linux-kernel - Re: [PATCH v14 05/13] iommu/smmuv3: Implement attach/detach_pasid

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Message-ID: <0769efb0-0a22-7cb1-b831-ec75845dde98@huawei.com>
Date:   Mon, 22 Mar 2021 14:23:48 +0800
From:   Keqian Zhu <zhukeqian1@...wei.com>
To:     Auger Eric <eric.auger@...hat.com>, <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>
CC:     <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>, <yuzenghui@...wei.com>,
        <nicoleotsuka@...il.com>, <lushenming@...wei.com>,
        <vsethi@...dia.com>
Subject: Re: [PATCH v14 05/13] iommu/smmuv3: Implement
 attach/detach_pasid_table

Hi Eric,

On 2021/3/19 21:15, Auger Eric wrote:
> Hi Keqian,
> 
> On 3/2/21 9:35 AM, Keqian Zhu wrote:
>> Hi Eric,
>>
>> On 2021/2/24 4:56, Eric Auger wrote:
>>> On attach_pasid_table() we program STE S1 related info set
>>> by the guest into the actual physical STEs. At minimum
>>> we need to program the context descriptor GPA and compute
>>> whether the stage1 is translated/bypassed or aborted.
>>>
>>> On detach, the stage 1 config is unset and the abort flag is
>>> unset.
>>>
>>> Signed-off-by: Eric Auger <eric.auger@...hat.com>
>>>
>> [...]
>>
>>> +
>>> +		/*
>>> +		 * we currently support a single CD so s1fmt and s1dss
>>> +		 * fields are also ignored
>>> +		 */
>>> +		if (cfg->pasid_bits)
>>> +			goto out;
>>> +
>>> +		smmu_domain->s1_cfg.cdcfg.cdtab_dma = cfg->base_ptr;
>> only the "cdtab_dma" field of "cdcfg" is set, we are not able to locate a specific cd using arm_smmu_get_cd_ptr().
>>
>> Maybe we'd better use a specialized function to fill other fields of "cdcfg" or add a sanity check in arm_smmu_get_cd_ptr()
>> to prevent calling it under nested mode?
>>
>> As now we just call arm_smmu_get_cd_ptr() during finalise_s1(), no problem found. Just a suggestion ;-)
> 
> forgive me for the delay. yes I can indeed make sure that code is not
> called in nested mode. Please could you detail why you would need to
> call arm_smmu_get_cd_ptr()?
I accidentally called this function in nested mode when verify the smmu mpam feature. :)

Yes, in nested mode, context descriptor is owned by guest, hypervisor does not need to care about its content.
Maybe we'd better give an explicit comment for arm_smmu_get_cd_ptr() to let coder pay attention to this? :)

Thanks,
Keqian

> 
> Thanks
> 
> Eric
>>
>> Thanks,
>> Keqian
>>
>>
>>> +		smmu_domain->s1_cfg.set = true;
>>> +		smmu_domain->abort = false;
>>> +		break;
>>> +	default:
>>> +		goto out;
>>> +	}
>>> +	spin_lock_irqsave(&smmu_domain->devices_lock, flags);
>>> +	list_for_each_entry(master, &smmu_domain->devices, domain_head)
>>> +		arm_smmu_install_ste_for_dev(master);
>>> +	spin_unlock_irqrestore(&smmu_domain->devices_lock, flags);
>>> +	ret = 0;
>>> +out:
>>> +	mutex_unlock(&smmu_domain->init_mutex);
>>> +	return ret;
>>> +}
>>> +
>>> +static void arm_smmu_detach_pasid_table(struct iommu_domain *domain)
>>> +{
>>> +	struct arm_smmu_domain *smmu_domain = to_smmu_domain(domain);
>>> +	struct arm_smmu_master *master;
>>> +	unsigned long flags;
>>> +
>>> +	mutex_lock(&smmu_domain->init_mutex);
>>> +
>>> +	if (smmu_domain->stage != ARM_SMMU_DOMAIN_NESTED)
>>> +		goto unlock;
>>> +
>>> +	smmu_domain->s1_cfg.set = false;
>>> +	smmu_domain->abort = false;
>>> +
>>> +	spin_lock_irqsave(&smmu_domain->devices_lock, flags);
>>> +	list_for_each_entry(master, &smmu_domain->devices, domain_head)
>>> +		arm_smmu_install_ste_for_dev(master);
>>> +	spin_unlock_irqrestore(&smmu_domain->devices_lock, flags);
>>> +
>>> +unlock:
>>> +	mutex_unlock(&smmu_domain->init_mutex);
>>> +}
>>> +
>>>  static bool arm_smmu_dev_has_feature(struct device *dev,
>>>  				     enum iommu_dev_features feat)
>>>  {
>>> @@ -2939,6 +3026,8 @@ static struct iommu_ops arm_smmu_ops = {
>>>  	.of_xlate		= arm_smmu_of_xlate,
>>>  	.get_resv_regions	= arm_smmu_get_resv_regions,
>>>  	.put_resv_regions	= generic_iommu_put_resv_regions,
>>> +	.attach_pasid_table	= arm_smmu_attach_pasid_table,
>>> +	.detach_pasid_table	= arm_smmu_detach_pasid_table,
>>>  	.dev_has_feat		= arm_smmu_dev_has_feature,
>>>  	.dev_feat_enabled	= arm_smmu_dev_feature_enabled,
>>>  	.dev_enable_feat	= arm_smmu_dev_enable_feature,
>>>
>>
> 
> .
>