linux-kernel - Re: [PATCH v7 13/13] Documentation: userspace-api: iommufd: Update vIOMMU

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <8f6cdd11-3bd3-4c4c-9424-c0d52eaa6f93@intel.com>
Date: Thu, 14 Nov 2024 11:13:00 +0800
From: Yi Liu <yi.l.liu@...el.com>
To: Nicolin Chen <nicolinc@...dia.com>
CC: <jgg@...dia.com>, <kevin.tian@...el.com>, <corbet@....net>,
	<joro@...tes.org>, <suravee.suthikulpanit@....com>, <will@...nel.org>,
	<robin.murphy@....com>, <dwmw2@...radead.org>, <shuah@...nel.org>,
	<iommu@...ts.linux.dev>, <linux-doc@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <linux-kselftest@...r.kernel.org>,
	<baolu.lu@...ux.intel.com>, <eric.auger@...hat.com>,
	<jean-philippe@...aro.org>, <mdf@...nel.org>, <mshavit@...gle.com>,
	<shameerali.kolothum.thodi@...wei.com>, <smostafa@...gle.com>, <aik@....com>,
	<zhangfei.gao@...aro.org>, <patches@...ts.linux.dev>
Subject: Re: [PATCH v7 13/13] Documentation: userspace-api: iommufd: Update
 vIOMMU

On 2024/11/14 08:18, Nicolin Chen wrote:
> On Tue, Nov 12, 2024 at 09:15:02PM +0800, Yi Liu wrote:
>> On 2024/11/6 04:04, Nicolin Chen wrote:
>>> +5. IOMMUFD_OBJ_VIOMMU can be only manually created via the IOMMU_VIOMMU_ALLOC
>>> +   uAPI, provided a dev_id (for the device's physical IOMMU to back the vIOMMU)
>>> +   and an hwpt_id (to associate the vIOMMU to a nesting parent HWPT_PAGING). The
>>> +   iommufd core will link the vIOMMU object to the struct iommu_device that the
>>> +   struct device is behind.
>>
>> It looks to be reasonable to share the viommu_obj between devices behind
>> the same physical IOMMU. This design seems no enforcement for it. So it's
>> all up to userspace from what I got. :)
> 
> It enforces at the vDEVICE allocation:
> 	if (viommu->iommu_dev != __iommu_get_iommu_dev(idev->dev)) {
> 		return -EINVAL;

this matches the device and the viommu.

> 
> Yet, assuming you are referring to creating two vIOMMUs per VM for
> two devices behind the same IOMMU (?), there is no enforcement..

right, but not limited to two vIOMMUs as the viommu_obj is not instanced
per vIOMMUs.

> The suggested way for VMM, just like two devices sharing the same
> s2 parent hwpt, is to share the vIOMMU object.

so the user would try to create vDevices with a given viommu_obj until
failure, then it would allocate another viommu_obj for the failed device.
is it? sounds reasonable.

-- 
Regards,
Yi Liu