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-rw-r--r--drivers/iommu/Kconfig26
-rw-r--r--drivers/iommu/dma-iommu.c2
2 files changed, 1 insertions, 27 deletions
diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
index 50bc6962c084..5c5cb5bee8b6 100644
--- a/drivers/iommu/Kconfig
+++ b/drivers/iommu/Kconfig
@@ -144,32 +144,6 @@ config IOMMU_DMA
select IRQ_MSI_IOMMU
select NEED_SG_DMA_LENGTH
-config IOMMU_DMA_PCI_SAC
- bool "Enable 64-bit legacy PCI optimisation by default"
- depends on IOMMU_DMA
- help
- Enable by default an IOMMU optimisation for 64-bit legacy PCI devices,
- wherein the DMA API layer will always first try to allocate a 32-bit
- DMA address suitable for a single address cycle, before falling back
- to allocating from the device's full usable address range. If your
- system has 64-bit legacy PCI devices in 32-bit slots where using dual
- address cycles reduces DMA throughput significantly, this may be
- beneficial to overall performance.
-
- If you have a modern PCI Express based system, this feature mostly just
- represents extra overhead in the allocation path for no practical
- benefit, and it should usually be preferable to say "n" here.
-
- However, beware that this feature has also historically papered over
- bugs where the IOMMU address width and/or device DMA mask is not set
- correctly. If device DMA problems and IOMMU faults start occurring
- after disabling this option, it is almost certainly indicative of a
- latent driver or firmware/BIOS bug, which would previously have only
- manifested with several gigabytes worth of concurrent DMA mappings.
-
- If this option is not set, the feature can still be re-enabled at
- boot time with the "iommu.forcedac=0" command-line argument.
-
# Shared Virtual Addressing
config IOMMU_SVA
bool
diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index 376c4e3ae0e6..17dd683b2fce 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -69,7 +69,7 @@ struct iommu_dma_cookie {
};
static DEFINE_STATIC_KEY_FALSE(iommu_deferred_attach_enabled);
-bool iommu_dma_forcedac __read_mostly = !IS_ENABLED(CONFIG_IOMMU_DMA_PCI_SAC);
+bool iommu_dma_forcedac __read_mostly;
static int __init iommu_dma_forcedac_setup(char *str)
{