From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ian Campbell Subject: Re: hvm crash on hypercall event channel Date: Wed, 11 Apr 2012 13:06:29 +0100 Message-ID: <1334145989.16387.7.camel@zakaz.uk.xensource.com> References: <20120410121344.GA1955@ocelot.phlegethon.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Daniel Castro Cc: "g@phlegethon.org" , "Tim (Xen.org)" , "xen-devel@lists.xensource.com" List-Id: xen-devel@lists.xenproject.org On Wed, 2012-04-11 at 13:02 +0100, Daniel Castro wrote: > On Tue, Apr 10, 2012 at 9:13 PM, Tim Deegan wrote: > > At 20:30 +0900 on 10 Apr (1334089815), Daniel Castro wrote: > >> Hello All, > >> > >> I am writing the PV-Drivers for Seabios. > >> > >> When I put a request on the front ring and issue the hypercall to > >> notify, the hvm guest crashes. > >> > >> Here is the dmesg output: > >> > >> (XEN) realmode.c:116:d10 Failed to emulate insn. > >> (XEN) realmode.c:166:d10 Real-mode emulation failed @ f000:00001c4b: > >> 0f aa ba b2 00 ec > > > > 0F AA is RSM, which is a pretty surprising instruction to find in a > > hypercall invocation -- or indeed anywhere outside machine-specific SMM > > code. Is there SMM code in SeaBIOS? It may be that you've ended up > > jumping to a misaligned instruction boundary. > > > >> Nothing out of the ordinary. Except that the hypercall is issued under > >> 16bit, It works under 32bit. > > > > Are you using the hypercall page to make your hypercall? Its contents > > don't make sense in 16-bit mode, only in 32-bit and 64-bit. Since the > > register arguments are 32-bit anyway you might want to make all your > > hypercalls from 32-bit code anyway; otherwise you'll need to make your > > own 16-bit stubs, with the right prefixes for the MOV imm32. > > I have no idea how to fix this :( It's looking likely that you'll have to go to 32 bit mode to do all of the actual I/O associated with the PV devices. That ought to simplify a bunch of stuff WRT handling the rings etc too. Ian.