Re: [Xen-devel] [PATCH 1/1] keep iommu disabled until iommu_setup is called

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 19.10.12 at 02:35, Ronny Hegewald <ronny.hegewald@xxxxxxxxx> wrote:
>>  The concept is plausible, but I'm not convinced that there aren't
>> any users of iommu_enabled that actually depend on it having
>> its final value after command line parsing, yet before
>> iommu_setup() gets called. 
> 
> But that is currently only true for systems with a iommu. For the ones 
> without 
> one have iommu_enabled=1 first, until iommu_setup() is called and 
> iommu_enabled is set to 0 because of the not detectable iommu.

That's a valid argument.

> So, with or without my patch, a similiar problem seems to be present, just 
> for different systems.
> 
>> Did you fully audit all users?
> 
> No, because there is just no way i can make a meaningfull judgement how the 
> iommu code interdepends with all the other parts that check iommu_enabled. 

I did a brief check, and it seems to be okay. I guess we'll have to
deal with eventual fallout then.

>> As to the patch itself, ...
> 
> I will send a 2. version which addresses your comments as soon its clear if 
> the approach in the patch is the right one to fix the crash.

Please do.

Jan


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