Re: [Xen-devel] [PATCH] x86/vm_event: correctly gather gs_shadow value

[Tamas K Lengyel <tamas@xxxxxxxxxxxxx>]

On Wed, May 1, 2019 at 8:20 AM Razvan Cojocaru
<rcojocaru@xxxxxxxxxxxxxxx> wrote:
>
> On 5/1/19 4:58 PM, Tamas K Lengyel wrote:
> >>> It might be worth introducing a "sync state from hw" hook which collects
> >>> all the data we intend to pass to the introspection agent.
> >>
> >> You mean adding another hvm hook?
> >
> > Actually, instead of another hook I think what would make sense it to
> > just update vmx_save_vmcs_ctxt to automatically refresh the cached
> > register values when it's called with "v == current". Thoughts?
>
> That's probably the better way to go about it, since otherwise the
> xc_hvm_getcontext_partial() hypercall will suffer from the same problem.
> (there are two ways of getting guest state: one is via the vm_event
> cached values, the other is via the aforementioned hypercall).

True, although issuing the hypercall in the vm_event callback is
actually fine - that's how I found the issue to begin with, since the
vCPU will be scheduled out with the cached registers refreshed and
thus be different then what the vm_event itself had. But other callers
of the hypercall can run into the problem if the guest/vcpu is not
paused.

Tamas

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxxx
https://lists.xenproject.org/mailman/listinfo/xen-devel