Re: [Xen-devel] RIP register value in p2m_mem_access_check()

[Tim Deegan <tim@xxxxxxx>]

At 14:33 +0000 on 06 Mar (1362580383), Jan Beulich wrote:
> >>> On 06.03.13 at 14:49, Razvan Cojocaru <rzvncj@xxxxxxxxx> wrote:
> >>  That wouldn't match your observation (the two values were
> >> much farther apart), unless a call or jump got emulated.
> >>
> >> Further, after emulation, the user_regs.eip value should be the
> >> canonical one.
> > 
> > Well, I've downloaded and installed a fresh copy of Xen 4.2.0 from the 
> > official website, and added the printk() to p2m.c (the only modification 
> > I've done):
> > 
> > 1311         req->vcpu_id = v->vcpu_id;
> > 1312
> > 1313         printk("v->arch.user_regs.eip: 0x%016lx, 
> > __vmread(GUEST_RIP):0x%016lx\n",
> > 1314                v->arch.user_regs.eip, __vmread(GUEST_RIP));
> > 1315     }
> 
> I know close to nothing about the paths that can lead here, and
> hence I can't assess whether expecting consistency at this point
> is valid. All I can tell is that right after VM exit (i.e. at the top of
> vmx_vmexit_handler()) the two values ought to be consistent.

I don't think so -- v->arch.user_regs is only brought up to date during
context switches.  For the currently running vcpu you should be looking
at guest_cpu_user_regs().

Cheers,

Tim.

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