Merge: redhat/configs: replace IOMMU_DEFAULT_DMA_STRICT with IOMMU_DEFAULT_DMA_LAZY

MR: https://gitlab.com/redhat/centos-stream/src/kernel/centos-stream-9/-/merge_requests/6014

JIRA: https://issues.redhat.com/browse/RHEL-69993
Upstream Status: RHEL-only

    At least since 5.14.0-460.el9 RHEL kernels include s390 DMA API conversion patch
    series which went upstream with v6.7.
    (https://lore.kernel.org/all/20230928-dma_iommu-v13-0-9e5fc4dacc36@linux.ibm.com/).

    With this series the IOMMU_DEFAULT_DMA_(STRICT|LAZY) Kconfig options become relevant
    for s390 PCI devices, they were ineffective before.

    As part of the series drivers/iommu/Kconfig was adjusted to default
    to IOMMU_DEFAULT_DMA_LAZY=y for s390. Despite this default RHEL kernels have set
    IOMMU_DEFAULT_DMA_STRICT=y instead. In testing this leads to a severe performance
    degradation of up to 60% for network workloads and possibly also RCU stall warnings.

Signed-off-by: Mete Durlu <mdurlu@redhat.com>

Approved-by: Jerry Snitselaar <jsnitsel@redhat.com>
Approved-by: Donald Dutile <ddutile@redhat.com>
Approved-by: CKI KWF Bot <cki-ci-bot+kwf-gitlab-com@redhat.com>

Merged-by: Rado Vrbovsky <rvrbovsk@redhat.com>

Author: emmil

redhat/configs/rhel/generic/s390x/CONFIG_IOMMU_DEFAULT_DMA_LAZY

@@ -0,0 +1,13 @@
+# Symbol: IOMMU_DEFAULT_DMA_LAZY [=n]
+# Type  : bool
+# Defined at drivers/iommu/Kconfig:108
+#   Prompt: Translated - Lazy
+#   Depends on: <choice>
+#   Location:
+#     -> Device Drivers
+#       -> IOMMU Hardware Support (IOMMU_SUPPORT [=y])
+#         -> IOMMU default domain type (<choice> [=y])
+# 
+# 
+# 
+CONFIG_IOMMU_DEFAULT_DMA_LAZY=y

redhat/configs/rhel/generic/s390x/CONFIG_IOMMU_DEFAULT_DMA_STRICT

@@ -0,0 +1 @@
+# CONFIG_IOMMU_DEFAULT_DMA_STRICT is not set