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Re: Xorg fails on ATI after update (mmio aperture)



On Fri, Mar 24, 2017 at 02:43:56PM +0100, Riccardo Mottola wrote:
> Hi,
> 
> John Paul Adrian Glaubitz wrote:
> > Quoting:
> > 
> > > >If this option is disabled, you allow userspace (root) access to all
> > > >io-memory regardless of whether a driver is actively using that range.
> > > >Accidental access to this is obviously disastrous, but specific access
> > > >can be used by people debugging kernel drivers.
> > Allowing this configuration in the default kernel sounds like a very bad
> > idea and I don't think Debian's kernel maintainers will agree to change
> > this setting.
> > 
> > I'm afraid you will have to keep building your kernel from source.
> If it is a security options which has a serious impact on user laptop or
> desktop machines. We are saying that most probably default instal without a
> kernel rebuild is without X for many users of cards with legacy drivers.
> On a laptop I have less security concerns than on a server and run dangerous
> applications like X11 and a browser like firefox!
> 
> Can it be kept on on PPC 32bit only? Especially since we know it has a
> larger legacy hardware base than others. Probably on 64bit nobody has such
> video cards,  I imagine I am not the only one running Xorg legacy.
> 
> Compiling a kernel is not really difficult but quite  time consuming.
> 
> I still think a bug should be opened thus - where should I do it, now that
> we aren't a release arch anymore?
> 
> Riccardo

Can you boot the default Debian kernel (the one with
CONFIG_IO_STRICT_DEVMEM=y) with the following boot parameter and see if
it works for you?

iomem=relaxed

If that works, you are open to some "security" issues, but no need to
build a new kernel. Maybe adding that option by default on a system with
such a card would be a nice-to-have on the Debian Installer, but that's
it.

Cascardo.


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