linux-kernel - Re: [PATCH v2 06/19] iommufd/viommu: Add IOMMU_VIOMMU_SET/UNSET_VDEV

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Message-ID: <76ac7908-45d7-4821-b34c-a5d2ee49c7d7@amd.com>
Date: Fri, 9 May 2025 12:57:18 +1000
From: Alexey Kardashevskiy <aik@....com>
To: Jason Gunthorpe <jgg@...dia.com>
Cc: Nicolin Chen <nicolinc@...dia.com>, kevin.tian@...el.com,
 will@...nel.org, joro@...tes.org, suravee.suthikulpanit@....com,
 robin.murphy@....com, dwmw2@...radead.org, baolu.lu@...ux.intel.com,
 shuah@...nel.org, linux-kernel@...r.kernel.org, iommu@...ts.linux.dev,
 linux-arm-kernel@...ts.infradead.org, linux-kselftest@...r.kernel.org,
 eric.auger@...hat.com, jean-philippe@...aro.org, mdf@...nel.org,
 mshavit@...gle.com, shameerali.kolothum.thodi@...wei.com,
 smostafa@...gle.com, yi.l.liu@...el.com
Subject: Re: [PATCH v2 06/19] iommufd/viommu: Add
 IOMMU_VIOMMU_SET/UNSET_VDEV_ID ioctl



On 7/5/25 22:24, Jason Gunthorpe wrote:
> On Wed, May 07, 2025 at 09:18:29PM +1000, Alexey Kardashevskiy wrote:
> 
>>> We should not destroy the vdevice for something like that. In a CC
>>> case that would unplug it from the VM which is not right.
>>
>> vdevice is not directly seen by the guest, is not it? The guest will
>> see, for example, an "AMD IOMMU" and assume there is device table
>> for all 64K devices, and so on, it is QEMU which will be
>> reallocating vdevice in the host's IOMMUFD. Did I miss something
>> here? Thanks,
> 
> I imagined the vdevice would trigger the CC call to create the vPCI
> function in the guest attached to the secure iommu.

What is this vPCI going to look like inside the guest? There still be AMD IOMMU PCI function and passed through to-be-trusted PCI function.

> At least some
> arches will need something like that.
> 
> The "AMD IOMMU" I expected to be created by the viommu object.

Right.

-- 
Alexey