On 2024/9/5 15:22, Joerg Roedel wrote:
From: Joerg Roedel<jroedel@xxxxxxx>
Add two new kernel command line parameters to limit the page-sizes
used for v1 page-tables:
nohugepages - Limits page-sizes to 4KiB
v2_pgsizes_only - Limits page-sizes to 4Kib/2Mib/1GiB; The
same as the sizes used with v2 page-tables
This is needed for multiple scenarios. When assigning devices to
SEV-SNP guests the IOMMU page-sizes need to match the sizes in the RMP
table, otherwise the device will not be able to access all shared
memory.
Also, some ATS devices do not work properly with arbitrary IO
page-sizes as supported by AMD-Vi, so limiting the sizes used by the
driver is a suitable workaround.
All-in-all, these parameters are only workarounds until the IOMMU core
and related APIs gather the ability to negotiate the page-sizes in a
better way.
Signed-off-by: Joerg Roedel<jroedel@xxxxxxx>
---
Documentation/admin-guide/kernel-parameters.txt | 17 +++++++++++------
drivers/iommu/amd/amd_iommu.h | 1 +
drivers/iommu/amd/amd_iommu_types.h | 4 ++++
drivers/iommu/amd/init.c | 8 ++++++++
drivers/iommu/amd/io_pgtable.c | 2 +-
5 files changed, 25 insertions(+), 7 deletions(-)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 09126bb8cc9f..6d6630aec46c 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -333,12 +333,17 @@
allowed anymore to lift isolation
requirements as needed. This option
does not override iommu=pt
- force_enable - Force enable the IOMMU on platforms known
- to be buggy with IOMMU enabled. Use this
- option with care.
- pgtbl_v1 - Use v1 page table for DMA-API (Default).
- pgtbl_v2 - Use v2 page table for DMA-API.
- irtcachedis - Disable Interrupt Remapping Table (IRT) caching.
+ force_enable - Force enable the IOMMU on platforms known
+ to be buggy with IOMMU enabled. Use this
+ option with care.
+ pgtbl_v1 - Use v1 page table for DMA-API (Default).
+ pgtbl_v2 - Use v2 page table for DMA-API.
+ irtcachedis - Disable Interrupt Remapping Table (IRT) caching.
+ nohugepages - Limit page-sizes used for v1 page-tables
+ to 4 KiB.
Intel iommu driver has a similar option 'intel_iommu=sp_off'
sp_off [Default Off]
By default, super page will be supported if Intel IOMMU
has the capability. With this option, super page will
not be supported.
Is it possible to consolidate these two into a single
"iommu.nohugepages=1"?
+ v2_pgsizes_only - Limit page-sizes used for v1 page-tables
+ to 4KiB/2Mib/1GiB.
+
amd_iommu_dump= [HW,X86-64]
Enable AMD IOMMU driver option to dump the ACPI table
Thanks,
baolu
