From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx2.suse.de (cantor2.suse.de [195.135.220.15]) (using TLSv1 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3058D1A0550 for ; Sat, 21 Feb 2015 01:16:11 +1100 (AEDT) Message-ID: <54E741A6.8000308@suse.de> Date: Fri, 20 Feb 2015 15:16:06 +0100 From: Alexander Graf MIME-Version: 1.0 To: Paolo Bonzini , 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> <54E740E7.5090806@redhat.com> In-Reply-To: <54E740E7.5090806@redhat.com> 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 20.02.15 15:12, Paolo Bonzini wrote: > > > 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. I see, perfect :). Bogdan, please resend patch 1 with CC to kvm-ppc@vger so that I can pick it up from patchworks. Alex