UBUNTU: [Config] enable Intel DMA remapping by default

BugLink: https://bugs.launchpad.net/bugs/1951440

We have tried in the past to enable CONFIG_INTEL_IOMMU_DEFAULT_ON and
CONFIG_INTEL_IOMMU_SCALABLE_MODE_DEFAULT_ON (starting with Jammy), but
there were multiple issues (especially with old hardware), so we ended
up disabling these options afterwards, see LP: #1971699.

Considering that IOMMU is enabled by default in upstream kernels,
probably most of these issues are solved now (or old hardware has been
decommissioned).

Moreover, having this enabled by default can prevent potential issues
with modern hardware and drivers (see for example LP #1958004).

Acked-by: Philip Cox <[email protected]>
Acked-by: Andrei Gherzan <[email protected]>
Signed-off-by: Andrea Righi <[email protected]>

Author: Andrea Righi

debian.master/config/annotations

@@ -321,8 +321,11 @@ CONFIG_INTEL_ATOMISP                            note<'LP: #2017444'>
 CONFIG_INTEL_ATOMISP2_PM                        policy<{'amd64': 'm'}>
 CONFIG_INTEL_ATOMISP2_PM                        note<'LP: #2017444'>
 
-CONFIG_INTEL_IOMMU_DEFAULT_ON                   policy<{'amd64': 'n'}>
-CONFIG_INTEL_IOMMU_DEFAULT_ON                   note<'LP: #1971699'>
+CONFIG_INTEL_IOMMU_DEFAULT_ON                   policy<{'amd64': 'y'}>
+CONFIG_INTEL_IOMMU_DEFAULT_ON                   note<'LP: #1951440'>
+
+CONFIG_INTEL_IOMMU_SCALABLE_MODE_DEFAULT_ON     policy<{'amd64': 'y'}>
+CONFIG_INTEL_IOMMU_SCALABLE_MODE_DEFAULT_ON     note<'LP: #1951440'>
 
 CONFIG_IOMMU_DEBUGFS                            policy<{'amd64': 'n', 'arm64': 'n', 'armhf': 'n', 'ppc64el': 'n', 'riscv64': 'n', 's390x': 'n'}>
 CONFIG_IOMMU_DEBUGFS                            note<'LP: #1861057'>