From: Marc Zyngier <maz@kernel.org>
To: Oliver Upton <oliver.upton@linux.dev>
Cc: Kristina Martsenko <kristina.martsenko@arm.com>,
isaku.yamahata@intel.com, seanjc@google.com, pbonzini@redhat.com,
kvmarm@lists.linux.dev, kvm@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
James Morse <james.morse@arm.com>
Subject: Re: KVM CPU hotplug notifier triggers BUG_ON on arm64
Date: Mon, 03 Jul 2023 17:38:14 +0100 [thread overview]
Message-ID: <864jmlx85l.wl-maz@kernel.org> (raw)
In-Reply-To: <ZKLxFveKKvoQs5RV@thinky-boi>
On Mon, 03 Jul 2023 17:02:30 +0100,
Oliver Upton <oliver.upton@linux.dev> wrote:
>
> Hey Marc,
>
> On Mon, Jul 03, 2023 at 10:45:26AM +0100, Marc Zyngier wrote:
> > On Sat, 01 Jul 2023 18:42:28 +0100, Oliver Upton <oliver.upton@linux.dev> wrote:
> > > Well, one way to hack around the problem would be to just cram
> > > preempt_{disable,enable}() into kvm_arch_hardware_disable(), but that's
> > > kinda gross in the context of cpuhp which isn't migratable in the first
> > > place. Let me have a look...
>
> Heh, I should've mentioned I'm on holiday until Thursday.
No problem, happy to keep an eye on stuff in the meantime.
>
> > An alternative would be to replace the preemptible() checks with a one
> > that looks at the migration state, but I'm not sure that's much better
> > (it certainly looks more costly).
> >
> > There is also the fact that most of our per-CPU accessors are already
> > using preemption disabling, and this code has a bunch of them. So I'm
> > not sure there is a lot to be gained from not disabling preemption
> > upfront.
> >
> > Anyway, as I was able to reproduce the issue under NV, I tested the
> > hack below. If anything, I expect it to be a reasonable fix for
> > 6.3/6.4, and until we come up with a better approach.
>
> Yeah, I'm fine with a hack like this. Do you want to send this out as a
> patch?
Now sent as 20230703163548.1498943-1-maz@kernel.org.
Enjoy your time off!
M.
--
Without deviation from the norm, progress is not possible.
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
prev parent reply other threads:[~2023-07-03 16:38 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-07-01 12:50 KVM CPU hotplug notifier triggers BUG_ON on arm64 Kristina Martsenko
2023-07-01 17:42 ` Oliver Upton
2023-07-03 9:45 ` Marc Zyngier
2023-07-03 10:36 ` Kristina Martsenko
2023-07-03 16:02 ` Oliver Upton
2023-07-03 16:38 ` Marc Zyngier [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=864jmlx85l.wl-maz@kernel.org \
--to=maz@kernel.org \
--cc=isaku.yamahata@intel.com \
--cc=james.morse@arm.com \
--cc=kristina.martsenko@arm.com \
--cc=kvm@vger.kernel.org \
--cc=kvmarm@lists.linux.dev \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=oliver.upton@linux.dev \
--cc=pbonzini@redhat.com \
--cc=seanjc@google.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).