Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Tue, 17 Jan 2023 16:27:23 +0800
From:   Baoquan He <bhe@redhat.com>
To:     Thomas Gleixner <tglx@linutronix.de>
Cc:     linux-kernel@vger.kernel.org, x86@kernel.org,
        kexec@lists.infradead.org
Subject: Re: [PATCH] Revert "x86/apic/x2apic: Implement IPI shorthands
 support"
Message-ID: <Y8Zb696MT1E1p2jZ@fedora>
References: <Y6FJgh3fOYoF0wSV@MiWiFi-R3L-srv>
 <87k01vjrnt.ffs@tglx>
 <Y7zMZ8nCNtSt09kV@fedora>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <Y7zMZ8nCNtSt09kV@fedora>
Precedence: bulk

On 01/10/23 at 10:24am, Baoquan He wrote:
> On 01/09/23 at 10:59pm, Thomas Gleixner wrote:
> > On Tue, Dec 20 2022 at 13:34, Baoquan He wrote:
> > > This reverts commit 43931d350f30c6cd8c2f498d54ef7d65750abc92.
> > >
> > > On kvm guest with 4 cpus deployed, when adding 'nr_cpus=2' to normal
> > > kernel's cmdline, and triggering crash to jump to kdump kernel, kdump
> > > kernel will stably hang. Reverting commit 43931d350f30 ("x86/apic/x2apic:
> > > Implement IPI shorthands support") can fix it.
> > 
> > Is there any output on the early console or hangs it silently?
> > 
> > If the latter, can you attach GDB to the guest and figure out where it
> > is stuck?
> 
> No any output on the ealry console. I will try gdb debugging. Thanks.

I rebase to the latest upstream kernel and tested, the stable kdump
kernel hang disappear. Seems I need do another round of bisect to see
on which commit it's made to fix that. Will update if any progress.