Re: [PATCH v7 12/23] iommu/smmuv3: Get prepared for nested stage support

Auger Eric
2019-05-10T14:34:44Z

Hi Robin,

On 5/8/19 4:24 PM, Robin Murphy wrote:
> On 08/04/2019 13:19, Eric Auger wrote:
>> To allow nested stage support, we need to store both
>> stage 1 and stage 2 configurations (and remove the former
>> union).
>>
>> A nested setup is characterized by both s1_cfg and s2_cfg
>> set.
>>
>> We introduce a new ste.abort field that will be set upon
>> guest stage1 configuration passing. If s1_cfg is NULL and
>> ste.abort is set, traffic can't pass. If ste.abort is not set,
>> S1 is bypassed.
>>
>> arm_smmu_write_strtab_ent() is modified to write both stage
>> fields in the STE and deal with the abort field.
>>
>> In nested mode, only stage 2 is "finalized" as the host does
>> not own/configure the stage 1 context descriptor, guest does.
>>
>> Signed-off-by: Eric Auger <eric.auger@redhat.com>
>>
>> ---
>>
>> v4 -> v5:
>> - reset ste.abort on detach
>>
>> v3 -> v4:
>> - s1_cfg.nested_abort and nested_bypass removed.
>> - s/ste.nested/ste.abort
>> - arm_smmu_write_strtab_ent modifications with introduction
>>    of local abort, bypass and translate local variables
>> - comment updated
>>
>> v1 -> v2:
>> - invalidate the STE before moving from a live STE config to another
>> - add the nested_abort and nested_bypass fields
>> ---
>>   drivers/iommu/arm-smmu-v3.c | 35 ++++++++++++++++++++---------------
>>   1 file changed, 20 insertions(+), 15 deletions(-)
>>
>> diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c
>> index 21d027695181..e22e944ffc05 100644
>> --- a/drivers/iommu/arm-smmu-v3.c
>> +++ b/drivers/iommu/arm-smmu-v3.c
>> @@ -211,6 +211,7 @@
>>   #define STRTAB_STE_0_CFG_BYPASS        4
>>   #define STRTAB_STE_0_CFG_S1_TRANS    5
>>   #define STRTAB_STE_0_CFG_S2_TRANS    6
>> +#define STRTAB_STE_0_CFG_NESTED        7
>>     #define STRTAB_STE_0_S1FMT        GENMASK_ULL(5, 4)
>>   #define STRTAB_STE_0_S1FMT_LINEAR    0
>> @@ -514,6 +515,7 @@ struct arm_smmu_strtab_ent {
>>        * configured according to the domain type.
>>        */
>>       bool                assigned;
>> +    bool                abort;
>>       struct arm_smmu_s1_cfg        *s1_cfg;
>>       struct arm_smmu_s2_cfg        *s2_cfg;
>>   };
>> @@ -628,10 +630,8 @@ struct arm_smmu_domain {
>>       bool                non_strict;
>>         enum arm_smmu_domain_stage    stage;
>> -    union {
>> -        struct arm_smmu_s1_cfg    s1_cfg;
>> -        struct arm_smmu_s2_cfg    s2_cfg;
>> -    };
>> +    struct arm_smmu_s1_cfg    s1_cfg;
>> +    struct arm_smmu_s2_cfg    s2_cfg;
>>         struct iommu_domain        domain;
>>   @@ -1108,12 +1108,13 @@ static void arm_smmu_write_strtab_ent(struct
>> arm_smmu_device *smmu, u32 sid,
>>                         __le64 *dst, struct arm_smmu_strtab_ent *ste)
>>   {
>>       /*
>> -     * This is hideously complicated, but we only really care about
>> -     * three cases at the moment:
>> +     * We care about the following transitions:
>>        *
>>        * 1. Invalid (all zero) -> bypass/fault (init)
>> -     * 2. Bypass/fault -> translation/bypass (attach)
>> -     * 3. Translation/bypass -> bypass/fault (detach)
>> +     * 2. Bypass/fault -> single stage translation/bypass (attach)
>> +     * 3. single stage Translation/bypass -> bypass/fault (detach)
>> +     * 4. S2 -> S1 + S2 (attach_pasid_table)
>> +     * 5. S1 + S2 -> S2 (detach_pasid_table)
>>        *
>>        * Given that we can't update the STE atomically and the SMMU
>>        * doesn't read the thing in a defined order, that leaves us
>> @@ -1124,7 +1125,7 @@ static void arm_smmu_write_strtab_ent(struct
>> arm_smmu_device *smmu, u32 sid,
>>        * 3. Update Config, sync
>>        */
>>       u64 val = le64_to_cpu(dst[0]);
>> -    bool ste_live = false;
>> +    bool abort, bypass, translate, ste_live = false;
>>       struct arm_smmu_cmdq_ent prefetch_cmd = {
>>           .opcode        = CMDQ_OP_PREFETCH_CFG,
>>           .prefetch    = {
>> @@ -1138,11 +1139,11 @@ static void arm_smmu_write_strtab_ent(struct
>> arm_smmu_device *smmu, u32 sid,
>>               break;
>>           case STRTAB_STE_0_CFG_S1_TRANS:
>>           case STRTAB_STE_0_CFG_S2_TRANS:
>> +        case STRTAB_STE_0_CFG_NESTED:
>>               ste_live = true;
>>               break;
>>           case STRTAB_STE_0_CFG_ABORT:
>> -            if (disable_bypass)
>> -                break;
>> +            break;
>>           default:
>>               BUG(); /* STE corruption */
>>           }
>> @@ -1152,8 +1153,13 @@ static void arm_smmu_write_strtab_ent(struct
>> arm_smmu_device *smmu, u32 sid,
>>       val = STRTAB_STE_0_V;
>>         /* Bypass/fault */
>> -    if (!ste->assigned || !(ste->s1_cfg || ste->s2_cfg)) {
>> -        if (!ste->assigned && disable_bypass)
>> +
>> +    abort = (!ste->assigned && disable_bypass) || ste->abort;
>> +    translate = ste->s1_cfg || ste->s2_cfg;
>> +    bypass = !abort && !translate;
>> +
>> +    if (abort || bypass) {
>> +        if (abort)
>>               val |= FIELD_PREP(STRTAB_STE_0_CFG,
>> STRTAB_STE_0_CFG_ABORT);
>>           else
>>               val |= FIELD_PREP(STRTAB_STE_0_CFG,
>> STRTAB_STE_0_CFG_BYPASS);
>> @@ -1172,7 +1178,6 @@ static void arm_smmu_write_strtab_ent(struct
>> arm_smmu_device *smmu, u32 sid,
>>       }
>>         if (ste->s1_cfg) {
>> -        BUG_ON(ste_live);
>
> Hmm, I'm a little uneasy about just removing these checks altogether, as
> there are still cases where rewriting a live entry is bogus, that we'd
> really like to keep catching. Is the problem that it's hard to tell when
> you're 'rewriting' the S2 config of a nested entry with the same thing
> on attaching/detaching its S1 context?
No, I restored the original checks in !nested mode and added a new check
to make sure we never update a live S1 in nested mode. Only S2 can be live.

Thanks

Eric
>
> Robin.
>
>>           dst[1] = cpu_to_le64(
>>                FIELD_PREP(STRTAB_STE_1_S1CIR,
>> STRTAB_STE_1_S1C_CACHE_WBRA) |
>>                FIELD_PREP(STRTAB_STE_1_S1COR,
>> STRTAB_STE_1_S1C_CACHE_WBRA) |
>> @@ -1191,7 +1196,6 @@ static void arm_smmu_write_strtab_ent(struct
>> arm_smmu_device *smmu, u32 sid,
>>       }
>>         if (ste->s2_cfg) {
>> -        BUG_ON(ste_live);
>>           dst[2] = cpu_to_le64(
>>                FIELD_PREP(STRTAB_STE_2_S2VMID, ste->s2_cfg->vmid) |
>>                FIELD_PREP(STRTAB_STE_2_VTCR, ste->s2_cfg->vtcr) |
>> @@ -1773,6 +1777,7 @@ static void arm_smmu_detach_dev(struct device *dev)
>>       }
>>         master->ste.assigned = false;
>> +    master->ste.abort = false;
>>       arm_smmu_install_ste_for_dev(fwspec);
>>   }
>>