From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Hildenbrand Subject: Re: [PATCH] kvm: VMX: do not use vm-exit instruction length for fast MMIO Date: Fri, 18 Aug 2017 14:41:52 +0200 Message-ID: <3f6fd875-037c-91c8-b570-d5010751d175@redhat.com> References: <1502890494-35208-1-git-send-email-pbonzini@redhat.com> <901d4c2e-aa94-2002-babc-7f042946a327@redhat.com> <3b7afdfc-d308-7645-2105-6bb339188aa6@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Cc: rkrcmar@redhat.com, "Michael S. Tsirkin" , stable@vger.kernel.org To: Paolo Bonzini , linux-kernel@vger.kernel.org, kvm@vger.kernel.org Return-path: In-Reply-To: <3b7afdfc-d308-7645-2105-6bb339188aa6@redhat.com> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On 18.08.2017 14:35, Paolo Bonzini wrote: > On 18/08/2017 13:57, David Hildenbrand wrote: >> What about a hack: >> >> 1. clear instruction length when entering >> 2. check if instruction length is set when trying to forward the RIP >> 2a. if set, use it >> 2b. if not set, compute it > > It's undefined, so we don't know that the instruction length remains > zero (also, on older processors and possibly some nested setups the > field is read-only). Oh I see, too bad :( > > Testing the hypervisor bit is the first line of action. > > Paolo -- Thanks, David