From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tim Deegan Subject: Re: hvm crash on hypercall event channel Date: Tue, 10 Apr 2012 13:13:44 +0100 Message-ID: <20120410121344.GA1955@ocelot.phlegethon.org> References: Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline 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 , g@phlegethon.org Cc: xen-devel@lists.xensource.com List-Id: xen-devel@lists.xenproject.org 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. Cheers, Tim.