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

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Message-ID: <CABeXuvqMpXbSNasET4-u16Hrj710fe-V706tsFZhOTJoir8Xjw@mail.gmail.com>
Date:   Sun, 10 Nov 2019 10:24:19 -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>,
        Ron Minnich <rminnich@...dia.gov>,
        Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH] intel-iommu: Turn off translations at shutdown

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.

-Deepa