Re: [Xen-devel] Foreign VCPU register change?

[Keir Fraser <keir.xen@xxxxxxxxx>]

On 23/08/2012 18:25, "Cutter 409" <cutter409@xxxxxxxxx> wrote:

> With Xen-4.1.2:
> 
> I'm trying to change a register value in a paused vmx vcpu. The general
> process looks like this:
> 
> 1. Some vmexit calls vcpu_sleep_nosync(v) on the vcpu
> 2. From dom0, I issue a domctl to change a register via
> v->arch.guest_context.user_reg, then vcpu_wake(v)

Which domctl? From dom0 userspace you can use the libxc functions
xc_vcpu_getcontext() and xc_vcpu_setcontext() to read/modify register state.

You can read the libxc sources to see what hypercall these map to, if you
don't want to use libxc for any reason.

 -- Keir

> However, the guest register does not seem to be changed when I do it this way.
> Is there something I need to do to mark the registers as "dirty" ? Is there a
> way to force the foreign vcpu to update the changed registers? Or maybe I just
> have to change the registers somewhere else?
> 
> I've tried directly using vmcs_enter(v), __vmwrite(), vmcs_exit(v) also, but
> that doesn't seem to make a change either.
> 
> Thanks!
> 
> 
> 
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