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Diffstat (limited to 'drivers/firmware/efi/Kconfig')
| -rw-r--r-- | drivers/firmware/efi/Kconfig | 22 |
1 files changed, 22 insertions, 0 deletions
diff --git a/drivers/firmware/efi/Kconfig b/drivers/firmware/efi/Kconfig index bcc378c19ebe..ecc83e2f032c 100644 --- a/drivers/firmware/efi/Kconfig +++ b/drivers/firmware/efi/Kconfig @@ -215,6 +215,28 @@ config EFI_RCI2_TABLE Say Y here for Dell EMC PowerEdge systems. +config EFI_DISABLE_PCI_DMA + bool "Clear Busmaster bit on PCI bridges during ExitBootServices()" + help + Disable the busmaster bit in the control register on all PCI bridges + while calling ExitBootServices() and passing control to the runtime + kernel. System firmware may configure the IOMMU to prevent malicious + PCI devices from being able to attack the OS via DMA. However, since + firmware can't guarantee that the OS is IOMMU-aware, it will tear + down IOMMU configuration when ExitBootServices() is called. This + leaves a window between where a hostile device could still cause + damage before Linux configures the IOMMU again. + + If you say Y here, the EFI stub will clear the busmaster bit on all + PCI bridges before ExitBootServices() is called. This will prevent + any malicious PCI devices from being able to perform DMA until the + kernel reenables busmastering after configuring the IOMMU. + + This option will cause failures with some poorly behaved hardware + and should not be enabled without testing. The kernel commandline + options "efi=disable_early_pci_dma" or "efi=no_disable_early_pci_dma" + may be used to override this option. + endmenu config UEFI_CPER |