition without requiring a reformat.


The partition created with -T largefile was incompatible.


This is expected if the block size is 64k. However I guess -T is not 
widely used.


The standard ext4 partition created without any -T option was also 
incompatible.


This is unexpected if the block size is 4k, and much more annoying. What 
is the error message in kernel log ?

Bug#1106757: ppc64el Trixie: Need default 64KB page kernel or installer option

[Trupti]

On 2025-06-20 14:12, Pascal Hambourg wrote:

On 20/06/2025 à 09:18, Trupti wrote:


The Ext4 filesystem on /dev/sda5 was created using mkfs.ext4 -T 
largefile4 /dev/sda5.

Its block size is 64KB.


Can you check with "-T largefile" and without -T for completeness ?


Hi,

Yes, I have performed the additional tests you requested for 
completeness.And the block size output for newly created partitions are 
as follow:


root@debian:/home/usr# /sbin/tune2fs -l /dev/sda5 | grep "Block size"
Block size:   4096
root@debian:/home/usr# /sbin/tune2fs -l /dev/sda4 | grep "Block size"
Block size:   65536


The results are the same: the Trixie installer was unable to use either 
partition without requiring a reformat.


The partition created with -T largefile was incompatible.
The standard ext4 partition created without any -T option was also 
incompatible.


This creates a clear risk of data loss for users upgrading from 
Bookworm. To ensure a safe user experience, a dedicated 64k installer 
image is a necessity. Providing this for Trixie, and making it the 
default for future ppc64el releases, would prevent data loss and align 
Debian with platform standards.


Thanks Trupti.

Bug#1106757: ppc64el Trixie: Need default 64KB page kernel or installer option

[Pascal Hambourg]

On 20/06/2025 à 09:18, Trupti wrote:


The Ext4 filesystem on /dev/sda5 was created using mkfs.ext4 -T 
largefile4 /dev/sda5.

Its block size is 64KB.


Can you check with "-T largefile" and without -T for completeness ?

Bug#1106757: ppc64el Trixie: Need default 64KB page kernel or installer option

[Trupti]

On 2025-06-20 00:10, Pascal Hambourg wrote:

On 19/06/2025 at 20:16, Trupti wrote:


Both the 15GB Btrfs (/dev/sda4) and 30GB Ext4 (/dev/sda5) partitions, 
previously created with 64k page size (Bookworm), were recognized by 
the Trixie installer. However, neither could be assigned a mount point 
without requiring reformatting, implying data loss.


How was the ext4 filesystem created and what was its block size ?
You can see the block size with blkid or tune2fs -l.



The Ext4 filesystem on /dev/sda5 was created using mkfs.ext4 -T 
largefile4 /dev/sda5.

Its block size is 64KB.

To clarify how the Ext4 filesystem on /dev/sda5 was created and its 
block size, here is the command output used:



"root@debian:/home/usr# /sbin/mkfs.ext4 -T largefile4 /dev/sda5
mke2fs 1.47.0 (5-Feb-2023)
Creating filesystem with 491520 64k blocks and 8192 inodes
Filesystem UUID: 34c23dcc-c08d-4829-bcea-b1d99286a6e0
Superblock backups stored on blocks:
65528, 196584, 327640, 458696

Allocating group tables: done
Writing inode tables: done
Creating journal (8192 blocks): done
Writing superblocks and filesystem accounting information: done"


Thanks Trupti.

Bug#1106757: ppc64el Trixie: Need default 64KB page kernel or installer option

[Pascal Hambourg]

On 19/06/2025 at 20:16, Trupti wrote:


Both the 15GB Btrfs (/dev/sda4) and 30GB Ext4 (/dev/sda5) partitions, 
previously created with 64k page size (Bookworm), were recognized by the 
Trixie installer. However, neither could be assigned a mount point 
without requiring reformatting, implying data loss.


How was the ext4 filesystem created and what was its block size ?
You can see the block size with blkid or tune2fs -l.

Bug#1106757: ppc64el Trixie: Need default 64KB page kernel or installer option

[Pascal Hambourg]

On 17/06/2025 à 10:34, Trupti wrote:


Thank you,for the very helpful and detailed analysis of the potential 
btrfs and swap incompatibilities.


I do have access to ppc64el VMs and will perform the Bookworm-to-Trixie 
test scenario you described.


I will post my findings here shortly.


Ext* filesystems which have a block size larger than the kernel page 
size are also not supported. Big filesystems created with usage type 
(-T) "largefile" or "largefile4" might have a block size above 4k when 
the page size is 64k. But I do not have any hardware to test it.

Bug#1106757: ppc64el Trixie: Need default 64KB page kernel or installer option

[Trupti]

On 2025-06-13 02:31, Pascal Hambourg wrote:

On 29/05/2025 at 21:19, Pascal Hambourg wrote:

On 29/05/2025 at 15:54, Cyril Brulebois wrote:

Trupti  (2025-05-29):


Add a clear installer option to select a 64KB page kernel.


I believe this should be offered in expert mode, have you tried that?


AFAICS linux-image-powerpc64le-64k is not included in the DVD-1 image, 
so it requires a network mirror. Same with linux-image-arm64-16k.


Thinking twice, DVD-1 and netinst images set up a network mirror only
after installing the base system, so they only offer kernel flavours
included in installation images. Only netboot images set up a network
mirror before installing the base system and offer all kernel
flavours.

After reading #1079800 ("release-notes - Document that default ppc64el
kernel switched to 4k pages") [1], I thought about possible impact of
page size change on the installer, but do not have any ppc64 or arm64
hardware to test.

[1] 

The kernel supports a swap space only if it matches the page size.
The kernel supports a btrfs filesystem with a sector size equal to the
page size or 4k (aka subpage block size support, see [2][3]).

[2] 
[3]


Bookworm:
- linux-image-powerpc64le has 64k page size.
- mkswap creates swap with 64k page size.
- mkfs.btrfs creates filesystem with 64k sector size.

Trixie:
- linux-image-powerpc64le has 4k page size.
- mkswap creates swap with 4k page size.
- mkfs.btrfs creates filesystem with 4k sector size.

1) Impact on reuse of existing swap and btrfs filesystem:

The installer can detect (via libparted) and use an existing swap only
if it matches the installer kernel page size (4k). So it cannot use a
swap space created by a previous version with 64k page size without
reformatting it. No big deal though.

The installer can detect (via libparted) an existing btrfs filesystem
regardless of its sector size but can use it only if its sector size
is 4k. So it cannot use a btrfs filesystem created by a previous
version with 64k sector size without reformatting it (and losing all
its data).

2) Impact if linux-image-powerpc64le-64k (or linux-image-arm64-16k on
arm64) is selected:

systemd.swap seems to run swapon with --fixpgsz which reinitializes
the swap space if it does not match the kernel page size, so swap page
size mismatch should be fixed automatically during first boot.

A kernel with 64k page size is said to support btrfs filesystems with
either 4k or 64k sector size, so it should be able to mount btrfs
filesystems with 4k sector size created by Trixie installer.



Thank you,for the very helpful and detailed analysis of the potential 
btrfs and swap incompatibilities.


I do have access to ppc64el VMs and will perform the Bookworm-to-Trixie 
test scenario you described.


I will post my findings here shortly.

Thanks Trupti.

Bug#1106757: ppc64el Trixie: Need default 64KB page kernel or installer option

[Pascal Hambourg]

On 29/05/2025 at 21:19, Pascal Hambourg wrote:

On 29/05/2025 at 15:54, Cyril Brulebois wrote:

Trupti  (2025-05-29):


Add a clear installer option to select a 64KB page kernel.


I believe this should be offered in expert mode, have you tried that?


AFAICS linux-image-powerpc64le-64k is not included in the DVD-1 image, 
so it requires a network mirror. Same with linux-image-arm64-16k.


Thinking twice, DVD-1 and netinst images set up a network mirror only 
after installing the base system, so they only offer kernel flavours 
included in installation images. Only netboot images set up a network 
mirror before installing the base system and offer all kernel flavours.


After reading #1079800 ("release-notes - Document that default ppc64el 
kernel switched to 4k pages") [1], I thought about possible impact of 
page size change on the installer, but do not have any ppc64 or arm64 
hardware to test.


[1] 

The kernel supports a swap space only if it matches the page size.
The kernel supports a btrfs filesystem with a sector size equal to the 
page size or 4k (aka subpage block size support, see [2][3]).


[2] 
[3] 



Bookworm:
- linux-image-powerpc64le has 64k page size.
- mkswap creates swap with 64k page size.
- mkfs.btrfs creates filesystem with 64k sector size.

Trixie:
- linux-image-powerpc64le has 4k page size.
- mkswap creates swap with 4k page size.
- mkfs.btrfs creates filesystem with 4k sector size.

1) Impact on reuse of existing swap and btrfs filesystem:

The installer can detect (via libparted) and use an existing swap only 
if it matches the installer kernel page size (4k). So it cannot use a 
swap space created by a previous version with 64k page size without 
reformatting it. No big deal though.


The installer can detect (via libparted) an existing btrfs filesystem 
regardless of its sector size but can use it only if its sector size is 
4k. So it cannot use a btrfs filesystem created by a previous version 
with 64k sector size without reformatting it (and losing all its data).


2) Impact if linux-image-powerpc64le-64k (or linux-image-arm64-16k on 
arm64) is selected:


systemd.swap seems to run swapon with --fixpgsz which reinitializes the 
swap space if it does not match the kernel page size, so swap page size 
mismatch should be fixed automatically during first boot.


A kernel with 64k page size is said to support btrfs filesystems with 
either 4k or 64k sector size, so it should be able to mount btrfs 
filesystems with 4k sector size created by Trixie installer.

Bug#1106757: ppc64el Trixie: Need default 64KB page kernel or installer option

[Sachin Sant]

On Thu, 5 Jun 2025 20:41:58 +0300 Michael Tokarev  wrote:
> On 05.06.2025 16:15, Bastian Blank wrote:
> > On Thu, Jun 05, 2025 at 02:13:59PM +0300, Michael Tokarev wrote:
> >> But I know right to nothing about ppc64 and its page sizes.
> >
> > Okay, so we should remove kvm support from ppc64*, because it is not
> > supported anymore?
>
> I can't parse this sentence.
>
> There's an easy way to specify page size for a guest. I don't see any
> reason to disable kvm on ppc.
>

Right, there are 2 issues(64k page size kernel as default and KVM with 
4k kernel and 64k QEMU)

being discussed which aren't necessarily tied together.

While both 4K and 64K page size work on ppc64le, default recommended 
page size on ppc64le
is 64k. This is irrespective of KVM being or not. For the record Ubuntu 
on Power(and for that matter

other Linux lavors) also defaults to 64K page size and corresponding kernel.

For an out of box experience with Debian on Power, the request in this 
defect is for 64k page

size kernel to be made default during installation.

--
Thanks
- Sachin

Bug#1106757: ppc64el Trixie: Need default 64KB page kernel or installer option

[Michael Tokarev]

On 05.06.2025 16:15, Bastian Blank wrote:

On Thu, Jun 05, 2025 at 02:13:59PM +0300, Michael Tokarev wrote:

But I know right to nothing about ppc64 and its page sizes.


Okay, so we should remove kvm support from ppc64*, because it is not
supported anymore?


I can't parse this sentence.

There's an easy way to specify page size for a guest.  I don't see any
reason to disable kvm on ppc.

/mjt

Bug#1106757: ppc64el Trixie: Need default 64KB page kernel or installer option

[Lennart Sorensen]

On Thu, Jun 05, 2025 at 03:15:18PM +0200, Bastian Blank wrote:
> Okay, so we should remove kvm support from ppc64*, because it is not
> supported anymore?

It looked to me as if all you have to do is pass a command line argument
to qemu-kvm telling it to use 4k page size instead of the default 64k.
Doesn't mean it doesn't support kvm.

Changing the default sounds like it could break kvm migration between
hosts.  Perhaps it would be friendly if qemu would detect the page size
doesn't work and print a message telling the user what argument they
have to add to work with 4k page systems.

-- 
Len Sorensen

Bug#1106757: ppc64el Trixie: Need default 64KB page kernel or installer option

[Bastian Blank]

On Thu, Jun 05, 2025 at 02:13:59PM +0300, Michael Tokarev wrote:
> I definitely don't want to change upstream defaults here.

And noone asked for changed defaults, just overriding them when it
already saw it will not work.

Bastian

-- 
A princess should not be afraid -- not with a brave knight to protect her.
-- McCoy, "Shore Leave", stardate 3025.3

Bug#1106757: ppc64el Trixie: Need default 64KB page kernel or installer option

[Bastian Blank]

On Thu, Jun 05, 2025 at 02:13:59PM +0300, Michael Tokarev wrote:
> But I know right to nothing about ppc64 and its page sizes.

Okay, so we should remove kvm support from ppc64*, because it is not
supported anymore?

Bastian

-- 
Insults are effective only where emotion is present.
-- Spock, "Who Mourns for Adonais?"  stardate 3468.1

Bug#1106757: ppc64el Trixie: Need default 64KB page kernel or installer option

[Michael Tokarev]

On 04.06.2025 23:32, Bastian Blank wrote:

On Thu, May 29, 2025 at 04:04:43PM +0530, Trupti wrote:

Testing with the debian-testing-ppc64el-DVD-1.iso confirms that Debian
Trixie on ppc64el currently installs a 4KB page kernel by default. This
default (ref: #1074217) causes issues, especially for KVM virtualization
(e.g., "Can't support 64 kiB guest pages with 4 kiB host pages"), hindering
common ppc64el use cases. Debian Trixie should offer easier access to a 64KB
page size kernel.


This is a bug in qemu.


Make a 64KB page kernel the default for ppc64el Trixie.


We decided to make 4 KiB the default for all architectures.


https://lore.kernel.org/qemu-devel/aEFwmU8PRo_SxV4T@zatzit/

I definitely don't want to change upstream defaults here.

Maybe qemu upstream can be convinced to change their default
now (in the next version, not in trixie), I dunno.

But I know right to nothing about ppc64 and its page sizes.

Thanks,

/mjt

Bug#1106757: ppc64el Trixie: Need default 64KB page kernel or installer option

[Bastian Blank]

On Wed, Jun 04, 2025 at 10:32:13PM +0200, Bastian Blank wrote:
> On Thu, May 29, 2025 at 04:04:43PM +0530, Trupti wrote:
> > Testing with the debian-testing-ppc64el-DVD-1.iso confirms that Debian
> > Trixie on ppc64el currently installs a 4KB page kernel by default. This
> > default (ref: #1074217) causes issues, especially for KVM virtualization
> > (e.g., "Can't support 64 kiB guest pages with 4 kiB host pages"), hindering
> > common ppc64el use cases. Debian Trixie should offer easier access to a 64KB
> > page size kernel.
> 
> This is a bug in qemu.

Could you please contact the qemu maintainer via
1107...@bugs.debian.org?  I can only do theoretical work on a fix for
qemu, but you might have access to the hardware as well.

Bastian

-- 
Witch!  Witch!  They'll burn ya!
-- Hag, "Tomorrow is Yesterday", stardate unknown

Bug#1106757: ppc64el Trixie: Need default 64KB page kernel or installer option

[Bastian Blank]

On Thu, May 29, 2025 at 04:04:43PM +0530, Trupti wrote:
> Testing with the debian-testing-ppc64el-DVD-1.iso confirms that Debian
> Trixie on ppc64el currently installs a 4KB page kernel by default. This
> default (ref: #1074217) causes issues, especially for KVM virtualization
> (e.g., "Can't support 64 kiB guest pages with 4 kiB host pages"), hindering
> common ppc64el use cases. Debian Trixie should offer easier access to a 64KB
> page size kernel.

This is a bug in qemu.

> Make a 64KB page kernel the default for ppc64el Trixie.

We decided to make 4 KiB the default for all architectures.

Bastian

-- 
Vulcans never bluff.
-- Spock, "The Doomsday Machine", stardate 4202.1

Bug#1106757: ppc64el Trixie: Need default 64KB page kernel or installer option

[Pascal Hambourg]

(Removing kernel team)

On 29/05/2025 at 15:54, Cyril Brulebois wrote:

Trupti  (2025-05-29):


Add a clear installer option to select a 64KB page kernel.


I believe this should be offered in expert mode, have you tried that?


AFAICS linux-image-powerpc64le-64k is not included in the DVD-1 image, 
so it requires a network mirror. Same with linux-image-arm64-16k.

Bug#1106757: ppc64el Trixie: Need default 64KB page kernel or installer option

[Cyril Brulebois]

Hi,

Looping in the kernel team.

Trupti  (2025-05-29):
> Testing with the debian-testing-ppc64el-DVD-1.iso confirms that Debian
> Trixie on ppc64el currently installs a 4KB page kernel by default. This
> default (ref: #1074217) causes issues, especially for KVM virtualization
> (e.g., "Can't support 64 kiB guest pages with 4 kiB host pages"), hindering
> common ppc64el use cases. Debian Trixie should offer easier access to a 64KB
> page size kernel.
> 
> While 64KB kernel variants, such as those provided by the
> linux-image-powerpc64le-64k meta-package, are available in the Trixie
> archive, their manual installation post-setup is inconvenient.
> 
> Request:
> 
> Make a 64KB page kernel the default for ppc64el Trixie.

My reading of debian/config/ppc64el/defines.toml in kernel-team/linux.git
suggests they are responsible for setting up the default, not d-i.

> OR
> 
> Add a clear installer option to select a 64KB page kernel.

I believe this should be offered in expert mode, have you tried that?

> This would improve usability for ppc64el users needing 64KB pages for
> performance or virtualization.


Cheers,
-- 
Cyril Brulebois (k...@debian.org)
D-I release manager -- Release team member -- Freelance Consultant


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Bug#1106757: ppc64el Trixie: Need default 64KB page kernel or installer option

[Trupti]

Package: debian-installer
Severity: normal
Version: 20250515

Testing with the debian-testing-ppc64el-DVD-1.iso confirms that Debian 
Trixie on ppc64el currently installs a 4KB page kernel by default. This 
default (ref: #1074217) causes issues, especially for KVM virtualization 
(e.g., "Can't support 64 kiB guest pages with 4 kiB host pages"), 
hindering common ppc64el use cases. Debian Trixie should offer easier 
access to a 64KB page size kernel.


While 64KB kernel variants, such as those provided by the 
linux-image-powerpc64le-64k meta-package, are available in the Trixie 
archive, their manual installation post-setup is inconvenient.


Request:

Make a 64KB page kernel the default for ppc64el Trixie.
OR

Add a clear installer option to select a 64KB page kernel.

This would improve usability for ppc64el users needing 64KB pages for 
performance or virtualization.




Thanks and Regards,
Trupti