RE: [Xen-devel] [PATCH] Calculate correct instruction length for data-fault VM exits on VT-x systems

["Petersson, Mats" <Mats.Petersson@xxxxxxx>]

> -----Original Message-----
> From: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx 
> [mailto:xen-devel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of 
> Keir Fraser
> Sent: 28 April 2006 10:15
> To: Petersson, Mats
> Cc: Khoa Huynh; xen-devel
> Subject: Re: [Xen-devel] [PATCH] Calculate correct 
> instruction length for data-fault VM exits on VT-x systems
> 
> 
> On 28 Apr 2006, at 10:02, Petersson, Mats wrote:
> 
> > I'll look at your previous suggestion of merging the MMIO emulation 
> > into x86_emulate later on today. We probably do need to sum up the 
> > length and pass it back to the caller - as that code 
> doesn't know how 
> > to update the correct field of the different processor 
> architectures 
> > (vmcb vs. vmcs vs. stack-frame for Para-virtual machine). But it 
> > shouldn't be particularly hard to achieve this.
> 
> The emulator uses and updates the eip field of the passed-in 
> regs structure. We may want to change this interface in 
> future by having the caller explicitly pass in a buffer 
> containing the instruction, and the number of valid bytes in 
> the buffer.  Or add a 'fetch_insn_byte' 
> callback hook to the emulator interface.

I think passing a buffer is the best choice here. And I suppose we can
always stuff vmc[bs]->rip into regs->eip and pull it back out again when
we get back - using a wrapper function may be the easiest way to achieve
this (at least short term). 

We will of course also need to get the communication with QEMU done in
some way.

I haven't spent any time looking at it so far... 

--
Mats
> 
>   -- Keir
> 
> 
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