[PATCH v4 5/5] iommu/arm-smmu-v3: add bootup option "arm_iommu"
From: robin.murphy@arm.com (Robin Murphy)
Date: 2018-08-09 11:08:43
Also in:
linux-iommu, lkml
On 06/08/18 13:27, Zhen Lei wrote:
quoted hunk ↗ jump to hunk
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 | 9 +++++++++ drivers/iommu/arm-smmu-v3.c | 17 ++++++++++++++++- 2 files changed, 25 insertions(+), 1 deletion(-)diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 533ff5c..426e989 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt@@ -1720,6 +1720,15 @@ nobypass [PPC/POWERNV] Disable IOMMU bypass, using IOMMU for PCI devices. + arm_iommu= [ARM64] + non-strict [Default Off]
Again, I'd much rather have "iommu.non_strict= { "0" | "1" }" in line
with the passthrough option.
Robin.
quoted hunk ↗ jump to hunk
+ 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 904bc1e..9a30892 100644 --- a/drivers/iommu/arm-smmu-v3.c +++ b/drivers/iommu/arm-smmu-v3.c@@ -631,6 +631,21 @@ struct arm_smmu_option_prop { { 0, NULL}, }; +static u32 smmu_non_strict __read_mostly; + +static int __init arm_smmu_setup(char *str) +{ + if (!strncmp(str, "non-strict", 10)) { + smmu_non_strict = 1; + 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("arm_iommu", arm_smmu_setup); + static inline void __iomem *arm_smmu_page1_fixup(unsigned long offset, struct arm_smmu_device *smmu) {@@ -1622,7 +1637,7 @@ 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 = 1; pgtbl_cfg.quirks |= IO_PGTABLE_QUIRK_NON_STRICT; } --1.8.3