Re: Linux: ioremap_page_range is no longer exported

[Jan Kiszka]

On 2017-02-03 10:11, Henning Schild wrote:
> On Thu, 2 Feb 2017 18:36:59 +0100
> Jan Kiszka  wrote:
> 
>> On 2017-02-02 18:17, Ralf Ramsauer wrote:
>>> Hi,
>>>
>>> upstream Linux commit 3277953 (mm: do not export ioremap_page_range
>>> symbol for external module) unexports the ioremap_page_range symbol,
>>> which we need for jailhouse_ioremap().
>>>
>>> The unexport was introduced in 4.10-rc6. To be able to load
>>> Jailhouse with Linux 4.10-rc6+, we either need to revert this
>>> commit, or use another API.
>>>
>>>   Ralf
>>>
>>> https://github.com/torvalds/linux/commit/3277953de2f31dd03c6375e9a9f680ac37fc9d27
>>>   
>>
>> Yeah, this increases pressure to rethink the handover procedure /wrt
>> address spaces. The simple workaround will be a kernel patch.
>> Long-term, it might be better to make Jailhouse relocatable (again)
>> and do this in the very early boot phase. Quite a bit of work,
>> though...
> 
> Not sure whether our case would be strong enough to get that change
> reverted upstream. At least looking at the discussion that led to the
> change and maybe talking to the author are probably not bad ideas.
> 
> The comment suggest there are plenty of alternatives, did not look
> further but it might just be a matter of using another ioremap_.

Currently, out requirement on the API is to define our own virtual
address for the mapping. All the mentioned ioremap_* variants do not
seem to cover this.

However, I'd first like to understand if we will need this fixed virtual
mapping on the Linux side also on the long run - before asking the
kernel to do some still out-of-tree component a favour. It's rather
unlikely they would do so anyway.

Jan

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Re: Linux: ioremap_page_range is no longer exported

[Henning Schild]

On Thu, 2 Feb 2017 18:36:59 +0100
Jan Kiszka  wrote:

> On 2017-02-02 18:17, Ralf Ramsauer wrote:
> > Hi,
> > 
> > upstream Linux commit 3277953 (mm: do not export ioremap_page_range
> > symbol for external module) unexports the ioremap_page_range symbol,
> > which we need for jailhouse_ioremap().
> > 
> > The unexport was introduced in 4.10-rc6. To be able to load
> > Jailhouse with Linux 4.10-rc6+, we either need to revert this
> > commit, or use another API.
> > 
> >   Ralf
> > 
> > https://github.com/torvalds/linux/commit/3277953de2f31dd03c6375e9a9f680ac37fc9d27
> >   
> 
> Yeah, this increases pressure to rethink the handover procedure /wrt
> address spaces. The simple workaround will be a kernel patch.
> Long-term, it might be better to make Jailhouse relocatable (again)
> and do this in the very early boot phase. Quite a bit of work,
> though...

Not sure whether our case would be strong enough to get that change
reverted upstream. At least looking at the discussion that led to the
change and maybe talking to the author are probably not bad ideas.

The comment suggest there are plenty of alternatives, did not look
further but it might just be a matter of using another ioremap_.

Henning

> Thanks,
> Jan
> 

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Re: Linux: ioremap_page_range is no longer exported

[Jan Kiszka]

On 2017-02-02 18:17, Ralf Ramsauer wrote:
> Hi,
> 
> upstream Linux commit 3277953 (mm: do not export ioremap_page_range
> symbol for external module) unexports the ioremap_page_range symbol,
> which we need for jailhouse_ioremap().
> 
> The unexport was introduced in 4.10-rc6. To be able to load Jailhouse
> with Linux 4.10-rc6+, we either need to revert this commit, or use
> another API.
> 
>   Ralf
> 
> https://github.com/torvalds/linux/commit/3277953de2f31dd03c6375e9a9f680ac37fc9d27
> 

Yeah, this increases pressure to rethink the handover procedure /wrt
address spaces. The simple workaround will be a kernel patch. Long-term,
it might be better to make Jailhouse relocatable (again) and do this in
the very early boot phase. Quite a bit of work, though...

Thanks,
Jan

-- 
Siemens AG, Corporate Technology, CT RDA ITP SES-DE
Corporate Competence Center Embedded Linux

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