From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ingo Molnar Subject: Re: %fs PDA & KVM Date: Sun, 11 Mar 2007 13:41:46 +0100 Message-ID: <20070311124146.GA15115@elte.hu> References: <20070311122441.GA10774@elte.hu> <45F3F85D.7000509@qumranet.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: kvm-devel To: Avi Kivity Return-path: Content-Disposition: inline In-Reply-To: <45F3F85D.7000509-atKUWr5tajBWk0Htik3J/w@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org Errors-To: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org List-Id: kvm.vger.kernel.org * Avi Kivity wrote: > >i'm also wondering about this bit: > > > > kvm_run->exit_type = 0; > > if (fail) { > > kvm_run->exit_type = KVM_EXIT_TYPE_FAIL_ENTRY; > > kvm_run->exit_reason = vmcs_read32(VM_INSTRUCTION_ERROR); > > kvm_cr3_cache_sync(vcpu); > > r = 0; > > } else { > > if (fs_gs_ldt_reload_needed) { > > load_ldt(ldt_sel); > > load_fs(fs_sel); > > > >are you sure we dont need an FS reload in the 'fail' case? > > > > The manual is not explicit about it, but I think that an entry failure > during loading of guest state _can_ cause fs to be loaded, so yes, > that path is missing the segment reloads. ok, i'll send a patch. > Non -rt kvm cannot preempt there even with CONFIG_PREEMPT=y. Can > interrupts reference current? If so, that fix is needed badly for > .21. interrupts can reference 'current' (although it's generally not encouraged) - for example scheduler_tick(), but the IRQ entry code loads %fs anyway via SAVE_ALL, so it's not an issue. Ingo ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys-and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV