From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paolo Bonzini Subject: Re: [PATCH 0/2] powerpc/kvm: Enable running guests on RT Linux Date: Fri, 20 Feb 2015 15:12:55 +0100 Message-ID: <54E740E7.5090806@redhat.com> References: <1424251955-308-1-git-send-email-bogdan.purcareata@freescale.com> <54E73A6C.9080500@suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Cc: linux-kernel@vger.kernel.org, scottwood@freescale.com, mihai.caraman@freescale.com, Thomas Gleixner To: Alexander Graf , Bogdan Purcareata , linuxppc-dev@lists.ozlabs.org, linux-rt-users@vger.kernel.org, bigeasy@linutronix.de Return-path: In-Reply-To: <54E73A6C.9080500@suse.de> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-rt-users.vger.kernel.org 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