From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-we0-x22c.google.com (mail-we0-x22c.google.com [IPv6:2a00:1450:400c:c03::22c]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id E3C521A0550 for ; Sat, 21 Feb 2015 01:13:03 +1100 (AEDT) Received: by wevk48 with SMTP id k48so5867711wev.3 for ; Fri, 20 Feb 2015 06:13:00 -0800 (PST) Sender: Paolo Bonzini Message-ID: <54E740E7.5090806@redhat.com> Date: Fri, 20 Feb 2015 15:12:55 +0100 From: Paolo Bonzini MIME-Version: 1.0 To: Alexander Graf , Bogdan Purcareata , linuxppc-dev@lists.ozlabs.org, linux-rt-users@vger.kernel.org, bigeasy@linutronix.de Subject: Re: [PATCH 0/2] powerpc/kvm: Enable running guests on RT Linux References: <1424251955-308-1-git-send-email-bogdan.purcareata@freescale.com> <54E73A6C.9080500@suse.de> In-Reply-To: <54E73A6C.9080500@suse.de> Content-Type: text/plain; charset=windows-1252 Cc: scottwood@freescale.com, mihai.caraman@freescale.com, Thomas Gleixner , linux-kernel@vger.kernel.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On 20/02/2015 14:45, Alexander Graf wrote: > > > On 18.02.15 10:32, Bogdan Purcareata wrote: >> This patchset enables running KVM SMP guests with external interrupts on an >> underlying RT-enabled Linux. Previous to this patch, a guest with in-kernel MPIC >> emulation could easily panic the kernel due to preemption when delivering IPIs >> and external interrupts, because of the openpic spinlock becoming a sleeping >> mutex on PREEMPT_RT_FULL Linux. >> >> 0001: converts the openpic spinlock to a raw spinlock, in order to circumvent >> this behavior. While this change is targeted for a RT enabled Linux, it has no >> effect on upstream kvm-ppc, so send it upstream for better future maintenance. >> >> 0002: introduces a limit on the maximum VCPUs a guest can have, in order to >> prevent potential DoS attack due to large system latencies. This patch is >> targeted to RT (due to CONFIG_PREEMPT_RT_FULL), but it can also be applied on >> upstream Linux, with no effect. Not sure if it's best to send it upstream and >> have a hanging CONFIG_PREEMPT_RT_FULL check there, with no effect, or send it >> against linux-stable-rt. Please apply as you consider appropriate. > > Thomas, what is the usual approach for patches like this? Do you take > them into your rt tree or should they get integrated to upstream? Patch 1 is definitely suitable for upstream, that's the reason why we have raw_spin_lock vs. raw_spin_unlock. Paolo