On 2018/8/9 19:08, Robin Murphy wrote:
> On 06/08/18 13:27, Zhen Lei wrote:
>> 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 <[email protected]>
>> ---
>> 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.
OK，I will change it in the next version.
>
> Robin.
>
>> + 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
>>
>>
>
> .
>
--
Thanks!
BestRegards
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