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Re: [PATCH 19/30] panic: Add the panic hypervisor notifier list
- To: "Guilherme G. Piccoli" <gpiccoli@xxxxxxxxxx>
- From: Petr Mladek <pmladek@xxxxxxxx>
- Date: Tue, 24 May 2022 10:04:51 +0200
- Cc: Scott Branden <scott.branden@xxxxxxxxxxxx>, Sebastian Reichel <sre@xxxxxxxxxx>, Florian Fainelli <f.fainelli@xxxxxxxxx>, Desmond yan <desmond.yan@xxxxxxxxxxxx>, David Gow <davidgow@xxxxxxxxxx>, Evan Green <evgreen@xxxxxxxxxxxx>, Julius Werner <jwerner@xxxxxxxxxxxx>, bcm-kernel-feedback-list@xxxxxxxxxxxx, linux-pm@xxxxxxxxxxxxxxx, akpm@xxxxxxxxxxxxxxxxxxxx, bhe@xxxxxxxxxx, kexec@xxxxxxxxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, linuxppc-dev@xxxxxxxxxxxxxxxx, linux-alpha@xxxxxxxxxxxxxxx, linux-arm-kernel@xxxxxxxxxxxxxxxxxxx, linux-edac@xxxxxxxxxxxxxxx, linux-hyperv@xxxxxxxxxxxxxxx, linux-leds@xxxxxxxxxxxxxxx, linux-mips@xxxxxxxxxxxxxxx, linux-parisc@xxxxxxxxxxxxxxx, linux-remoteproc@xxxxxxxxxxxxxxx, linux-s390@xxxxxxxxxxxxxxx, linux-tegra@xxxxxxxxxxxxxxx, linux-um@xxxxxxxxxxxxxxxxxxx, linux-xtensa@xxxxxxxxxxxxxxxx, netdev@xxxxxxxxxxxxxxx, openipmi-developer@xxxxxxxxxxxxxxxxxxxxx, rcu@xxxxxxxxxxxxxxx, sparclinux@xxxxxxxxxxxxxxx, xen-devel@xxxxxxxxxxxxxxxxxxxx, x86@xxxxxxxxxx, kernel-dev@xxxxxxxxxx, kernel@xxxxxxxxxxxx, halves@xxxxxxxxxxxxx, fabiomirmar@xxxxxxxxx, alejandro.j.jimenez@xxxxxxxxxx, andriy.shevchenko@xxxxxxxxxxxxxxx, arnd@xxxxxxxx, bp@xxxxxxxxx, corbet@xxxxxxx, d.hatayama@xxxxxxxxxxxxxx, dave.hansen@xxxxxxxxxxxxxxx, dyoung@xxxxxxxxxx, feng.tang@xxxxxxxxx, gregkh@xxxxxxxxxxxxxxxxxxx, mikelley@xxxxxxxxxxxxx, hidehiro.kawai.ez@xxxxxxxxxxx, jgross@xxxxxxxx, john.ogness@xxxxxxxxxxxxx, keescook@xxxxxxxxxxxx, luto@xxxxxxxxxx, mhiramat@xxxxxxxxxx, mingo@xxxxxxxxxx, paulmck@xxxxxxxxxx, peterz@xxxxxxxxxxxxx, rostedt@xxxxxxxxxxx, senozhatsky@xxxxxxxxxxxx, stern@xxxxxxxxxxxxxxxxxxx, tglx@xxxxxxxxxxxxx, vgoyal@xxxxxxxxxx, vkuznets@xxxxxxxxxx, will@xxxxxxxxxx, Alexander Gordeev <agordeev@xxxxxxxxxxxxx>, Andrea Parri <parri.andrea@xxxxxxxxx>, Ard Biesheuvel <ardb@xxxxxxxxxx>, Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>, Brian Norris <computersforpeace@xxxxxxxxx>, Christian Borntraeger <borntraeger@xxxxxxxxxxxxx>, Christophe JAILLET <christophe.jaillet@xxxxxxxxxx>, "David S. Miller" <davem@xxxxxxxxxxxxx>, Dexuan Cui <decui@xxxxxxxxxxxxx>, Doug Berger <opendmb@xxxxxxxxx>, Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>, Hari Bathini <hbathini@xxxxxxxxxxxxx>, Heiko Carstens <hca@xxxxxxxxxxxxx>, Justin Chen <justinpopo6@xxxxxxxxx>, "K. Y. Srinivasan" <kys@xxxxxxxxxxxxx>, Lee Jones <lee.jones@xxxxxxxxxx>, Markus Mayer <mmayer@xxxxxxxxxxxx>, Michael Ellerman <mpe@xxxxxxxxxxxxxx>, Mihai Carabas <mihai.carabas@xxxxxxxxxx>, Nicholas Piggin <npiggin@xxxxxxxxx>, Paul Mackerras <paulus@xxxxxxxxx>, Pavel Machek <pavel@xxxxxx>, Shile Zhang <shile.zhang@xxxxxxxxxxxxxxxxx>, Stephen Hemminger <sthemmin@xxxxxxxxxxxxx>, Sven Schnelle <svens@xxxxxxxxxxxxx>, Thomas Bogendoerfer <tsbogend@xxxxxxxxxxxxxxxx>, Tianyu Lan <Tianyu.Lan@xxxxxxxxxxxxx>, Vasily Gorbik <gor@xxxxxxxxxxxxx>, Wang ShaoBo <bobo.shaobowang@xxxxxxxxxx>, Wei Liu <wei.liu@xxxxxxxxxx>, zhenwei pi <pizhenwei@xxxxxxxxxxxxx>
- Delivery-date: Tue, 24 May 2022 08:04:56 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On Mon 2022-05-23 11:56:12, Guilherme G. Piccoli wrote:
> On 19/05/2022 16:20, Scott Branden wrote:
> > [...]
> >> Hi Scott / Desmond, thanks for the detailed answer! Is this adapter
> >> designed to run in x86 only or you have other architectures' use cases?
> > The adapter may be used in any PCIe design that supports DMA.
> > So it may be possible to run in arm64 servers.
> >>
> >> [...]
> >> With that said, and given this is a lightweight notifier that ideally
> >> should run ASAP, I'd keep this one in the hypervisor list. We can
> >> "adjust" the semantic of this list to include lightweight notifiers that
> >> reset adapters.
> > Sounds the best to keep system operating as tested today.
> >>
> >> With that said, Petr has a point - not always such list is going to be
> >> called before kdump. So, that makes me think in another idea: what if we
> >> have another list, but not on panic path, but instead in the custom
> >> crash_shutdown()? Drivers could add callbacks there that must execute
> >> before kexec/kdump, no matter what.
> > It may be beneficial for some other drivers but for our use we would
> > then need to register for the panic path and the crash_shutdown path.
> > We notify the VK card for 2 purposes: one to stop DMA so memory stop
> > changing during a kdump. And also to get the card into a good state so
> > resets happen cleanly.
>
> Thanks Scott! With that, I guess it's really better to keep this
> notifier in this hypervisor/early list - I'm planning to do that for V2.
> Unless Petr or somebody has strong feelings against that, of course.
I am fine with it because we do not have a better solution at the
moment.
It might be a good candidate for the 5th notifier list mentioned
in the thread https://lore.kernel.org/r/YoyQyHHfhIIXSX0U@alley .
But I am not sure if the 5th list is worth the complexity.
Best Regards,
Petr
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