From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marcelo Tosatti Subject: Re: [PATCH v3 00/15] KVM: MMU: fast zap all shadow pages Date: Mon, 22 Apr 2013 20:02:34 -0300 Message-ID: <20130422230233.GA3337@amt.cnet> References: <1366093973-2617-1-git-send-email-xiaoguangrong@linux.vnet.ibm.com> <20130421130346.GE8997@redhat.com> <20130421152751.GB28437@amt.cnet> <20130421153508.GA28842@amt.cnet> <20130422123938.GB10970@redhat.com> <20130422224553.b4dd57075cc7e32aacaadc01@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Gleb Natapov , Xiao Guangrong , avi.kivity@gmail.com, linux-kernel@vger.kernel.org, kvm@vger.kernel.org To: Takuya Yoshikawa Return-path: Content-Disposition: inline In-Reply-To: <20130422224553.b4dd57075cc7e32aacaadc01@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On Mon, Apr 22, 2013 at 10:45:53PM +0900, Takuya Yoshikawa wrote: > On Mon, 22 Apr 2013 15:39:38 +0300 > Gleb Natapov wrote: > > > > > Do not want kvm_set_memory (cases: DELETE/MOVE/CREATES) to be > > > > suspectible to: > > > > > > > > vcpu 1 | kvm_set_memory > > > > create shadow page > > > > nuke shadow page > > > > create shadow page > > > > nuke shadow page > > > > > > > > Which is guest triggerable behavior with spinlock preemption algorithm. > > > > > > Not only guest triggerable as in the sense of a malicious guest, > > > but condition above can be induced by host workload with non-malicious > > > guest system. > > > > > Is the problem that newly created shadow pages are immediately zapped? > > Shouldn't generation number/kvm_mmu_zap_all_invalid() idea described here > > https://lkml.org/lkml/2013/4/22/111 solve this? > > I guess so. That's what Avi described when he tried to achieve > lockless TLB flushes. Mixing that idea with Xiao's approach will > achieve reasonably nice performance, I think. Yes. > Various improvements should be added later on top of that if needed. > > > > Also kvm_set_memory being relatively fast with huge memory guests > > > is nice (which is what Xiaos idea allows). > > I agree with this point. But if so, it should be actually measured on > such guests, even if the algorithm looks promising. Works for me.