On 08.09.20 14:40, Jan-Marc Stranz wrote:
What do I really need in the kernel configuration and kernel command
line for IOMMU support?
If I set
CONFIG_IOMMU_SUPPORT=y
in the kernel configuration then the system starts.
If I set
CONFIG_IOMMU_SUPPORT=y
and
CONFIG_INTEL_IOMMU=y
in the kernel configuration the system does not start!
This is not a Jailhouse issue. If you found a kernel configuration that
does not boot your board, report to the kernel provider (I assume
upstream), possibly also board/BIOS vendor. Include the boot log.
And also make sure to cross-check with a standard distribution kernel as
well (all major distros have INTEL_IOMMU on). You are on x86, booting a
standard distro should be no problem.
Setting
CONFIG_INTEL_IOMMU
also sets
CONFIG_IOMMU_IOVA=y
CONFIG_IOMMU_API=y
CONFIG_DMAR_TABLE=y
CONFIG_INTEL_IOMMU_FLOPPY_WA=y
automatically.
For the kernel command line there are two options:
iommu=off|noforce|force|...
and
intel_iommu=on|off|...
What do I really need for the hypervisor "jailhouse"?
For Jailhouse, both turning off the IOMMU support in the root kernel
completely and leaving only interrupt remapping on but dmar
(intel_iommu=) off will work. The latter gives better performance, though.
So, if you are using a standard kernel (or the config provided by
jailhouse-images), you just need to flip to intel_iommu=off for starting
Jailhouse. Leave it on for creating the config only, as I wrote before.
Jan
--
Siemens AG, Corporate Technology, CT RDA IOT SES-DE
Corporate Competence Center Embedded Linux
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