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SubjectRe: [PATCH v13 05/15] iommu/smmuv3: Get prepared for nested stage support
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Hi Keqian,

On 2/2/21 8:14 AM, Keqian Zhu wrote:
> Hi Eric,
>
> On 2020/11/18 19:21, Eric Auger wrote:
>> When nested stage translation is setup, both s1_cfg and
>> s2_cfg are set.
>>
>> We introduce a new smmu domain abort field that will be set
>> upon guest stage1 configuration passing.
>>
>> 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>
>>
>> ---
>> v10 -> v11:
>> - Fix an issue reported by Shameer when switching from with vSMMU
>> to without vSMMU. Despite the spec does not seem to mention it
>> seems to be needed to reset the 2 high 64b when switching from
>> S1+S2 cfg to S1 only. Especially dst[3] needs to be reset (S2TTB).
>> On some implementations, if the S2TTB is not reset, this causes
>> a C_BAD_STE error
>> ---
>> drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 64 +++++++++++++++++----
>> drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h | 2 +
>> 2 files changed, 56 insertions(+), 10 deletions(-)
>>
>> diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
>> index 18ac5af1b284..412ea1bafa50 100644
>> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
>> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
>> @@ -1181,8 +1181,10 @@ static void arm_smmu_write_strtab_ent(struct arm_smmu_master *master, u32 sid,
>> * three cases at the moment:
>> *
>> * 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 or nested stage Translation/bypass -> bypass/fault (detach)
>> + * 4. S2 -> S1 + S2 (attach_pasid_table)
>> + * 5. S1 + S2 -> S2 (detach_pasid_table)
>
> The following line "BUG_ON(ste_live && !nested);" forbids this transform.

Yes as pointed out by Kunkun, there is always an abort in-between. I
will restore the original comment.

> And I have a look at the 6th patch, the transform seems S1 + S2 -> abort.
> So after detach, the status is not the same as that before attach. Does it
> match our expectation?

Indeed at detach time I think I should reset the abort() flag as this
latter is not imposed anymore by the guest.

Thanks!

Eric


>
>> *
>> * Given that we can't update the STE atomically and the SMMU
>> * doesn't read the thing in a defined order, that leaves us
>> @@ -1193,7 +1195,8 @@ static void arm_smmu_write_strtab_ent(struct arm_smmu_master *master, u32 sid,
>> * 3. Update Config, sync
>> */
>> u64 val = le64_to_cpu(dst[0]);
>> - bool ste_live = false;
>> + bool s1_live = false, s2_live = false, ste_live;
>> + bool abort, nested = false, translate = false;
>> struct arm_smmu_device *smmu = NULL;
>> struct arm_smmu_s1_cfg *s1_cfg;
>> struct arm_smmu_s2_cfg *s2_cfg;
>> @@ -1233,6 +1236,8 @@ static void arm_smmu_write_strtab_ent(struct arm_smmu_master *master, u32 sid,
>> default:
>> break;
>> }
>> + nested = s1_cfg->set && s2_cfg->set;
>> + translate = s1_cfg->set || s2_cfg->set;
>> }
>>
>> if (val & STRTAB_STE_0_V) {
>> @@ -1240,23 +1245,36 @@ static void arm_smmu_write_strtab_ent(struct arm_smmu_master *master, u32 sid,
>> case STRTAB_STE_0_CFG_BYPASS:
>> break;
>> case STRTAB_STE_0_CFG_S1_TRANS:
>> + s1_live = true;
>> + break;
>> case STRTAB_STE_0_CFG_S2_TRANS:
>> - ste_live = true;
>> + s2_live = true;
>> + break;
>> + case STRTAB_STE_0_CFG_NESTED:
>> + s1_live = true;
>> + s2_live = true;
>> break;
>> case STRTAB_STE_0_CFG_ABORT:
>> - BUG_ON(!disable_bypass);
>> break;
>> default:
>> BUG(); /* STE corruption */
>> }
>> }
>>
>> + ste_live = s1_live || s2_live;
>> +
>> /* Nuke the existing STE_0 value, as we're going to rewrite it */
>> val = STRTAB_STE_0_V;
>>
>> /* Bypass/fault */
>> - if (!smmu_domain || !(s1_cfg->set || s2_cfg->set)) {
>> - if (!smmu_domain && disable_bypass)
>> +
>> + if (!smmu_domain)
>> + abort = disable_bypass;
>> + else
>> + abort = smmu_domain->abort;
>> +
>> + if (abort || !translate) {
>> + 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);
>> @@ -1274,8 +1292,16 @@ static void arm_smmu_write_strtab_ent(struct arm_smmu_master *master, u32 sid,
>> return;
>> }
>>
>> + BUG_ON(ste_live && !nested);
>> +
>> + if (ste_live) {
>> + /* First invalidate the live STE */
>> + dst[0] = cpu_to_le64(STRTAB_STE_0_CFG_ABORT);
>> + arm_smmu_sync_ste_for_sid(smmu, sid);
>> + }
>> +
> [...]
>
> Thanks,
> Keqian
>

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