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

From: Peter Maydell
Subject: Re: [Qemu-arm] [PATCH RFC 1/1] arm64: add an option to turn on/off vpmu support
Date: Fri, 29 Jul 2016 16:25:53 +0100

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.

-- PMM

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