linux-kernel - RE: [PATCH] intel-iommu: Turn off translations at shutdown

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]

Date:   Fri, 8 Nov 2019 09:11:24 +0000
From:   "Zeng, Jason" <jason.zeng@...el.com>
To:     David Woodhouse <dwmw2@...radead.org>,
        Deepa Dinamani <deepa.kernel@...il.com>,
        "joro@...tes.org" <joro@...tes.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        "Tian, Kevin" <kevin.tian@...el.com>,
        "Zeng, Jason" <jason.zeng@...el.com>
Subject: RE: [PATCH] intel-iommu: Turn off translations at shutdown



> -----Original Message-----
> From: David Woodhouse <dwmw2@...radead.org>
> Sent: Friday, November 8, 2019 4:57 PM
> To: Zeng, Jason <jason.zeng@...el.com>; Deepa Dinamani
> <deepa.kernel@...il.com>; joro@...tes.org; linux-kernel@...r.kernel.org
> Cc: iommu@...ts.linux-foundation.org; Tian, Kevin <kevin.tian@...el.com>
> Subject: Re: [PATCH] intel-iommu: Turn off translations at shutdown
> 
> On Fri, 2019-11-08 at 08:47 +0000, Zeng, Jason wrote:
> > > -----Original Message-----
> > > From: David Woodhouse <dwmw2@...radead.org>
> > > Sent: Friday, November 8, 2019 3:54 PM
> > > To: Deepa Dinamani <deepa.kernel@...il.com>; joro@...tes.org;
> linux-
> > > kernel@...r.kernel.org
> > > Cc: iommu@...ts.linux-foundation.org; Zeng, Jason
> <jason.zeng@...el.com>;
> > > Tian, Kevin <kevin.tian@...el.com>
> > > Subject: Re: [PATCH] intel-iommu: Turn off translations at shutdown
> > >
> > > On Thu, 2019-11-07 at 12:59 -0800, Deepa Dinamani wrote:
> > > > The intel-iommu driver assumes that the iommu state is
> > > > cleaned up at the start of the new kernel.
> > > > But, when we try to kexec boot something other than the
> > > > Linux kernel, the cleanup cannot be relied upon.
> > > > Hence, cleanup before we go down for reboot.
> > > >
> > > > Keeping the cleanup at initialization also, in case BIOS
> > > > leaves the IOMMU enabled.
> > > >
> > > > I considered turning off iommu only during kexec reboot,
> > > > but a clean shutdown seems always a good idea. But if
> > > > someone wants to make it conditional, we can do that.
> > >
> > > This is going to break things for the VMM live update scheme that Jason
> > > presented at KVM Forum, isn't it?
> > >
> > > In that case we rely on the IOMMU still operating during the
> > > transition.
> >
> > For VMM live update case, we should be able to detect and bypass
> > the shutdown that Deepa introduced here, so keep IOMMU still operating?
> 
> Is that a 'yes' to Deepa's "if someone wants to make it conditional, we
> can do that" ?

Yes, I think so. Thanks!