[PATCH] iommu/arm-smmu-v2: Workaround for ThunderX errata#27704

Chalamarla, Tirumalesh
2016-02-05T20:32:00Z

On 2/5/16, 12:02 PM, "Mark Rutland" <mark.rutland@arm.com> wrote:

>On Fri, Feb 05, 2016 at 10:47:07AM -0800, tchalamarla at caviumnetworks.com wrote:
>> From: Tirumalesh Chalamarla <tchalamarla@caviumnetworks.com>
>>
>> An issue exists whereby the Linux kernel requires that ASIDs are a
>> unique namespace per SMMU.
>
>The SMMU architecture requires this, and Linux relies on hardware
>following the architecture.
>
>Please describe the problem correctly. i.e. that the hardware
>erroneously shares TLBs between SMMU instances.
>
>> That ASID-local choice conflicts with the
>> CN88xx SMMU, where only shared ASID namespaces are supported;
>> specifically within a given node SMMU0 and SMMU1 share, as does SMMU2
>> and SMMU3. CN88xx SMMU also requires global VMIDs.
>>
>> This patch tries to address these issuee by supplying asid and vmid
>> transformations from devicetree.
>>
>> Signed-off-by: Akula Geethasowjanya <Geethasowjanya.Akula@caviumnetworks.com>
>> Signed-off-by: Tirumalesh Chalamarla <tchalamarla@caviumnetworks.com>
>> ---
>> .../devicetree/bindings/iommu/arm,smmu.txt | 16 ++++++
>> drivers/iommu/arm-smmu.c | 59 ++++++++++++++++++----
>> 2 files changed, 65 insertions(+), 10 deletions(-)
>>
>> diff --git a/Documentation/devicetree/bindings/iommu/arm,smmu.txt b/Documentation/devicetree/bindings/iommu/arm,smmu.txt
>> index 7180745..eef06d0 100644
>> --- a/Documentation/devicetree/bindings/iommu/arm,smmu.txt
>> +++ b/Documentation/devicetree/bindings/iommu/arm,smmu.txt
>> @@ -55,6 +55,22 @@ conditions.
>> aliases of secure registers have to be used during
>> SMMU configuration.
>>
>> +- thunderx,smmu-asid-transform : Enable proper handling for buggy
>> + implementations that require special transformations
>> + for smmu asid. if this property exists asid-transform
>> + property must be present.
>> +
>> +- thunderx,smmu-vmid-transform : Enable proper handling for buggy
>> + implementations that require special transformations
>> + for smmu vmid. if this property exists vmid-transform
>> + property must be present.
>> +
>> +- asid-transform : Transform mask that needs to be applied to asid.
>> + This property has to be specified as '/bits/ 8' value.
>> +
>> +- vmid-transform : Transform mask that needs to be applied to vmid.
>> + This property has to be specified as '/bits/ 8' value.
>
>Don't bother with /bits/ 8. It saves no space in the DTB and only adds
>to confusion. Use a full cell, and of_property_read_u32, and validate
>that the value is in range.
>
>Having two properties for each seems redundant. The presence of a mask
>should be sufficient to make it clear that the use of the mask is
>required.

Sure.
>
>These properties aren't sufficiently described. How is the mask
>"applied", and what is it applied to? What constraints does it impose
>on the OS's selection of ASIDs/VMIDs?
>
>From the looks of the patch, it's ANDed into the value Linux has
>selected, so it sounds like an OS must avoid using any bits set in any
>mask on any SMMU instance. That sounds very difficult to ensure in
>general, and very fragile.

For now it is only specific to ThunderX errata, its not a general requirement.
So ThunderX DTS will make sure it defined proper values.

If all agree to make it a general requirement, I am happy to re write it with ASID and VMID coming from
DTS.
>
>Mark.
>
>> +
>> Example:
>>
>> smmu {
>> diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
>> index 59ee4b8..8047834 100644
>> --- a/drivers/iommu/arm-smmu.c
>> +++ b/drivers/iommu/arm-smmu.c
>> @@ -300,8 +300,12 @@ struct arm_smmu_device {
>> u32 features;
>>
>> #define ARM_SMMU_OPT_SECURE_CFG_ACCESS (1 << 0)
>> +#define ARM_SMMU_OPT_TRANSFORM_ASID (1 << 1)
>> +#define ARM_SMMU_OPT_TRANSFORM_VMID (1 << 2)
>> u32 options;
>> enum arm_smmu_arch_version version;
>> + u8 asid_transform;
>> + u8 vmid_transform;
>>
>> u32 num_context_banks;
>> u32 num_s2_context_banks;
>> @@ -330,8 +334,25 @@ struct arm_smmu_cfg {
>> };
>> #define INVALID_IRPTNDX 0xff
>>
>> -#define ARM_SMMU_CB_ASID(cfg) ((cfg)->cbndx)
>> -#define ARM_SMMU_CB_VMID(cfg) ((cfg)->cbndx + 1)
>> +/*
>> + * ThunderX has a unique requirement because of ERRATA#27704
>> + * An issue exists whereby the Linux kernel requires that ASIDs are a
>> + * unique namespace per SMMU. That ASID-local choice conflicts with the
>> + * CN88xx SMMU, where only shared ASID namespaces are supported;
>> + * specifically within a given node SMMU0 and SMMU1 share, as does SMMU2
>> + * and SMMU3.
>> + * CN88xx SMMU also requires global VMIDs.
>> + */
>> +
>> +#define ARM_SMMU_CB_ASID(smmu, cfg) \
>> + (((smmu)->options & ARM_SMMU_OPT_TRANSFORM_ASID) \
>> + ? ((cfg)->cbndx | (smmu)->asid_transform) \
>> + : ((cfg)->cbndx))
>> +
>> +#define ARM_SMMU_CB_VMID(smmu, cfg) \
>> + (((smmu)->options & ARM_SMMU_OPT_TRANSFORM_VMID) \
>> + ? (((cfg)->cbndx + 1) | (smmu)->vmid_transform) \
>> + : ((cfg)->cbndx + 1))
>>
>> enum arm_smmu_domain_stage {
>> ARM_SMMU_DOMAIN_S1 = 0,
>> @@ -361,6 +382,8 @@ struct arm_smmu_option_prop {
>>
>> static struct arm_smmu_option_prop arm_smmu_options[] = {
>> { ARM_SMMU_OPT_SECURE_CFG_ACCESS, "calxeda,smmu-secure-config-access" },
>> + { ARM_SMMU_OPT_TRANSFORM_ASID, "thunderx,smmu-asid-transform" },
>> + { ARM_SMMU_OPT_TRANSFORM_VMID, "thunderx,smmu-vmid-transform" },
>> { 0, NULL},
>> };
>>
>> @@ -570,11 +593,11 @@ static void arm_smmu_tlb_inv_context(void *cookie)
>>
>> if (stage1) {
>> base = ARM_SMMU_CB_BASE(smmu) + ARM_SMMU_CB(smmu, cfg->cbndx);
>> - writel_relaxed(ARM_SMMU_CB_ASID(cfg),
>> + writel_relaxed(ARM_SMMU_CB_ASID(smmu, cfg),
>> base + ARM_SMMU_CB_S1_TLBIASID);
>> } else {
>> base = ARM_SMMU_GR0(smmu);
>> - writel_relaxed(ARM_SMMU_CB_VMID(cfg),
>> + writel_relaxed(ARM_SMMU_CB_VMID(smmu, cfg),
>> base + ARM_SMMU_GR0_TLBIVMID);
>> }
>>
>> @@ -596,7 +619,7 @@ static void arm_smmu_tlb_inv_range_nosync(unsigned long iova, size_t size,
>>
>> if (!IS_ENABLED(CONFIG_64BIT) || smmu->version == ARM_SMMU_V1) {
>> iova &= ~12UL;
>> - iova |= ARM_SMMU_CB_ASID(cfg);
>> + iova |= ARM_SMMU_CB_ASID(smmu, cfg);
>> do {
>> writel_relaxed(iova, reg);
>> iova += granule;
>> @@ -604,7 +627,7 @@ static void arm_smmu_tlb_inv_range_nosync(unsigned long iova, size_t size,
>> #ifdef CONFIG_64BIT
>> } else {
>> iova >>= 12;
>> - iova |= (u64)ARM_SMMU_CB_ASID(cfg) << 48;
>> + iova |= (u64)ARM_SMMU_CB_ASID(smmu, cfg) << 48;
>> do {
>> writeq_relaxed(iova, reg);
>> iova += granule >> 12;
>> @@ -624,7 +647,7 @@ static void arm_smmu_tlb_inv_range_nosync(unsigned long iova, size_t size,
>> #endif
>> } else {
>> reg = ARM_SMMU_GR0(smmu) + ARM_SMMU_GR0_TLBIVMID;
>> - writel_relaxed(ARM_SMMU_CB_VMID(cfg), reg);
>> + writel_relaxed(ARM_SMMU_CB_VMID(smmu, cfg), reg);
>> }
>> }
>>
>> @@ -752,7 +775,7 @@ static void arm_smmu_init_context_bank(struct arm_smmu_domain *smmu_domain,
>> reg |= (CBAR_S1_BPSHCFG_NSH << CBAR_S1_BPSHCFG_SHIFT) |
>> (CBAR_S1_MEMATTR_WB << CBAR_S1_MEMATTR_SHIFT);
>> } else {
>> - reg |= ARM_SMMU_CB_VMID(cfg) << CBAR_VMID_SHIFT;
>> + reg |= ARM_SMMU_CB_VMID(smmu, cfg) << CBAR_VMID_SHIFT;
>> }
>> writel_relaxed(reg, gr1_base + ARM_SMMU_GR1_CBAR(cfg->cbndx));
>>
>> @@ -760,11 +783,11 @@ static void arm_smmu_init_context_bank(struct arm_smmu_domain *smmu_domain,
>> if (stage1) {
>> reg64 = pgtbl_cfg->arm_lpae_s1_cfg.ttbr[0];
>>
>> - reg64 |= ((u64)ARM_SMMU_CB_ASID(cfg)) << TTBRn_ASID_SHIFT;
>> + reg64 |= ((u64)ARM_SMMU_CB_ASID(smmu, cfg)) << TTBRn_ASID_SHIFT;
>> smmu_writeq(reg64, cb_base + ARM_SMMU_CB_TTBR0);
>>
>> reg64 = pgtbl_cfg->arm_lpae_s1_cfg.ttbr[1];
>> - reg64 |= ((u64)ARM_SMMU_CB_ASID(cfg)) << TTBRn_ASID_SHIFT;
>> + reg64 |= ((u64)ARM_SMMU_CB_ASID(smmu, cfg)) << TTBRn_ASID_SHIFT;
>> smmu_writeq(reg64, cb_base + ARM_SMMU_CB_TTBR1);
>> } else {
>> reg64 = pgtbl_cfg->arm_lpae_s2_cfg.vttbr;
>> @@ -1793,6 +1816,22 @@ static int arm_smmu_device_dt_probe(struct platform_device *pdev)
>>
>> parse_driver_options(smmu);
>>
>> + if (smmu->options & ARM_SMMU_OPT_TRANSFORM_ASID) {
>> + if (of_property_read_u8(dev->of_node, "#asid-transform",
>> + &smmu->asid_transform)) {
>> + dev_err(dev, "missing #asid-transform property\n");
>> + return -ENODEV;
>> + }
>> + }
>> +
>> + if (smmu->options & ARM_SMMU_OPT_TRANSFORM_VMID) {
>> + if (of_property_read_u8(dev->of_node, "#vmid-transform",
>> + &smmu->vmid_transform)) {
>> + dev_err(dev, "missing #vmid-transform property\n");
>> + return -ENODEV;
>> + }
>> + }
>> +
>` if (smmu->version > ARM_SMMU_V1 &&
>> smmu->num_context_banks != smmu->num_context_irqs) {
>> dev_err(dev,
>> --
>> 2.1.0
>>
>>
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