On 03.08.2021 15:30, Marek Marczykowski-Górecki wrote: > On Tue, Aug 03, 2021 at 03:16:14PM +0200, Jan Beulich wrote: >> 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. > > "upon admin override" - do I read the code right, that iommu=no-intremap > will actually achieve this effect?
In the case of this quirk - yes, as the call to the checking function is gated by a check of iommu_intremap. But by "admin override" I meant a per-guest attribute, not a host-wide one that isn't explicitly meant to cover all guests. > Will that allow to use IOMMU without > interrupt remapping on a hardware where it's broken? In that case, maybe > at least add this info to the log message? You mean to suggest the use of this option? I'd rather not, to be honest. I don't think options like this should be suggested to be used. I'd prefer if we had less of such options, i.e. if they went away after some initial integration phase. Jan
