[Qemu-devel] Memory Tracking API

[Qemu-devel] Memory Tracking API

[Jaspal]

Hi ,

Is it possible to keep a count of reads / writes taking place in a vm 
using qemu ( using kvm as hypervisor ) ? Is there a api ( or any patch ) 
for it ?

Thanks ,
Jaspal

Re: [Qemu-devel] Memory Tracking API

[Richard W.M. Jones]

On Thu, May 17, 2012 at 11:36:24PM +0530, Jaspal wrote:
> Hi ,
> 
> Is it possible to keep a count of reads / writes taking place in a
> vm using qemu ( using kvm as hypervisor ) ? Is there a api ( or any
> patch ) for it ?

Memory reads and writes is surely going to generate a huge
amount of output!

There are various DEBUG_* symbols at the top of exec.c and ioport.c.
I've only used a few of these:

  DEBUG_UNASSIGNED - prints a message when an unmapped page is
      referenced (TCG only, presumably?)

  DEBUG_IOPORT - prints a message when any I/O port is referenced

  DEBUG_UNUSED_IOPORT - prints a message when a non-emulated I/O port
      is referenced

There are several more if you look at the code.

Rich.

-- 
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Re: [Qemu-devel] Memory Tracking API

[Jaspal]

On 05/18/2012 12:17 AM, Richard W.M. Jones wrote:
> On Thu, May 17, 2012 at 11:36:24PM +0530, Jaspal wrote:
>> Hi ,
>>
>> Is it possible to keep a count of reads / writes taking place in a
>> vm using qemu ( using kvm as hypervisor ) ? Is there a api ( or any
>> patch ) for it ?
> Memory reads and writes is surely going to generate a huge
> amount of output!
>
> There are various DEBUG_* symbols at the top of exec.c and ioport.c.
> I've only used a few of these:
>
>    DEBUG_UNASSIGNED - prints a message when an unmapped page is
>        referenced (TCG only, presumably?)
>
>    DEBUG_IOPORT - prints a message when any I/O port is referenced
>
>    DEBUG_UNUSED_IOPORT - prints a message when a non-emulated I/O port
>        is referenced
>
> There are several more if you look at the code.
>
> Rich.
>

When are these functions called : kvm_read_guest_page , 
kvm_read_guest_atomic , kvm_write_guest_page present in kvm_main.c  ? 
When qemu wants to read/write to a page ? If qemu has to read/write on 
the vm's memory ( RAM ) , does the process always involve kvm ?

Thanks ,
Jaspal