linux-kernel - Re: [PATCH V4 05/18] iommu/ioasid: Redefine IOASID set and allocation APIs

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: <20210507151511.612d1424@jacob-builder>
Date:   Fri, 7 May 2021 15:15:11 -0700
From:   Jacob Pan <jacob.jun.pan@...ux.intel.com>
To:     Jason Gunthorpe <jgg@...dia.com>
Cc:     "Raj, Ashok" <ashok.raj@...el.com>,
        Jean-Philippe Brucker <jean-philippe@...aro.org>,
        "Tian, Kevin" <kevin.tian@...el.com>,
        Alex Williamson <alex.williamson@...hat.com>,
        "Liu, Yi L" <yi.l.liu@...el.com>,
        Auger Eric <eric.auger@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Joerg Roedel <joro@...tes.org>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        David Woodhouse <dwmw2@...radead.org>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        "cgroups@...r.kernel.org" <cgroups@...r.kernel.org>,
        Tejun Heo <tj@...nel.org>,
        Johannes Weiner <hannes@...xchg.org>,
        Jean-Philippe Brucker <jean-philippe@...aro.com>,
        Jonathan Corbet <corbet@....net>, "Wu, Hao" <hao.wu@...el.com>,
        "Jiang, Dave" <dave.jiang@...el.com>, jacob.jun.pan@...ux.intel.com
Subject: Re: [PATCH V4 05/18] iommu/ioasid: Redefine IOASID set and
 allocation APIs

Hi Jason,

On Fri, 7 May 2021 16:28:10 -0300, Jason Gunthorpe <jgg@...dia.com> wrote:

> > The unanswered question is how do we plumb from vIOMMU without a custom
> > allocator to get a system wide PASID?   
> 
> PASID allocation is part of the iommu driver, it really shouldn't be
> global.
> 
In the current code, the pluggable custom allocator *is* part of the iommu
vendor driver. If it decides the allocation is global then it should be
suitable for the platform since there will never be a VT-d IOMMU on another
vendor's platform.

It is true that the default allocator is global which suites the current
needs. I am just wondering if we are solving a problem does not exist yet.

> When the architecture code goes to allocate a single PASID for the
> mm_struct it should flag that allocation request with a 'must work for
> all RIDs flag' and the iommu driver should take care of it. That might
> mean the iommu driver consults a global static xarray, or maybe it
> does a hypercall, but it should be done through that API, not a side
> care global singleton.
Why do we need to flag the allocation every time if on a platform *every*
PASID can potentially be global? At the time of allocation, we don't know
if the PASID will be used for a shared (ENQCMD) or a dedicated workqueue.

Thanks,

Jacob