From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from gate.crashing.org (gate.crashing.org [63.228.1.57]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 8697C1A07F1 for ; Sat, 17 Oct 2015 13:01:25 +1100 (AEDT) Message-ID: <1445047273.24309.35.camel@kernel.crashing.org> Subject: Re: [PATCH] powerpc: on crash, kexec'ed kernel needs all CPUs are online From: Benjamin Herrenschmidt To: Laurent Vivier , Michael Ellerman Cc: Paul Mackerras , linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, dgibson@redhat.com, thuth@redhat.com Date: Sat, 17 Oct 2015 07:31:13 +0530 In-Reply-To: <5620ABC5.6060300@redhat.com> References: <1444935658-27319-1-git-send-email-lvivier@redhat.com> <1444961690.28419.1.camel@ellerman.id.au> <5620ABC5.6060300@redhat.com> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Fri, 2015-10-16 at 09:48 +0200, Laurent Vivier wrote: > > Yes, we know :) > > On the crash, as the CPUs are offline, kernel doesn't call > opal_return_cpu(), so for OPAL all these CPU are always in the > kernel. Hrm and they may even be in winkle state, so basically off... waking them up *could* be a tricky business. I suppose we could, near the last stage of kexec, patch the 0x100 vector to send anybody coming in to a kexec wait loop, and then machine gun the IPIs. But that will make them come in with an unclean ICP needing an EOI, I'm not sure we handle that very well. Ideally we could just soft-reset them but that's broken on P8. Cheers, Ben.