From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from AM1EHSOBE005.bigfish.com (am1ehsobe005.messaging.microsoft.com [213.199.154.208]) (using TLSv1 with cipher AES128-SHA (128/128 bits)) (Client CN "mail.global.frontbridge.com", Issuer "Microsoft Secure Server Authority" (not verified)) by ozlabs.org (Postfix) with ESMTPS id 0989E1007D4 for ; Sat, 3 Mar 2012 04:17:32 +1100 (EST) Message-ID: <4F5100A0.8040802@freescale.com> Date: Fri, 2 Mar 2012 11:17:20 -0600 From: Scott Wood MIME-Version: 1.0 To: Alexander Graf Subject: Re: [PATCH] PPC: Don't sync timebase when inside VM References: <1330697553-27156-1-git-send-email-agraf@suse.de> <20120302162058.GA24552@schlenkerla.am.freescale.net> <9A229F04-DFC9-485D-AB06-B1A4F0AEB348@suse.de> In-Reply-To: <9A229F04-DFC9-485D-AB06-B1A4F0AEB348@suse.de> Content-Type: text/plain; charset="ISO-8859-1" Cc: linuxppc-dev , kvm list , "" , msm@freescale.com List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On 03/02/2012 10:30 AM, Alexander Graf wrote: > > On 02.03.2012, at 17:20, Scott Wood wrote: > >> On Fri, Mar 02, 2012 at 03:12:33PM +0100, Alexander Graf wrote: >>> When running inside a virtual machine, we can not modify timebase, so >>> let's just not call the functions for it then. >>> >>> This resolves hangs when booting e500 SMP guests on overcommitted hosts. >>> >>> Reported-by: Stuart Yoder >>> Signed-off-by: Alexander Graf >>> --- >>> arch/powerpc/platforms/85xx/smp.c | 7 +++++++ >>> 1 files changed, 7 insertions(+), 0 deletions(-) >>> >>> diff --git a/arch/powerpc/platforms/85xx/smp.c b/arch/powerpc/platforms/85xx/smp.c >>> index ff42490..d4b6c1f 100644 >>> --- a/arch/powerpc/platforms/85xx/smp.c >>> +++ b/arch/powerpc/platforms/85xx/smp.c >>> @@ -249,6 +249,13 @@ void __init mpc85xx_smp_init(void) >>> smp_85xx_ops.cause_ipi = doorbell_cause_ipi; >>> } >>> >>> + /* When running under a hypervisor, we can not modify tb */ >>> + np = of_find_node_by_path("/hypervisor"); >>> + if (np) { >>> + smp_85xx_ops.give_timebase = NULL; >>> + smp_85xx_ops.take_timebase = NULL; >>> + } >>> + >>> smp_ops = &smp_85xx_ops; >> >> Again, for 85xx we should *never* sync the timebase in the kernel, >> hypervisor or no. > > The code says "if the kexec config option is enabled, do the sync". I'm fairly sure it's there for a reason. Sigh. I forgot about that. It's because instead of doing kexec the simple way, we actually physically reset the core. We really shouldn't do that. And we *really* shouldn't do it just because CONFIG_KEXEC is defined, regardless of whether we're actually booting from kexec. -Scott