From 712d8f205835c1d170e85d7811da3d9f36d8fab7 Mon Sep 17 00:00:00 2001 From: Zhen Lei Date: Mon, 12 Jul 2021 19:12:17 +0800 Subject: [PATCH] iommu: Enhance IOMMU default DMA mode build options First, add build options IOMMU_DEFAULT_{LAZY|STRICT}, so that we have the opportunity to set {lazy|strict} mode as default at build time. Then put the two config options in an choice, as they are mutually exclusive. [jpg: Make choice between strict and lazy only (and not passthrough)] Signed-off-by: Zhen Lei Signed-off-by: John Garry Reviewed-by: Robin Murphy Reviewed-by: Lu Baolu Link: https://lore.kernel.org/r/1626088340-5838-4-git-send-email-john.garry@huawei.com Signed-off-by: Joerg Roedel --- Documentation/admin-guide/kernel-parameters.txt | 3 +- drivers/iommu/Kconfig | 40 +++++++++++++++++++++++++ drivers/iommu/iommu.c | 2 +- 3 files changed, 43 insertions(+), 2 deletions(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index a04d274..90b525c 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -2042,9 +2042,10 @@ throughput at the cost of reduced device isolation. Will fall back to strict mode if not supported by the relevant IOMMU driver. - 1 - Strict mode (default). + 1 - Strict mode. DMA unmap operations invalidate IOMMU hardware TLBs synchronously. + unset - Use value of CONFIG_IOMMU_DEFAULT_{LAZY,STRICT}. Note: on x86, the default behaviour depends on the equivalent driver-specific parameters, but a strict mode explicitly specified by either method takes diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig index 07b7c25..9cd5d7a 100644 --- a/drivers/iommu/Kconfig +++ b/drivers/iommu/Kconfig @@ -90,6 +90,46 @@ config IOMMU_DEFAULT_PASSTHROUGH If unsure, say N here. +choice + prompt "IOMMU default DMA IOTLB invalidation mode" + depends on IOMMU_DMA + + default IOMMU_DEFAULT_STRICT + help + This option allows an IOMMU DMA IOTLB invalidation mode to be + chosen at build time, to override the default mode of each ARCH, + removing the need to pass in kernel parameters through command line. + It is still possible to provide common boot params to override this + config. + + If unsure, keep the default. + +config IOMMU_DEFAULT_STRICT + bool "strict" + help + For every IOMMU DMA unmap operation, the flush operation of IOTLB and + the free operation of IOVA are guaranteed to be done in the unmap + function. + +config IOMMU_DEFAULT_LAZY + bool "lazy" + help + Support lazy mode, where for every IOMMU DMA unmap operation, the + flush operation of IOTLB and the free operation of IOVA are deferred. + They are only guaranteed to be done before the related IOVA will be + reused. + + The isolation provided in this mode is not as secure as STRICT mode, + such that a vulnerable time window may be created between the DMA + unmap and the mappings cached in the IOMMU IOTLB or device TLB + finally being invalidated, where the device could still access the + memory which has already been unmapped by the device driver. + However this mode may provide better performance in high throughput + scenarios, and is still considerably more secure than passthrough + mode or no IOMMU. + +endchoice + config OF_IOMMU def_bool y depends on OF && IOMMU_API diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c index 69d7d48..bd9ccce 100644 --- a/drivers/iommu/iommu.c +++ b/drivers/iommu/iommu.c @@ -30,7 +30,7 @@ static struct kset *iommu_group_kset; static DEFINE_IDA(iommu_group_ida); static unsigned int iommu_def_domain_type __read_mostly; -static bool iommu_dma_strict __read_mostly = true; +static bool iommu_dma_strict __read_mostly = IS_ENABLED(CONFIG_IOMMU_DEFAULT_STRICT); static u32 iommu_cmd_line __read_mostly; struct iommu_group { -- 2.7.4