From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Zijlstra Subject: Re: [PATCH v2 2/4] powerpc/spinlock: support vcpu preempted check Date: Wed, 6 Jul 2016 09:58:14 +0200 Message-ID: <20160706075814.GF30921@twins.programming.kicks-ass.net> References: <1467124991-13164-1-git-send-email-xinhui.pan@linux.vnet.ibm.com> <1467124991-13164-3-git-send-email-xinhui.pan@linux.vnet.ibm.com> <577C8FE3.3010208@linux.vnet.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: linux-s390 , Davidlohr Bueso , benh@kernel.crashing.org, kvm , xinhui , boqun.feng@gmail.com, will.deacon@arm.com, "linux-kernel@vger.kernel.org" , Waiman Long , virtualization@lists.linux-foundation.org, Ingo Molnar , Paul Mackerras , mpe@ellerman.id.au, schwidefsky@de.ibm.com, Paolo Bonzini , Paul McKenney , linuxppc-dev@lists.ozlabs.org To: Wanpeng Li Return-path: Content-Disposition: inline In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org List-Id: kvm.vger.kernel.org On Wed, Jul 06, 2016 at 02:46:34PM +0800, Wanpeng Li wrote: > > SO it's easy for ppc to implement such interface. Note that yield_count is > > set by powerVM/KVM. > > and only pSeries can run a guest for now. :) > > > > I also review x86 related code, looks like we need add one hyer-call to get > > such vcpu preemption info? > > There is no such stuff to record lock holder in x86 kvm, maybe we > don't need to depend on PLE handler algorithm to guess it if we can > know lock holder vCPU directly. x86/kvm has vcpu->preempted to indicate if a vcpu is currently preempted or not. I'm just not sure if that is visible to the guest or how to make it so.