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Re: [PATCH] VT-d: Tylersburg errata apply to further steppings


  • To: Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>
  • From: Jan Beulich <jbeulich@xxxxxxxx>
  • Date: Tue, 3 Aug 2021 15:16:14 +0200
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  • Cc: "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Kevin Tian <kevin.tian@xxxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
  • Delivery-date: Tue, 03 Aug 2021 13:16:28 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>

On 03.08.2021 15:12, Marek Marczykowski-Górecki wrote:
> On Tue, Aug 03, 2021 at 03:06:50PM +0200, Jan Beulich wrote:
>> On 03.08.2021 15:01, Marek Marczykowski-Górecki wrote:
>>> Ok, then, just setting iommu_intremap=false should do the right thing,
>>
>> ... if "iommu=force" is in use (but not otherwise), ...
> 
> But that's the purpose of iommu=force, no?
> With "iommu=force": strictly require IOMMU
> Without "iommu=force": use IOMMU on best-effort basis
> 
> It makes sense to refuse the boot if intremap is broken in the first
> case. But also, it makes sense to allow using IOMMU without intremp in
> the second case.

I agree with both statements. What I disagree with is that the latter
happens by default (instead of only upon admin override), including
the case of intremap being unavailable in the first place.

Jan




 


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