Re: [PATCH v13 05/15] iommu/smmuv3: Get prepared for nested stage support

[Auger Eric]

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@xxxxxxxxxx>
>>
>> ---
>> 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
>