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.
WARNING: multiple messages have this Message-ID (diff)
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
next prev parent reply other threads:[~2023-07-03 16:38 UTC|newest]
Thread overview: 12+ 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 12:50 ` Kristina Martsenko
2023-07-01 17:42 ` Oliver Upton
2023-07-01 17:42 ` Oliver Upton
2023-07-03 9:45 ` Marc Zyngier
2023-07-03 9:45 ` Marc Zyngier
2023-07-03 10:36 ` Kristina Martsenko
2023-07-03 10:36 ` Kristina Martsenko
2023-07-03 16:02 ` Oliver Upton
2023-07-03 16:02 ` Oliver Upton
2023-07-03 16:38 ` Marc Zyngier [this message]
2023-07-03 16:38 ` Marc Zyngier
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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.