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

Auger Eric
2021-04-01T13:20:48Z

Hi Shameer,
On 4/1/21 2:38 PM, Shameerali Kolothum Thodi wrote:
>
>
>> -----Original Message-----
>> From: Auger Eric [mailto:eric.auger@redhat.com]
>> Sent: 01 April 2021 12:49
>> To: yuzenghui <yuzenghui@huawei.com>
>> Cc: 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; maz@kernel.org;
>> robin.murphy@arm.com; joro@8bytes.org; alex.williamson@redhat.com;
>> tn@semihalf.com; zhukeqian <zhukeqian1@huawei.com>;
>> jacob.jun.pan@linux.intel.com; yi.l.liu@intel.com; wangxingang
>> <wangxingang5@huawei.com>; jiangkunkun <jiangkunkun@huawei.com>;
>> jean-philippe@linaro.org; zhangfei.gao@linaro.org; zhangfei.gao@gmail.com;
>> vivek.gautam@arm.com; Shameerali Kolothum Thodi
>> <shameerali.kolothum.thodi@huawei.com>; nicoleotsuka@gmail.com;
>> lushenming <lushenming@huawei.com>; vsethi@nvidia.com; Wanghaibin (D)
>> <wanghaibin.wang@huawei.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@redhat.com>
>>>> Signed-off-by: Shameer Kolothum
>> <shameerali.kolothum.thodi@huawei.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?
>
> Right. This was useful for vSVA tests. But yes, to properly support multiple CDs
> we need to pass the S1DSS from Qemu. And that requires further changes.
> So I think it's better to remove this patch and reject S1CDMAX != 0 cases.
OK I will remove it

Thanks

Eric
>
> Thanks,
> Shameer
>
>>
>> Eric