linux-kernel - Re: [PATCH v4 12/12] iommu/vt-d: Disallow nesting on domains with read-only mappings

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Message-ID: <b099a333-65b1-de9e-742d-d12f4fb58f67@linux.intel.com>
Date:   Thu, 3 Aug 2023 11:27:01 +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 12/12] iommu/vt-d: Disallow nesting on domains with
 read-only mappings

On 2023/8/2 15:59, Tian, Kevin wrote:
>> From: Liu, Yi L <yi.l.liu@...el.com>
>> Sent: Monday, July 24, 2023 7:14 PM
>>
>> @@ -2147,6 +2148,18 @@ __domain_mapping(struct dmar_domain
>> *domain, unsigned long iov_pfn,
>>   	if ((prot & (DMA_PTE_READ|DMA_PTE_WRITE)) == 0)
>>   		return -EINVAL;
>>
>> +	if (!(prot & DMA_PTE_WRITE) && !domain->read_only_mapped) {
>> +		spin_lock_irqsave(&domain->lock, flags);
>> +		if (domain->set_nested) {
>> +			pr_err_ratelimited("No read-only mapping
>> permitted\n");
> 
> "Read-only mapping is disallowed on the domain which serves as the
> parent in a nested configuration, due to HW errata (ERRATA_772415_SPR17)"

Ack.

> 
>> +	u8 read_only_mapped:1;		/* domain has mappings with
>> read-only
>> +					 * permission.
>> +					 */
>> +	u8 set_nested:1;		/* has other domains nested on it */
> 
> what about "is_parent"?

"is_parent" is still a bit generic. How about "is_nested_parent"?

> 
>>
>> +	spin_lock_irqsave(&s2_dmar_domain->lock, flags);
>> +	if (s2_dmar_domain->read_only_mapped) {
>> +		spin_unlock_irqrestore(&s2_dmar_domain->lock, flags);
>> +		pr_err_ratelimited("S2 domain has read-only mappings\n");
> 
> "Nested configuration is disallowed when the stage-2 domain already
> has read-only mappings, due to HW errata (ERRATA_772415_SPR17)"

Ack.

Best regards,
baolu