[PATCH v5 5/5] iommu/arm-smmu-v3: add bootup option "iommu.non_strict"
From: Zhen Lei <hidden>
Date: 2018-08-15 01:32:48
Also in:
linux-iommu, lkml
Subsystem:
documentation, iommu subsystem, the rest · Maintainers:
Jonathan Corbet, Joerg Roedel, Will Deacon, Linus Torvalds
Add a bootup option to make the system manager can choose which mode to be used. The default mode is strict. Signed-off-by: Zhen Lei <redacted> --- Documentation/admin-guide/kernel-parameters.txt | 13 +++++++++++++ drivers/iommu/arm-smmu-v3.c | 22 +++++++++++++++++++++- 2 files changed, 34 insertions(+), 1 deletion(-)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 5cde1ff..cb9d043e 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt@@ -1720,6 +1720,19 @@ nobypass [PPC/POWERNV] Disable IOMMU bypass, using IOMMU for PCI devices. + iommu.non_strict= [ARM64] + Format: { "0" | "1" } + 0 - strict mode, default. + Release IOVAs after the related TLBs are invalid + completely. + 1 - non-strict mode. + Put off TLBs invalidation and release memory first. + It's good for scatter-gather performance but lacks + full isolation, an untrusted device can access the + reused memory because the TLBs may still valid. + Please take full consideration before choosing this + mode. Note that, VFIO will always use strict mode. + iommu.passthrough= [ARM64] Configure DMA to bypass the IOMMU by default. Format: { "0" | "1" }
diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c
index 61eb7ec..0eda90e 100644
--- a/drivers/iommu/arm-smmu-v3.c
+++ b/drivers/iommu/arm-smmu-v3.c@@ -631,6 +631,26 @@ struct arm_smmu_option_prop { { 0, NULL}, }; +static bool smmu_non_strict __read_mostly; + +static int __init arm_smmu_setup(char *str) +{ + int ret; + + ret = kstrtobool(str, &smmu_non_strict); + if (ret) + return ret; + + if (smmu_non_strict) { + pr_warn("WARNING: iommu non-strict mode is chosen.\n" + "It's good for scatter-gather performance but lacks full isolation\n"); + add_taint(TAINT_WARN, LOCKDEP_STILL_OK); + } + + return 0; +} +early_param("iommu.non_strict", arm_smmu_setup); + static inline void __iomem *arm_smmu_page1_fixup(unsigned long offset, struct arm_smmu_device *smmu) {
@@ -1622,7 +1642,7 @@ static int arm_smmu_domain_finalise(struct iommu_domain *domain) if (smmu->features & ARM_SMMU_FEAT_COHERENCY) pgtbl_cfg.quirks = IO_PGTABLE_QUIRK_NO_DMA; - if (domain->type == IOMMU_DOMAIN_DMA) { + if ((domain->type == IOMMU_DOMAIN_DMA) && smmu_non_strict) { domain->non_strict = true; pgtbl_cfg.quirks |= IO_PGTABLE_QUIRK_NON_STRICT; } --
1.8.3