From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ian Campbell Subject: Re: [hybrid]: unable to boot hvm due to eflags.ID Date: Fri, 4 May 2012 11:53:27 +0100 Message-ID: <1336128807.2361.56.camel@zakaz.uk.xensource.com> References: <20120503191025.7c2cec2e@mantra.us.oracle.com> <1336122502.2361.7.camel@zakaz.uk.xensource.com> <20120504104902.GA6127@ocelot.phlegethon.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20120504104902.GA6127@ocelot.phlegethon.org> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Tim Deegan Cc: "Xen-devel@lists.xensource.com" List-Id: xen-devel@lists.xenproject.org On Fri, 2012-05-04 at 11:49 +0100, Tim Deegan wrote: > At 10:08 +0100 on 04 May (1336126102), Ian Campbell wrote: > > What does the guest EFLAGS actually contain at this point? Is it > > different to what it contains on non-hybrid dom0? > > > > How do we execute 16 bit code in a VMX guest these days, using vm86 or > > by emulation? > > Both, and also sometimes neither. :) Of course ;-) > If the chip supports it, we just run in real mode inside the VM (this is > called "unrestricted guest" in the VMX code and will be reported in the > Xen boot messages). Thanks, I thought this had been added but didn't know the name of the feature. > Otherwise we run in vm86 when we can, and emulate things that vm86 > doesn't support, and all I/O. We also have to emulate when the segment > state is wierd (e.g., big-real-mode) because the VMENTER into vm86 has > stricter checks on segment state than actual real mode. > > > How does that interact with EFLAGS_ID I wonder (although > > why hybrid dom0 would have any bearing on this I've no idea). > > I'm not aware of anything deliberately tinkering with EFLAGS_ID, I couldn't find any use other than the definition, although it maybe open coded somewhere. > but > it's possible that vm86 interacts with it (of that we accidentally lose > some parts of EFLAGS in emulation). Yeah, but I can't figure out why hybrid dom0 would change that... Ian,