[PATCH 00/11 v3] Cleanup IOMMU passthrough setting (and disable IOMMU Passthrough when SME is active

Joerg Roedel
2019-08-19T13:22:45Z

Hi,

This patch-set started out small to overwrite the default passthrough
setting (through CONFIG_IOMMU_DEFAULT_PASSTHROUGH=y) when SME is active.

But on the way to that Tom reminded me that the current ways to
configure passthrough/no-passthrough modes for IOMMU on x86 is a mess.
So I added a few more patches to clean that up a bit, getting rid of the
iommu_pass_through variable on the way.This information is now kept only
in iommu code, with helpers to change that setting from architecture
code.

And of course this patch-set still disables IOMMU Passthrough mode when
SME is active even when CONFIG_IOMMU_DEFAULT_PASSTHROUGH=y is set.

The reason for that change is that SME with passthrough mode turned out
to be fragile with devices requiring SWIOTLB, mainly because SWIOTLB has
a maximum allocation size of 256kb and a limit overall size of the
bounce buffer.

Therefore having IOMMU in translation mode by default is better when SME
is active on a system.

Please review.

Thanks,

Joerg

Changes since v2:

- Added 'bool cmd_line' parameter to iommu_set_default_*()
functions, so that we correctly recognize iommu=pt/nopt
command line parameters

Changes since v1:

- Cleaned up the kernel command line parameters to
configure passthrough/translated mode, getting rid
of the global iommu_pass_through variable

Joerg Roedel (11):
iommu: Remember when default domain type was set on kernel command line
iommu: Add helpers to set/get default domain type
iommu: Use Functions to set default domain type in iommu_set_def_domain_type()
iommu/amd: Request passthrough mode from IOMMU core
iommu/vt-d: Request passthrough mode from IOMMU core
x86/dma: Get rid of iommu_pass_through
ia64: Get rid of iommu_pass_through
iommu: Print default domain type on boot
iommu: Set default domain type at runtime
iommu: Disable passthrough mode when SME is active
Documentation: Update Documentation for iommu.passthrough

Documentation/admin-guide/kernel-parameters.txt | 2 +-
arch/ia64/include/asm/iommu.h | 2 -
arch/ia64/kernel/pci-dma.c | 2 -
arch/x86/include/asm/iommu.h | 1 -
arch/x86/kernel/pci-dma.c | 20 +-----
drivers/iommu/amd_iommu.c | 6 +-
drivers/iommu/intel-iommu.c | 2 +-
drivers/iommu/iommu.c | 93 +++++++++++++++++++++++--
include/linux/iommu.h | 16 +++++
9 files changed, 110 insertions(+), 34 deletions(-)

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2.16.4