From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paolo Bonzini Subject: Re: [PATCH 5/5] KVM: x86: Using TSC deadline may cause multiple interrupts by user writes Date: Wed, 08 Oct 2014 12:07:47 +0200 Message-ID: <54350CF3.80403@redhat.com> References: <1412287806-16016-1-git-send-email-namit@cs.technion.ac.il> <1412287806-16016-6-git-send-email-namit@cs.technion.ac.il> <20141006205737.GC2722@potion.brq.redhat.com> <4E3FA8A7-6CEF-4077-AD91-9AAE1AF86FEF@gmail.com> <20141008100619.GA20422@potion.brq.redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: Nadav Amit , joro@8bytes.org, kvm@vger.kernel.org To: =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= , Nadav Amit Return-path: Received: from mx1.redhat.com ([209.132.183.28]:32493 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754434AbaJHKIB (ORCPT ); Wed, 8 Oct 2014 06:08:01 -0400 In-Reply-To: <20141008100619.GA20422@potion.brq.redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: Il 08/10/2014 12:06, Radim Kr=C4=8Dm=C3=A1=C5=99 ha scritto: > > > - why is host_initiated required? >=20 > > Since if the guest writes to the MSR, it means it wants to rearm th= e TSC deadline. Even if the deadline passed, interrupt should be trigge= red. >=20 > MSR isn't 0, so the deadline hasn't passed for the guest yet. >=20 > > If the guest writes the same value on the deadline MSR twice, it mi= ght expect two interrupts. >=20 > When guest writes to it without getting an interrupt first, it might > expect just one. (Which it better IMO.) Indeed that was my doubt as well. Paolo