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

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Message-ID: <CABeXuvrYzLoc7YGtmXDJqEovwyERbndN4cC6UaYAw5+qABRr8A@mail.gmail.com>
Date:   Sun, 10 Nov 2019 12:36:49 -0800
From:   Deepa Dinamani <deepa.kernel@...il.com>
To:     "Zeng, Jason" <jason.zeng@...el.com>
Cc:     David Woodhouse <dwmw2@...radead.org>,
        "joro@...tes.org" <joro@...tes.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        "Tian, Kevin" <kevin.tian@...el.com>,
        Arnd Bergmann <arnd@...db.de>, rminnich@...gle.com
Subject: Re: [PATCH] intel-iommu: Turn off translations at shutdown

On Sun, Nov 10, 2019 at 10:24 AM Deepa Dinamani <deepa.kernel@...il.com> wrote:
>
> On Fri, Nov 8, 2019 at 2:48 PM Deepa Dinamani <deepa.kernel@...il.com> wrote:
> >
> > > > > 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!
> >
> > Are these changes already part of the kernel like avoiding shutdown of
> > the passthrough devices? device_shutdown() doesn't seem to be doing
> > anything selectively as of now.
>
> I've posted the v2 without the conditional for now:
> https://lore.kernel.org/patchwork/patch/1151225/
>
> As a side topic, I'm trying to support https://www.linuxboot.org/. I
> have a couple of more such cleanups coming. The VMM live updates and
> linuxboot seem to have contradicting requirements and they both use
> kexec. So kexec_in_progress doesn't seem like a sufficient indicator
> to distinguish between the two. Do you already have an idea on how to
> distiguish between them? Does a separate sys_reboot() command
> parameter sound ok? Or, we could use the flags in the sys_kexec_load()
> depending on how the live update feature is implemented.

Also, the AMD driver disables iommu at shutdown already. So the live
update feature is already broken on AMD.

-Deepa