linux-kernel - RE: [RFC 11/20] iommu/iommufd: Add IOMMU_IOASID

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: <BN9PR11MB5433C0D532DA55D4584216A08CB79@BN9PR11MB5433.namprd11.prod.outlook.com>
Date:   Wed, 13 Oct 2021 07:14:54 +0000
From:   "Tian, Kevin" <kevin.tian@...el.com>
To:     Jean-Philippe Brucker <jean-philippe@...aro.org>,
        Jason Gunthorpe <jgg@...dia.com>
CC:     David Gibson <david@...son.dropbear.id.au>,
        "Liu, Yi L" <yi.l.liu@...el.com>,
        "alex.williamson@...hat.com" <alex.williamson@...hat.com>,
        "hch@....de" <hch@....de>,
        "jasowang@...hat.com" <jasowang@...hat.com>,
        "joro@...tes.org" <joro@...tes.org>,
        "parav@...lanox.com" <parav@...lanox.com>,
        "lkml@...ux.net" <lkml@...ux.net>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "lushenming@...wei.com" <lushenming@...wei.com>,
        "eric.auger@...hat.com" <eric.auger@...hat.com>,
        "corbet@....net" <corbet@....net>,
        "Raj, Ashok" <ashok.raj@...el.com>,
        "yi.l.liu@...ux.intel.com" <yi.l.liu@...ux.intel.com>,
        "Tian, Jun J" <jun.j.tian@...el.com>, "Wu, Hao" <hao.wu@...el.com>,
        "Jiang, Dave" <dave.jiang@...el.com>,
        "jacob.jun.pan@...ux.intel.com" <jacob.jun.pan@...ux.intel.com>,
        "kwankhede@...dia.com" <kwankhede@...dia.com>,
        "robin.murphy@....com" <robin.murphy@....com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        "dwmw2@...radead.org" <dwmw2@...radead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "baolu.lu@...ux.intel.com" <baolu.lu@...ux.intel.com>,
        "nicolinc@...dia.com" <nicolinc@...dia.com>
Subject: RE: [RFC 11/20] iommu/iommufd: Add IOMMU_IOASID_ALLOC/FREE

> From: Jean-Philippe Brucker <jean-philippe@...aro.org>
> Sent: Tuesday, October 12, 2021 4:34 PM
> 
> On Mon, Oct 11, 2021 at 08:38:17PM -0300, Jason Gunthorpe wrote:
> > On Mon, Oct 11, 2021 at 09:49:57AM +0100, Jean-Philippe Brucker wrote:
> >
> > > Seems like we don't need the negotiation part?  The host kernel
> > > communicates available IOVA ranges to userspace including holes (patch
> > > 17), and userspace can check that the ranges it needs are within the IOVA
> > > space boundaries. That part is necessary for DPDK as well since it needs
> > > to know about holes in the IOVA space where DMA wouldn't work as
> expected
> > > (MSI doorbells for example).
> >
> > I haven't looked super closely at DPDK, but the other simple VFIO app
> > I am aware of struggled to properly implement this semantic (Indeed it
> > wasn't even clear to the author this was even needed).
> >
> > It requires interval tree logic inside the application which is not a
> > trivial algorithm to implement in C.
> >
> > I do wonder if the "simple" interface should have an option more like
> > the DMA API where userspace just asks to DMA map some user memory
> and
> > gets back the dma_addr_t to use. Kernel manages the allocation
> > space/etc.
> 
> Agreed, it's tempting to use IOVA = VA but the two spaces aren't
> necessarily compatible. An extension that plugs into the IOVA allocator
> could be useful to userspace drivers.
> 

Make sense. We can have a flag in IOMMUFD_MAP_DMA to tell whether
the user provides vaddr or expects the kernel to allocate and return.

Thanks
Kevin