diff options
| -rw-r--r-- | drivers/iommu/Kconfig | 26 | ||||
| -rw-r--r-- | drivers/iommu/dma-iommu.c | 2 |
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) { |