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Re: [Xen-devel] [BUG] After upgrade to Xen 4.12.0 iommu=no-igfx
- To: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Roman Shaposhnik <roman@xxxxxxxxxx>
- From: Jan Beulich <JBeulich@xxxxxxxx>
- Date: Wed, 31 Jul 2019 09:30:50 +0000
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- Cc: Juergen Gross <JGross@xxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>, "boris.ostrovsky@xxxxxxxxxx" <boris.ostrovsky@xxxxxxxxxx>, Paul Durrant <Paul.Durrant@xxxxxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>
- Delivery-date: Wed, 31 Jul 2019 09:46:37 +0000
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- Thread-topic: [Xen-devel] [BUG] After upgrade to Xen 4.12.0 iommu=no-igfx
On 31.07.2019 10:58, Andrew Cooper wrote:
> On 31/07/2019 09:34, Jan Beulich wrote:
>> On 30.07.2019 19:56, Roman Shaposhnik wrote:
>>> On Fri, Jul 26, 2019 at 1:06 AM Jan Beulich <JBeulich@xxxxxxxx> wrote:
>>>> On 23.07.2019 20:25, Roman Shaposhnik wrote:
>>>>> Interestingly enough, adding iommu_inclusive_mapping=1 AND iommu=debug
>>>>> booted the system just fine.
>>>> Btw (I've noticed this only now) - are you saying without "iommu=debug"
>>>> the box does _not_ boot fine, despite the other option?
>>> Yes. But it made sense to me since iommu=debug (as per your
>>> explanation) overwhelms the CPU and I guess adding
>>> iommu_inclusive_mapping=1 avoids the code path that does it?
>> I'm afraid I don't follow: My question was whether
>> "iommu_inclusive_mapping=1" alone would not allow the box to boot.
>> Without "iommu=debug" there's no excessive logging afaict, no
>> matter what other IOMMU options you use.
>
> Without inclusive mappings, the system boots but the screen is junk and
> there are DMA faults all over the place. With inclusive mappings, it
> all "works" fine.
>
> With debug enabled, the DMA faults are spat out to the console for a
> short while, until an APIC error occurs and the system wedges completely.
Right - the verbosity _with_ "iommu=debug" may be a problem. Hence me
wondering whether the system indeed wouldn't boot _without_ that option.
Jan
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