Re: [Qemu-devel] [PATCH V3 0/4] Add vPMU vPMU support under TCG mode

[Peter Maydell]

On 10 February 2017 at 15:00, Peter Maydell <address@hidden> wrote:
> On 7 February 2017 at 21:49, Wei Huang <address@hidden> wrote:
>> QEMU has implemented cycle count support for guest VM under TCG mode.
>> But this feature is not complete. In fact using perf inside a
>> 64-bit Linux guest VM (under TCG) can cause the following kernel panic
>> because some PMU registers are not implemented.
>>
>> [  329.445970] [<fffffe000009e600>] armv8pmu_enable_event+0x58/0x8c
>> [  329.446713] [<fffffe0000621e74>] armpmu_start+0x4c/0x74
>>
>> This patchset solves the problem by adding support for missing vPMU
>> registers. Basic perf test can work (both ACPI and DT) now under TCG
>> by applying this patchset.
>>
>> address@hidden ~]# perf stat ls
>>  Performance counter stats for 'ls':
>>
>>         226.740256      task-clock (msec)         #    0.312 CPUs utilized
>>                 76      context-switches          #    0.335 K/sec
>>                  0      cpu-migrations            #    0.000 K/sec
>>                 64      page-faults               #    0.282 K/sec
>>        186,031,410      cycles                    #    0.820 GHz      
>> (36.40%)
>>    <not supported>      stalled-cycles-frontend
>>    <not supported>      stalled-cycles-backend
>>      <not counted>      instructions               (0.00%)
>>    <not supported>      branches
>>      <not counted>      branch-misses              (0.00%)
>>
>> V2->V3:
>>  * Remove PMXEVCNTR_EL0 support
>>  * Add read access support for PMXEVTYPER and change the CONSTRAINED
>>    UNPREDICTABLE behavior of PMXEVTYPER to RAZ/WI.
>>
>> V1->V2:
>>   * Change most PMU registers to 64bit and the behavior of PMXEVTYPER
>>   * Add support for PMXEVCNTR_EL0
>>   * Misc fixes (DT, ID_AA64DFR0_EL1, ...) under TCG mod
>
> Applied to target-arm.next, thanks.

...though patch 1 breaks compilation of linux-user targets. I've
fixed it up by moving the #ifndef CONFIG_USER_ONLY to the right
place to cover the new regdefs.

thanks
-- PMM