From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeremy Fitzhardinge Subject: Re: [RFC PATCH v1 3/5] KVM: Add paravirt kvm_flush_tlb_others Date: Tue, 01 May 2012 15:49:50 -0700 Message-ID: <4FA0688E.8030200@goop.org> References: <20120427161727.27082.43096.stgit@abhimanyu> <20120427162401.27082.59387.stgit@abhimanyu> <4F9D32B4.8040002@redhat.com> <1335865176.13683.120.camel@twins> <4F9FBF38.2060903@redhat.com> <1335869827.13683.133.camel@twins> <1335869998.13683.135.camel@twins> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: Avi Kivity , "Nikunj A. Dadhania" , mingo@elte.hu, mtosatti@redhat.com, kvm@vger.kernel.org, x86@kernel.org, vatsa@linux.vnet.ibm.com, linux-kernel@vger.kernel.org, hpa@zytor.com, Konrad Rzeszutek Wilk , Stefano Stabellini To: Peter Zijlstra Return-path: In-Reply-To: <1335869998.13683.135.camel@twins> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On 05/01/2012 03:59 AM, Peter Zijlstra wrote: > On Tue, 2012-05-01 at 12:57 +0200, Peter Zijlstra wrote: >> Anyway, I don't have any idea about the costs involved with >> HAVE_RCU_TABLE_FREE, but I don't think its much.. otherwise these other >> platforms (PPC,SPARC) wouldn't have used it, gup_fast() is a very >> specific case, whereas mmu-gather is something affecting pretty much all >> tasks. > Which reminds me, I thought Xen needed this too, but a git grep on > HAVE_RCU_TABLE_FREE shows its still only ppc and sparc. > > Jeremy? Yeah, I was thinking that too, but I can't remember what we did to resolve it. For pure PV guests, gupf simply isn't used, so the problem is moot. But for dom0 or PCI-passthrough it could be. Konrad, Stefano? J