From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paolo Bonzini Subject: Re: [PATCH v1 4/5] kvm/x86: Hyper-V VMBus hypercall userspace exit Date: Wed, 20 Jan 2016 22:05:51 +0100 Message-ID: <569FF6AF.5010302@redhat.com> References: <1452595842-20880-1-git-send-email-asmetanin@virtuozzo.com> <1452595842-20880-5-git-send-email-asmetanin@virtuozzo.com> <009401d14ea5$dc8cf250$95a6d6f0$@samsung.com> <569F92AC.4030506@redhat.com> <20160120152034.GA3947@rkaganb.sw.ru> <569FBDA1.7010704@redhat.com> <20160120173106.GJ26969@rkaganb.sw.ru> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit To: 'Roman Kagan' , Pavel Fedin , 'Andrey Smetanin' , kvm@vger.kernel.org, 'Gleb Natapov' , 'Joerg Roedel' , "'K. Y. Srinivasan'" , 'Haiyang Zhang' , "'Denis V. Lunev'" , qemu-devel@nongnu.org Return-path: Received: from mail-wm0-f68.google.com ([74.125.82.68]:33818 "EHLO mail-wm0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754068AbcATVF4 (ORCPT ); Wed, 20 Jan 2016 16:05:56 -0500 Received: by mail-wm0-f68.google.com with SMTP id b14so6691185wmb.1 for ; Wed, 20 Jan 2016 13:05:55 -0800 (PST) In-Reply-To: <20160120173106.GJ26969@rkaganb.sw.ru> Sender: kvm-owner@vger.kernel.org List-ID: On 20/01/2016 18:31, 'Roman Kagan' wrote: > On Wed, Jan 20, 2016 at 06:02:25PM +0100, Paolo Bonzini wrote: >> >> >> On 20/01/2016 16:20, 'Roman Kagan' wrote: >>>>> So we should not add a new exit >>> Why? VCPU exit codes are not a scarse resource. >> >> Indeed, but grouping makes things easier to understand. >> >>> So far we've envisaged two reasons for VCPU exit related to hyper-v: one >>> for hyper-v MSRs and the other for hypercalls. Since there was a >>> discussion on implementing generic MSR access by Peter we thought it >>> wiser to introduce a new VCPU exit for hyper-v hypercalls to avoid >>> interfering with the MSR implementation. >> >> That's a good idea. However, I think I'm not going to accept the MSR >> exit feature, and then the current Hyper-V exit API makes some sense >> indeed (it's just 3 values, transferring them all at once is not >> expensive at all). > > OK can we please sum up (as I'm now a bit confused) what we do now: > > 1) use a single vcpu exit for both Hyper-V cases (which implies we need > to fix this patchset to add the subcode for hypercalls) This. Paolo > or > > 2) use individual vcpu exits for Hyper-V MSRs and for Hyper-V hypercalls > (which implies we need to submit an incremental patch dropping the > subcode from Hyper-V MSR exit and renaming it to better describe the > reality)? > > Thanks, > Roman. > -- > To unsubscribe from this list: send the line "unsubscribe kvm" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html >