linux-kernel - Re: [PATCH v4 09/12] iommu/vt-d: Add iotlb flush for nested domain

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Date:   Thu, 3 Aug 2023 11:24:40 +0800
From:   Baolu Lu <baolu.lu@...ux.intel.com>
To:     "Tian, Kevin" <kevin.tian@...el.com>,
        "Liu, Yi L" <yi.l.liu@...el.com>,
        "joro@...tes.org" <joro@...tes.org>,
        "alex.williamson@...hat.com" <alex.williamson@...hat.com>,
        "jgg@...dia.com" <jgg@...dia.com>,
        "robin.murphy@....com" <robin.murphy@....com>
Cc:     baolu.lu@...ux.intel.com, "cohuck@...hat.com" <cohuck@...hat.com>,
        "eric.auger@...hat.com" <eric.auger@...hat.com>,
        "nicolinc@...dia.com" <nicolinc@...dia.com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "mjrosato@...ux.ibm.com" <mjrosato@...ux.ibm.com>,
        "chao.p.peng@...ux.intel.com" <chao.p.peng@...ux.intel.com>,
        "yi.y.sun@...ux.intel.com" <yi.y.sun@...ux.intel.com>,
        "peterx@...hat.com" <peterx@...hat.com>,
        "jasowang@...hat.com" <jasowang@...hat.com>,
        "shameerali.kolothum.thodi@...wei.com" 
        <shameerali.kolothum.thodi@...wei.com>,
        "lulu@...hat.com" <lulu@...hat.com>,
        "suravee.suthikulpanit@....com" <suravee.suthikulpanit@....com>,
        "iommu@...ts.linux.dev" <iommu@...ts.linux.dev>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-kselftest@...r.kernel.org" <linux-kselftest@...r.kernel.org>,
        "Duan, Zhenzhong" <zhenzhong.duan@...el.com>
Subject: Re: [PATCH v4 09/12] iommu/vt-d: Add iotlb flush for nested domain

On 2023/8/2 15:46, Tian, Kevin wrote:
>> From: Liu, Yi L <yi.l.liu@...el.com>
>> Sent: Monday, July 24, 2023 7:14 PM
>>
>> +static int intel_nested_cache_invalidate_user(struct iommu_domain
>> *domain,
>> +					      void *user_data)
>> +{
>> +	struct iommu_hwpt_vtd_s1_invalidate_desc *req = user_data;
>> +	struct iommu_hwpt_vtd_s1_invalidate *inv_info = user_data;
>> +	struct dmar_domain *dmar_domain = to_dmar_domain(domain);
>> +	unsigned int entry_size = inv_info->entry_size;
>> +	u64 uptr = inv_info->inv_data_uptr;
>> +	u64 nr_uptr = inv_info->entry_nr_uptr;
>> +	struct device_domain_info *info;
>> +	u32 entry_nr, index;
>> +	unsigned long flags;
>> +	int ret = 0;
>> +
>> +	if (get_user(entry_nr, (uint32_t __user *)u64_to_user_ptr(nr_uptr)))
>> +		return -EFAULT;
>> +
>> +	for (index = 0; index < entry_nr; index++) {
>> +		ret = copy_struct_from_user(req, sizeof(*req),
>> +					    u64_to_user_ptr(uptr + index *
>> entry_size),
>> +					    entry_size);
> 
> If continuing this direction then the driver should also check minsz etc.
> for struct iommu_hwpt_vtd_s1_invalidate and iommu_hwpt_vtd_s1_invalidate_desc
> since they are uAPI and subject to change.

Agreed.

> 
>> +		if (ret) {
>> +			pr_err_ratelimited("Failed to fetch invalidation
>> request\n");
>> +			break;
>> +		}
>> +
>> +		if (req->__reserved || (req->flags &
>> ~IOMMU_VTD_QI_FLAGS_LEAF) ||
>> +		    !IS_ALIGNED(req->addr, VTD_PAGE_SIZE)) {
>> +			ret = -EINVAL;
>> +			break;
>> +		}
>> +
>> +		spin_lock_irqsave(&dmar_domain->lock, flags);
>> +		list_for_each_entry(info, &dmar_domain->devices, link)
>> +			intel_nested_invalidate(info->dev, dmar_domain,
>> +						req->addr, req->npages);
>> +		spin_unlock_irqrestore(&dmar_domain->lock, flags);
> 
> Disabling interrupt while invalidating iotlb is certainly unacceptable.
> 
> Actually there is no need to walk devices. Under dmar_domain there
> is already a list of attached iommu's.

Walking device is only necessary when invalidating device TLB. For iotlb
invalidation, it only needs to know the iommu's.

Best regards,
baolu