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Tue, 12 Aug 2025 11:17:05 +0100 Date: Tue, 12 Aug 2025 11:17:04 +0100 Message-ID: <86ms84974v.wl-maz@kernel.org> From: Marc Zyngier To: Coiby Xu Cc: Thomas Gleixner , linux-arm-kernel@lists.infradead.org, linux-pci@vger.kernel.org, kexec@lists.infradead.org Subject: Re: [Regression] kdump fails to get DHCP address unless booting with pci=nomsi or without nr_cpus=1 In-Reply-To: References: <87bjom8106.ffs@tglx> <878qjq80yu.ffs@tglx> <86v7mt9ai3.wl-maz@kernel.org> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM-LB/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL-LB/10.8 EasyPG/1.0.0 Emacs/30.1 (aarch64-unknown-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=US-ASCII X-SA-Exim-Connect-IP: 185.219.108.64 X-SA-Exim-Rcpt-To: coxu@redhat.com, tglx@linutronix.de, linux-arm-kernel@lists.infradead.org, linux-pci@vger.kernel.org, kexec@lists.infradead.org X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, 12 Aug 2025 11:09:12 +0100, Coiby Xu wrote: > > On Mon, Aug 11, 2025 at 03:52:04PM +0100, Marc Zyngier wrote: > > On Mon, 11 Aug 2025 14:03:21 +0100, > > Thomas Gleixner wrote: > >> > >> On Mon, Aug 11 2025 at 15:02, Thomas Gleixner wrote: > >> > >> CC+ Marc > >> > >> > On Mon, Aug 11 2025 at 11:23, Coiby Xu wrote: > >> >> Recently I met an issue that on certain virtual machines, the kdump > >> >> kernel fails to get DHCP IP address most of times starting from > >> >> 6.11-rc2. git bisection shows commit b5712bf89b4b ("irqchip/gic-v3-its: > >> >> Provide MSI parent for PCI/MSI[-X]") is the 1st bad commit, > >> >> > >> >> # good: [7d189c77106ed6df09829f7a419e35ada67b2bd0] PCI/MSI: Provide > >> >> # MSI_FLAG_PCI_MSI_MASK_PARENT > >> >> git bisect good 7d189c77106ed6df09829f7a419e35ada67b2bd0 > >> >> # good: [48f71d56e2b87839052d2a2ec32fc97a79c3e264] irqchip/gic-v3-its: > >> >> # Provide MSI parent infrastructure > >> >> git bisect good 48f71d56e2b87839052d2a2ec32fc97a79c3e264 > >> >> # good: [8c41ccec839c622b2d1be769a95405e4e9a4cb20] irqchip/irq-msi-lib: > >> >> # Prepare for PCI MSI/MSIX > >> >> git bisect good 8c41ccec839c622b2d1be769a95405e4e9a4cb20 > >> >> # first bad commit: [b5712bf89b4bbc5bcc9ebde8753ad222f1f68296] > >> >> # irqchip/gic-v3-its: Provide MSI parent for PCI/MSI[-X] > >> > > >> > There were follow up fixes on this, so isolating this one is not really > >> > conclusive. > >> > > >> > Is the problem still there on v6.16 and v6.17-rc1? > > > > Yeah, there are way too many things that have been addressed since. > > kdump is also a particularly nasty case, as it tends to rely on the > > redistributor tables programmed by the previous kernel. > > Thanks for providing a clue. This may also explain explain why I fails > to reproduce this issue against 1st kernel even with the same cmdline of > the kdump kernel. I'm not sure that's a clue. It's only an indication that things are not necessarily easy to spot. Has it ever been reproduced on bare metal? Have you tried v6.16 as instructed? > > > > > Also, this says "virtual machines". What's the hypervisor? > > I'll contact the lab administrator. What kinds of info I should collect > to help you narrow down the issue? Surely you know what hypervisor you're running on, right? > > > How hard is it to reproduce? > > It can be reproduced reliably on certain machines. But as of writing I > haven't reproduced it on other KVM virtual machines on three different > host machines. Which machines? I'm sorry, but if you want help on this, you'll have to provide actual information. Thanks, M. -- Without deviation from the norm, progress is not possible.