From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:59884) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZkZ79-0000lX-MQ for qemu-devel@nongnu.org; Fri, 09 Oct 2015 10:57:47 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZkZ74-0001tt-NT for qemu-devel@nongnu.org; Fri, 09 Oct 2015 10:57:43 -0400 Received: from mx1.redhat.com ([209.132.183.28]:57246) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZkZ74-0001tn-Iq for qemu-devel@nongnu.org; Fri, 09 Oct 2015 10:57:38 -0400 References: <1444397988-20167-1-git-send-email-den@openvz.org> <1444397988-20167-3-git-send-email-den@openvz.org> <5617D20B.1080402@redhat.com> <20151009145358.GT27239@rkaganb.sw.ru> From: Paolo Bonzini Message-ID: <5617D5DD.7050701@redhat.com> Date: Fri, 9 Oct 2015 16:57:33 +0200 MIME-Version: 1.0 In-Reply-To: <20151009145358.GT27239@rkaganb.sw.ru> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH 2/2] kvm/x86: Hyper-V kvm exit List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Roman Kagan , "Denis V. Lunev" , virtualization@lists.linux-foundation.org, qemu-devel@nongnu.org, Andrey Smetanin , Vitaly Kuznetsov , "K. Y. Srinivasan" , Gleb Natapov On 09/10/2015 16:53, Roman Kagan wrote: >> > Why is this exit necessary? > The guest writes to synic-related MSRs and that should take "immediate" > effect. > > E.g. it may decide to disable or relocate the message page by writing to > SIMP MSR. The host is then supposed to stop accessing the old message > page before the vCPU proceeds to the next instruction. Hence the exit, > to allow the userspace to react accordingly before reentering the guest. Ok, thanks! Paolo