From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from gate.crashing.org (gate.crashing.org [63.228.1.57]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id DC3AF1A013F for ; Tue, 17 Jun 2014 19:32:31 +1000 (EST) Message-ID: <1402997541.7661.128.camel@pasglop> Subject: Re: [PATCH] powerpc/kvm: support to handle sw breakpoint From: Benjamin Herrenschmidt To: Alexander Graf Date: Tue, 17 Jun 2014 19:32:21 +1000 In-Reply-To: <53A0096D.3020108@suse.de> References: <1402780097-28827-1-git-send-email-maddy@linux.vnet.ibm.com> <53A0022D.5020108@suse.de> <1402996939.7661.126.camel@pasglop> <53A0096D.3020108@suse.de> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Cc: linuxppc-dev@lists.ozlabs.org, Madhavan Srinivasan , paulus@samba.org, kvm-ppc@vger.kernel.org, kvm@vger.kernel.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Tue, 2014-06-17 at 11:25 +0200, Alexander Graf wrote: > On 17.06.14 11:22, Benjamin Herrenschmidt wrote: > > On Tue, 2014-06-17 at 10:54 +0200, Alexander Graf wrote: > >> Also, why don't we use twi always or something else that actually is > >> defined as illegal instruction? I would like to see this shared with > >> book3s_32 PR. > > twi will be directed to the guest on HV no ? We want a real illegal > > because those go to the host (for potential emulation by the HV). > > Ah, good point. I guess we need different one for PR and HV then to > ensure compatibility with older ISAs on PR. Well, we also need to be careful with what happens if a PR guest puts that instruction in, do that stop its HV guest/host ? What if it's done in userspace ? Do that stop the kernel ? :-) Maddy, I haven't checked, does your patch ensure that we only ever stop if the instruction is at a recorded bkpt address ? It still means that a userspace process can practically DOS its kernel by issuing a lot of these causing a crapload of exits. Cheers, Ben. > Alex > > > I'm > > trying to see if I can get the architect to set one in stone in a future > > proof way. > > > > Cheers, > > Ben. > > > > -- > 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