From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:52036) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fIy7G-0004NC-2W for qemu-devel@nongnu.org; Wed, 16 May 2018 11:13:22 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fIy7C-0001Kd-Ok for qemu-devel@nongnu.org; Wed, 16 May 2018 11:13:21 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:34636 helo=mx1.redhat.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1fIy7C-0001KT-K2 for qemu-devel@nongnu.org; Wed, 16 May 2018 11:13:18 -0400 Date: Wed, 16 May 2018 18:13:17 +0300 From: "Michael S. Tsirkin" Message-ID: <20180516180847-mutt-send-email-mst@kernel.org> References: <1523953455-28053-1-git-send-email-wanpengli@tencent.com> <20180417205913.GC29865@localhost.localdomain> <02887fa6-d7c8-bc39-6e65-3c3caec5b903@redhat.com> <20180419195610.GA29865@localhost.localdomain> <98f48c44-e55a-2bd2-0d41-5643f35bce68@redhat.com> <20180419215320.GC29865@localhost.localdomain> <20180512010007-mutt-send-email-mst@kernel.org> <20180516172121-mutt-send-email-mst@kernel.org> <2871c099-79fe-8432-12c9-637e743cc89c@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <2871c099-79fe-8432-12c9-637e743cc89c@redhat.com> Subject: Re: [Qemu-devel] [PATCH RESEND v2] i386/kvm: add support for KVM_CAP_X86_DISABLE_EXITS List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Paolo Bonzini Cc: Eduardo Habkost , Wanpeng Li , qemu-devel@nongnu.org, kvm@vger.kernel.org, Radim =?utf-8?B?S3LEjW3DocWZ?= On Wed, May 16, 2018 at 05:04:41PM +0200, Paolo Bonzini wrote: > On 16/05/2018 16:22, Michael S. Tsirkin wrote: > >> kvm-hint-dedicated=on only sets the CPUID bit, which Linux for example > >> uses that to disable pv spinlocks. "-realtime dedicated-cpus=on" only > >> disables the vmexits. You can use the two independently. > > > > But when would you want to use the two independently? > > 1) For testing > > 2) When some of your QEMUs are too old to support kvm-hint-dedicated=on, > you may still want to use -realtime dedicated-cpus=on to get better > performance on the new one. > > Paolo For the second purpose, can't we handle this using machine types? -- MST