linux-kernel - Re: [RFC] /dev/ioasid uAPI proposal

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: <YNwVrZoR5k3RnWeL@infradead.org>
Date:   Wed, 30 Jun 2021 07:56:45 +0100
From:   Christoph Hellwig <hch@...radead.org>
To:     "Tian, Kevin" <kevin.tian@...el.com>
Cc:     Alex Williamson <alex.williamson@...hat.com>,
        Jason Gunthorpe <jgg@...dia.com>,
        Jean-Philippe Brucker <jean-philippe@...aro.org>,
        "Jiang, Dave" <dave.jiang@...el.com>,
        "Raj, Ashok" <ashok.raj@...el.com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        Jonathan Corbet <corbet@....net>,
        David Woodhouse <dwmw2@...radead.org>,
        Jason Wang <jasowang@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Kirti Wankhede <kwankhede@...dia.com>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Robin Murphy <robin.murphy@....com>,
        David Gibson <david@...son.dropbear.id.au>
Subject: Re: [RFC] /dev/ioasid uAPI proposal

On Mon, Jun 07, 2021 at 03:25:32AM +0000, Tian, Kevin wrote:
> 
> Possibly just a naming thing, but I feel it's better to just talk about
> no-snoop or non-coherent in the uAPI. Per Intel SDM wbinvd is a
> privileged instruction. A process on the host has no privilege to 
> execute it. Only when this process holds a VM, this instruction matters
> as there are guest privilege levels. But having VFIO uAPI (which is
> userspace oriented) to explicitly deal with a CPU instruction which
> makes sense only in a virtualization context sounds a bit weird...

More importantly the Intel instructions here are super weird.
Pretty much every other architecture just has plan old cache
writeback/invalidate/writeback+invalidate instructions without all these
weird implications.