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Subject: Re: [PATCH v13 05/15] iommu/smmuv3: Get prepared for nested stage
 support
To:     Kunkun Jiang <jiangkunkun@huawei.com>, eric.auger.pro@gmail.com,
        iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org,
        kvm@vger.kernel.org, kvmarm@lists.cs.columbia.edu, will@kernel.org,
        joro@8bytes.org, maz@kernel.org, robin.murphy@arm.com,
        alex.williamson@redhat.com
Cc:     jean-philippe@linaro.org, zhangfei.gao@linaro.org,
        zhangfei.gao@gmail.com, vivek.gautam@arm.com,
        shameerali.kolothum.thodi@huawei.com,
        jacob.jun.pan@linux.intel.com, yi.l.liu@intel.com, tn@semihalf.com,
        nicoleotsuka@gmail.com, yuzenghui@huawei.com,
        wanghaibin.wang@huawei.com, Keqian Zhu <zhukeqian1@huawei.com>
References: <20201118112151.25412-1-eric.auger@redhat.com>
 <20201118112151.25412-6-eric.auger@redhat.com>
 <a40b90bd-6756-c8cc-b455-c093d16d35f5@huawei.com>
From:   Auger Eric <eric.auger@redhat.com>
Message-ID: <096c2c79-84b2-75d4-094f-bdd8b0a2d125@redhat.com>
Date:   Thu, 3 Dec 2020 14:01:41 +0100
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Hi Kunkun,

On 12/3/20 1:32 PM, Kunkun Jiang 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:
> Now, it should be *five cases*.
>>  	 *
>>  	 * 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)
> 
> I was testing this series on one of our hardware board with SMMUv3. And
> I found while trying to /"//attach_pasid_table//"/,
> 
> the sequence of STE (host) config(bit[3:1]) is /"S2->abort->S1 + S2"/.
> Because the maintenance is  /"Write everything apart///
> 
> /from dword 0, sync, write dword 0, sync"/ when we update the STE
> (guest). Dose the sequence meet your expectation?

yes it does. I will fix the comments accordingly.

Is there anything to correct in the code or was it functional?

Thanks

Eric
> 
>> +	 * 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
>> @@ -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);
>> +	}
>> +
>>  	if (s1_cfg->set) {
>> -		BUG_ON(ste_live);
>> +		BUG_ON(s1_live);
>>  		dst[1] = cpu_to_le64(
>>  			 FIELD_PREP(STRTAB_STE_1_S1DSS, STRTAB_STE_1_S1DSS_SSID0) |
>>  			 FIELD_PREP(STRTAB_STE_1_S1CIR, STRTAB_STE_1_S1C_CACHE_WBRA) |
>> @@ -1294,7 +1320,14 @@ static void arm_smmu_write_strtab_ent(struct arm_smmu_master *master, u32 sid,
>>  	}
>>  
>>  	if (s2_cfg->set) {
>> -		BUG_ON(ste_live);
>> +		u64 vttbr = s2_cfg->vttbr & STRTAB_STE_3_S2TTB_MASK;
>> +
>> +		if (s2_live) {
>> +			u64 s2ttb = le64_to_cpu(dst[3] & STRTAB_STE_3_S2TTB_MASK);
>> +
>> +			BUG_ON(s2ttb != vttbr);
>> +		}
>> +
>>  		dst[2] = cpu_to_le64(
>>  			 FIELD_PREP(STRTAB_STE_2_S2VMID, s2_cfg->vmid) |
>>  			 FIELD_PREP(STRTAB_STE_2_VTCR, s2_cfg->vtcr) |
>> @@ -1304,9 +1337,12 @@ static void arm_smmu_write_strtab_ent(struct arm_smmu_master *master, u32 sid,
>>  			 STRTAB_STE_2_S2PTW | STRTAB_STE_2_S2AA64 |
>>  			 STRTAB_STE_2_S2R);
>>  
>> -		dst[3] = cpu_to_le64(s2_cfg->vttbr & STRTAB_STE_3_S2TTB_MASK);
>> +		dst[3] = cpu_to_le64(vttbr);
>>  
>>  		val |= FIELD_PREP(STRTAB_STE_0_CFG, STRTAB_STE_0_CFG_S2_TRANS);
>> +	} else {
>> +		dst[2] = 0;
>> +		dst[3] = 0;
>>  	}
>>  
>>  	if (master->ats_enabled)
>> @@ -1982,6 +2018,14 @@ static int arm_smmu_domain_finalise(struct iommu_domain *domain,
>>  		return 0;
>>  	}
>>  
>> +	if (smmu_domain->stage == ARM_SMMU_DOMAIN_NESTED &&
>> +	    (!(smmu->features & ARM_SMMU_FEAT_TRANS_S1) ||
>> +	     !(smmu->features & ARM_SMMU_FEAT_TRANS_S2))) {
>> +		dev_info(smmu_domain->smmu->dev,
>> +			 "does not implement two stages\n");
>> +		return -EINVAL;
>> +	}
>> +
>>  	/* Restrict the stage to what we can actually support */
>>  	if (!(smmu->features & ARM_SMMU_FEAT_TRANS_S1))
>>  		smmu_domain->stage = ARM_SMMU_DOMAIN_S2;
>> diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
>> index 07f59252dd21..269779dee8d1 100644
>> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
>> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
>> @@ -206,6 +206,7 @@
>>  #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
>> @@ -682,6 +683,7 @@ struct arm_smmu_domain {
>>  	enum arm_smmu_domain_stage	stage;
>>  	struct arm_smmu_s1_cfg	s1_cfg;
>>  	struct arm_smmu_s2_cfg	s2_cfg;
>> +	bool				abort;
>>  
>>  	struct iommu_domain		domain;
> 
> Thanks,
> 
> Kunkun Jiang
>