linux-kernel - RE: [PATCH v2 04/19] iommufd: Allow pt_id to carry viommu_id for IOMMU_HWPT

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: <BN9PR11MB52763F8856FE20ACACDDCCE68C6B2@BN9PR11MB5276.namprd11.prod.outlook.com>
Date: Fri, 27 Sep 2024 00:43:16 +0000
From: "Tian, Kevin" <kevin.tian@...el.com>
To: Nicolin Chen <nicolinc@...dia.com>, "Liu, Yi L" <yi.l.liu@...el.com>
CC: "jgg@...dia.com" <jgg@...dia.com>, "will@...nel.org" <will@...nel.org>,
	"joro@...tes.org" <joro@...tes.org>, "suravee.suthikulpanit@....com"
	<suravee.suthikulpanit@....com>, "robin.murphy@....com"
	<robin.murphy@....com>, "dwmw2@...radead.org" <dwmw2@...radead.org>,
	"baolu.lu@...ux.intel.com" <baolu.lu@...ux.intel.com>, "shuah@...nel.org"
	<shuah@...nel.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "iommu@...ts.linux.dev"
	<iommu@...ts.linux.dev>, "linux-arm-kernel@...ts.infradead.org"
	<linux-arm-kernel@...ts.infradead.org>, "linux-kselftest@...r.kernel.org"
	<linux-kselftest@...r.kernel.org>, "eric.auger@...hat.com"
	<eric.auger@...hat.com>, "jean-philippe@...aro.org"
	<jean-philippe@...aro.org>, "mdf@...nel.org" <mdf@...nel.org>,
	"mshavit@...gle.com" <mshavit@...gle.com>,
	"shameerali.kolothum.thodi@...wei.com"
	<shameerali.kolothum.thodi@...wei.com>, "smostafa@...gle.com"
	<smostafa@...gle.com>
Subject: RE: [PATCH v2 04/19] iommufd: Allow pt_id to carry viommu_id for
 IOMMU_HWPT_ALLOC

> From: Nicolin Chen <nicolinc@...dia.com>
> Sent: Friday, September 27, 2024 4:11 AM
> 
> On Thu, Sep 26, 2024 at 04:50:46PM +0800, Yi Liu wrote:
> > On 2024/8/28 00:59, Nicolin Chen wrote:
> > > Now a VIOMMU can wrap a shareable nested parent HWPT. So, it can act
> like
> > > a nested parent HWPT to allocate a nested HWPT.
> > >
> > > Support that in the IOMMU_HWPT_ALLOC ioctl handler, and update its
> kdoc.
> > >
> > > Also, associate a viommu to an allocating nested HWPT.
> >
> > it still not quite clear to me what vIOMMU obj stands for. Here, it is a
> > wrapper of s2 hpwt IIUC. But in the cover letter, vIOMMU obj can instanced
> > per the vIOMMU units in VM.
> 
> Yea, the implementation in this version is merely a wrapper. I
> had a general introduction of vIOMMU in the other reply. And I
> will put something similar in the next version of the series,
> so the idea would be bigger than a wrapper.
> 
> > Does it mean each vIOMMU of VM can only have
> > one s2 HWPT?
> 
> Giving some examples here:
>  - If a VM has 1 vIOMMU, there will be 1 vIOMMU object in the
>    kernel holding one S2 HWPT.
>  - If a VM has 2 vIOMMUs, there will be 2 vIOMMU objects in the
>    kernel that can hold two different S2 HWPTs, or share one S2
>    HWPT (saving memory).
> 

this is not consistent with previous discussion.

even for 1 vIOMMU per VM there could be multiple vIOMMU objects
created in the kernel in case the devices connected to the VM-visible
vIOMMU locate behind different physical SMMUs.

we don't expect one vIOMMU object to span multiple physical ones.