On Tue, 2015-11-24 at 13:53 -0800, Shaohua Li wrote: > Currently if a device has rmrr or the device is a pci device, > passthrough is disabled even with iommu=pt. The worry is moving such > devices between domains don't work. But some users don't do the domain > reassignment at all, disabling passthough punish everybody. And iommu=pt > is a boot option, user knows the risk. So intead of failing the > passthough, just print a warning and continue the passthough.
We tend to suggest that iommu=pt gives you performance for the *decent* devices, while dubious devices still get translated. So your crappy 32- bit devices still get translated. And anything unfortunate enough to have an RMRR can *still* get translated. I'm reluctant to change that. If it hurts you, kick your system vendor until they stop doing stupid things with RMRRs. I think we also need to revisit the whole 'iommu=pt' thing anyway and define the semantics we expect across archiectures — given that SPARC and POWER are doing passthrough for 'decent' devices by *default*. So let's not tweak it right now. -- David Woodhouse Open Source Technology Centre [email protected] Intel Corporation
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