Messages in this thread | | | Subject | Re: [PATCH v3 6/6] iommu/arm-smmu-v3: add bootup option "iommu_strict_mode" | From | "Leizhen (ThunderTown)" <> | Date | Thu, 26 Jul 2018 15:41:06 +0800 |
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On 2018/7/25 6:46, Robin Murphy wrote: > On 2018-07-12 7:18 AM, Zhen Lei wrote: >> Because the non-strict mode introduces a vulnerability window, so add a >> bootup option to make the manager can choose which mode to be used. The >> default mode is IOMMU_STRICT. >> >> Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com> >> --- >> Documentation/admin-guide/kernel-parameters.txt | 12 ++++++++++ >> drivers/iommu/arm-smmu-v3.c | 32 ++++++++++++++++++++++--- >> 2 files changed, 41 insertions(+), 3 deletions(-) >> >> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt >> index efc7aa7..0cc80bc 100644 >> --- a/Documentation/admin-guide/kernel-parameters.txt >> +++ b/Documentation/admin-guide/kernel-parameters.txt >> @@ -1720,6 +1720,18 @@ >> nobypass [PPC/POWERNV] >> Disable IOMMU bypass, using IOMMU for PCI devices. >> + iommu_strict_mode= [arm-smmu-v3] > > If anything this should belong to iommu-dma, as that's where the actual decision of whether to use a flush queue or not happens. Also it would be nice to stick to the iommu.* option namespace in the hope of maintaining some consistency.
How about arm_iommu? like "s390_iommu" and "intel_iommu". After all it only affect smmu now.
> >> + 0 - strict mode >> + Make sure all related TLBs to be invalidated before the >> + memory released. >> + 1 - non-strict mode >> + Put off TLBs invalidation and release memory first. This mode >> + introduces a vlunerability window, 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 is always use strict mode. >> + others - 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 4a198a0..9b72fc4 100644 >> --- a/drivers/iommu/arm-smmu-v3.c >> +++ b/drivers/iommu/arm-smmu-v3.c >> @@ -631,6 +631,24 @@ struct arm_smmu_option_prop { >> { 0, NULL}, >> }; >> +static u32 iommu_strict_mode __read_mostly = IOMMU_STRICT; >> + >> +static int __init setup_iommu_strict_mode(char *str) >> +{ >> + u32 strict_mode = IOMMU_STRICT; >> + >> + get_option(&str, &strict_mode); >> + if (strict_mode == IOMMU_NON_STRICT) { >> + iommu_strict_mode = strict_mode; >> + pr_warn("WARNING: iommu non-strict mode is chose.\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_strict_mode", setup_iommu_strict_mode); >> + >> static inline void __iomem *arm_smmu_page1_fixup(unsigned long offset, >> struct arm_smmu_device *smmu) >> { >> @@ -1441,7 +1459,7 @@ static bool arm_smmu_capable(enum iommu_cap cap) >> case IOMMU_CAP_NOEXEC: >> return true; >> case IOMMU_CAP_NON_STRICT: >> - return true; >> + return (iommu_strict_mode == IOMMU_NON_STRICT) ? true : false; > > Ugh. The "completely redundant ternany" idiom hurts my soul :(
OK, I will modify it.
> > Robin. > >> default: >> return false; >> } >> @@ -1750,6 +1768,14 @@ static int arm_smmu_attach_dev(struct iommu_domain *domain, struct device *dev) >> return ret; >> } >> +static u32 arm_smmu_strict_mode(struct iommu_domain *domain) >> +{ >> + if (iommu_strict_mode == IOMMU_NON_STRICT) >> + return IOMMU_DOMAIN_STRICT_MODE(domain); >> + >> + return IOMMU_STRICT; >> +} >> + >> static int arm_smmu_map(struct iommu_domain *domain, unsigned long iova, >> phys_addr_t paddr, size_t size, int prot) >> { >> @@ -1769,7 +1795,7 @@ static int arm_smmu_map(struct iommu_domain *domain, unsigned long iova, >> if (!ops) >> return 0; >> - return ops->unmap(ops, iova | IOMMU_DOMAIN_STRICT_MODE(domain), size); >> + return ops->unmap(ops, iova | arm_smmu_strict_mode(domain), size); >> } >> static void arm_smmu_flush_iotlb_all(struct iommu_domain *domain) >> @@ -1784,7 +1810,7 @@ static void arm_smmu_iotlb_sync(struct iommu_domain *domain) >> { >> struct arm_smmu_device *smmu = to_smmu_domain(domain)->smmu; >> - if (smmu && (IOMMU_DOMAIN_STRICT_MODE(domain) == IOMMU_STRICT)) >> + if (smmu && (arm_smmu_strict_mode(domain) == IOMMU_STRICT)) >> __arm_smmu_tlb_sync(smmu); >> } >> > > . >
-- Thanks! BestRegards
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