linux-kernel - Re: [PATCH v14 13/13] iommu/smmuv3: Accept configs with more than one context descriptor

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Date:   Thu, 1 Apr 2021 13:48:44 +0200
From:   Auger Eric <eric.auger@...hat.com>
To:     Zenghui Yu <yuzenghui@...wei.com>
Cc:     eric.auger.pro@...il.com, iommu@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        kvmarm@...ts.cs.columbia.edu, will@...nel.org, maz@...nel.org,
        robin.murphy@....com, joro@...tes.org, alex.williamson@...hat.com,
        tn@...ihalf.com, zhukeqian1@...wei.com,
        jacob.jun.pan@...ux.intel.com, yi.l.liu@...el.com,
        wangxingang5@...wei.com, jiangkunkun@...wei.com,
        jean-philippe@...aro.org, zhangfei.gao@...aro.org,
        zhangfei.gao@...il.com, vivek.gautam@....com,
        shameerali.kolothum.thodi@...wei.com, nicoleotsuka@...il.com,
        lushenming@...wei.com, vsethi@...dia.com,
        wanghaibin.wang@...wei.com
Subject: Re: [PATCH v14 13/13] iommu/smmuv3: Accept configs with more than one
 context descriptor

Hi Zenghui,

On 3/30/21 11:23 AM, Zenghui Yu wrote:
> Hi Eric,
> 
> On 2021/2/24 4:56, Eric Auger wrote:
>> In preparation for vSVA, let's accept userspace provided configs
>> with more than one CD. We check the max CD against the host iommu
>> capability and also the format (linear versus 2 level).
>>
>> Signed-off-by: Eric Auger <eric.auger@...hat.com>
>> Signed-off-by: Shameer Kolothum <shameerali.kolothum.thodi@...wei.com>
>> ---
>>   drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 13 ++++++++-----
>>   1 file changed, 8 insertions(+), 5 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 332d31c0680f..ab74a0289893 100644
>> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
>> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
>> @@ -3038,14 +3038,17 @@ static int arm_smmu_attach_pasid_table(struct
>> iommu_domain *domain,
>>           if (smmu_domain->s1_cfg.set)
>>               goto out;
>>   -        /*
>> -         * we currently support a single CD so s1fmt and s1dss
>> -         * fields are also ignored
>> -         */
>> -        if (cfg->pasid_bits)
>> +        list_for_each_entry(master, &smmu_domain->devices,
>> domain_head) {
>> +            if (cfg->pasid_bits > master->ssid_bits)
>> +                goto out;
>> +        }
>> +        if (cfg->vendor_data.smmuv3.s1fmt ==
>> STRTAB_STE_0_S1FMT_64K_L2 &&
>> +                !(smmu->features & ARM_SMMU_FEAT_2_LVL_CDTAB))
>>               goto out;
>>             smmu_domain->s1_cfg.cdcfg.cdtab_dma = cfg->base_ptr;
>> +        smmu_domain->s1_cfg.s1cdmax = cfg->pasid_bits;
>> +        smmu_domain->s1_cfg.s1fmt = cfg->vendor_data.smmuv3.s1fmt;
> 
> And what about the SIDSS field?
> 
I added this patch upon Shameer's request, to be more vSVA friendly.
Hower this series does not really target multiple CD support. At the
moment the driver only supports STRTAB_STE_1_S1DSS_SSID0 (0x2) I think.
At this moment maybe I can only check the s1dss field is 0x2. Or simply
removes this patch?

Thoughts?

Eric