How to monitoring segment registers?

How to monitoring segment registers?

[Jun Koi]

Hi,

I am doing some profiling for a guest VM on KVM. One of things I want
to do is to monitor the activities of SS register.

Specifically, I want to be notified whenever guest's SS changes its
value (like when OS switches from userspace stack to kernel stack).

I imagine that I need to reprogram VMCS, so I can get VMEXIT anytime
SS changes its value.
Is that feasible? If so, which code should I look at in kvm code?

Many thanks,
Jun

Re: How to monitoring segment registers?

[Avi Kivity]

On 11/11/2009 06:19 PM, Jun Koi wrote:
> Hi,
>
> I am doing some profiling for a guest VM on KVM. One of things I want
> to do is to monitor the activities of SS register.
>
> Specifically, I want to be notified whenever guest's SS changes its
> value (like when OS switches from userspace stack to kernel stack).
>
> I imagine that I need to reprogram VMCS, so I can get VMEXIT anytime
> SS changes its value.
> Is that feasible? If so, which code should I look at in kvm code?
>    

Virtualization extensions don't allow trapping on segment register 
changes.  I recommend modifying qemu/tcg instead.

-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.