Dump VMCS on Intel CPU

Dump VMCS on Intel CPU

[Mukesh Rathor]

Hi,

I'd like to dump VMCS for all HVM VCPUs from a cpu that is running kdb. While 
this CPU is doing kdb commands, all other CPUs are spinning disabled in kdb 
function.

On AMD, it was simple by calling svm_dump_vmcb() by passing vmcb from
each vcpu struct. Looking at vmcs.c, I see quite a bit of mumbo-jumbo in
terms of setting context, even IPI other CPUs, etc. That doesn't work
for me. So the question is, is there any reason followig won't work?

   for each hvm vcpu {
       __vmptrld(virt_to_maddr(vp->arch.hvm_vmx.vmcs));
       vmcs_dump_vcpu();
   }
   if ( is_hvm_vcpu(current) )
       __vmptrld(virt_to_maddr(current->arch.hvm_vmx.vmcs));


Seems to work ok, but I want to make sure.

thanks,
Mukesh

Re: Dump VMCS on Intel CPU

[Keir Fraser]

On 06/06/2009 04:06, "Mukesh Rathor" <mukesh.rathor@oracle.com> wrote:

> On AMD, it was simple by calling svm_dump_vmcb() by passing vmcb from
> each vcpu struct. Looking at vmcs.c, I see quite a bit of mumbo-jumbo in
> terms of setting context, even IPI other CPUs, etc. That doesn't work
> for me. So the question is, is there any reason followig won't work?
> 
>    for each hvm vcpu {
>        __vmptrld(virt_to_maddr(vp->arch.hvm_vmx.vmcs));
>        vmcs_dump_vcpu();
>    }
>    if ( is_hvm_vcpu(current) )
>        __vmptrld(virt_to_maddr(current->arch.hvm_vmx.vmcs));
> 
> 
> Seems to work ok, but I want to make sure.

Intel say you should VMCLEAR on the last CPU to VMPTRLD the VMCS. For us
that means if v->arch.hvm_vmx.active_cpu != smp_processor_id() nor -1.
However VMPTRLD is not described as failing if this is not carried out. So,
I guess you may get away with it. If you want to be super safe you might
VMCLEAR on CPUs as they rendezvous with kdb.

 -- Keir