Re: [Qemu-arm] [PATCH RFC 1/1] arm64: add an option to turn on/off vpmu support

[Peter Maydell]

On 29 July 2016 at 16:08, Wei Huang <address@hidden> wrote:
>
>
> On 07/29/2016 02:57 AM, Peter Maydell wrote:
>> On 28 July 2016 at 17:38, Wei Huang <address@hidden> wrote:
>>> This patch adds a pmu=[on/off] option to enable/disable vpmu support
>>> in guest vm. There are several reasons to justify this option. First
>>> vpmu can be problematic for cross-migration between different SoC as
>>> perf counters is architecture-dependent. It is more flexible to
>>> have an option to turn it on/off. Secondly it matches the -cpu pmu
>>> option in libivrt. This patch has been tested on both DT/ACPI modes.
>>
>>
>> What particular two systems are you trying to migrate between?
>
> One example: APM's Mustang has 5 perf counters while AMD's Seattle has 7
> counters.

Right; this is a cross-implementation migration, which isn't
supposed to work at the moment, and more will be required for
it to work than just pmu on/off.

thanks
-- PMM