On 4/3/19 7:57 AM, Diego Alejandro Parra Guzman wrote:
Hello Julien Grall
Hi Diego,
thank you for your replied, you have clarified many of my doubts.
I have been implementing some basic functionality for the PMU :
Here small description:
* getpmuinfo_attr : /* @brief get PMU
info, including number of Counters, and control counters */
* enable_all_pmu_counters: /* @brief Enable the cycle
counter register PMCCNTR_EL0, and any implemented event counter
PMEVCNTR<n>_EL0 */
* disable_all_pmu_counters /* @brief Disable the cycle counter
register PMCCNTR_EL0, and any implemented event counter
PMEVCNTR<n>_EL0. */
* reset_all_pmu_counters /* @brief Reset the cycle
counter register PMCCNTR_EL0, and any implemented event counter
PMEVCNTR<n>_EL0.*/
* enable_user_pmu_access /* @brief Enable user-mode
access to counters.*/
I think these can be used as primitives for XEN:
Now I have some additional questions about XEN:
* how can I include that primitives as a driver for ARM64 in XEN?
The inclusion in Xen will depend on your use cases. In my previous
e-mail, I described 2 uses cases:
1) A guest profiling itself
2) The hypervisor profiling the system (i.e guests and itself)
Which one are you implementing?
I've noticed that in linux kernel 4.14 - 4.15 $SOURCE/drivers/perf :
* there is and implementation for arm_pmu which is far better than
what I've implemented, is it hard to import that driver to XEN ?
arm_pmu is based on the Linux Perf subsystem. So I don't think you can
re-used the driver directly. Although, you could re-use some parts at
your convenience.
* again how can I include that primitives as a driver for ARM64 in XEN?
The first step is to define your use case. Then we can discuss how we
can implement PMU support in Xen.
* PMU is implemented for each CPU so how to deal with that?
It depends on what you are trying to achieve. If you are exposing the
PMU to the guest, then it is probably sufficient to store the context in
the guest vCPU state.
If you need to hold state in Xen as well, then you can use a per-cpu
storage (see include/xen/percpu.h).
Cheers,
--
Julien Grall
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel
