linux-kernel - Re: [RFC 3/7] iommufd: Add iommufd_device_bind

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Date:   Wed, 8 Nov 2023 15:45:17 +0800
From:   Yi Liu <yi.l.liu@...el.com>
To:     "Tian, Kevin" <kevin.tian@...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>,
        "baolu.lu@...ux.intel.com" <baolu.lu@...ux.intel.com>
CC:     "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>,
        "Martins, Joao" <joao.m.martins@...cle.com>
Subject: Re: [RFC 3/7] iommufd: Add iommufd_device_bind_pasid()

On 2023/10/10 16:19, Tian, Kevin wrote:
>> From: Liu, Yi L <yi.l.liu@...el.com>
>> Sent: Monday, October 9, 2023 4:51 PM
>>
>> +struct iommufd_device *iommufd_device_bind_pasid(struct iommufd_ctx
>> *ictx,
>> +						 struct device *dev,
>> +						 u32 pasid, u32 *id)
>> +{
>> +	struct iommufd_device *idev;
>> +	int rc;
>> +
>> +	/*
>> +	 * iommufd always sets IOMMU_CACHE because we offer no way for
>> userspace
>> +	 * to restore cache coherency.
>> +	 */
>> +	if (!device_iommu_capable(dev, IOMMU_CAP_CACHE_COHERENCY))
>> +		return ERR_PTR(-EINVAL);
>> +
>> +	/*
>> +	 * No iommu supports pasid-granular msi message today. Here we
>> +	 * just check whether the parent device can do safe interrupts.
>> +	 * Isolation between virtual devices within the parent device
>> +	 * relies on the parent driver to enforce.
>> +	 */
>> +	if (!iommufd_selftest_is_mock_dev(dev) &&
>> +	    !msi_device_has_isolated_msi(dev)) {
>> +		rc = iommufd_allow_unsafe_interrupts(dev);
>> +		if (rc)
>> +			return ERR_PTR(rc);
>> +	}
>> +
> 
> Only MemWr w/o pasid can be interpreted as an interrupt message
> then we need msi isolation to protect.

yes.

> 
> But for SIOV all MemWr's are tagged with a pasid hence can never
> trigger an interrupt. From this angle looks this check is unnecessary.

But the interrupts out from a SIOV virtual device do not have pasid (at
least today). Seems still need a check here if we consider this bind for
a SIOV virtual device just like binding a physical device.

-- 
Regards,
Yi Liu