On 08/01/2016 08:32 AM, Peter Maydell wrote: > On 1 August 2016 at 14:26, Andrea Bolognani <abolo...@redhat.com> wrote: >> On Mon, 2016-08-01 at 15:08 +0200, Andrew Jones wrote: >>>> I'm not sure a warning is enough: if I start a guest and >>>> explicitly ask for a PMU, I expect it to be there, or for >>>> the guest not to start at all. How does x86 behave in this >>>> regard? >>> >>> Peter had a good suggestion for this. We need to wrap the property >>> addition in an arm_feature check like the has_el3 property. That will >>> remove it from all cpu types that don't support it. >> >> Wouldn't that mean that you'd be unable to use >> >> -cpu foo,pmu=off >> >> if CPU model 'foo' doesn't support a PMU? I'd expect that >> to work. > > The current precedent (has_el3) doesn't work like that: if > foo isn't a CPU which can support EL3 then the property doesn't > exist, and it's an error to try to set it.
V1 sent. I tried to follow everyone's advice. See the following: * set default pmu=off * like el3, add a new feature ARM_FEATURE_HOST_PMU * "pmu" property becomes CPU dependent. Only cortex-a53/cortex-a57/host under certain mode support this option * change struct ARMCPU field name "has_pmu" ==> "has_host_pmu" because IMO "has_pmu" is misleading BTW answering Andrea's question above: "-cpu foo,pmu=off" won't be allowed in this patch if CPU "foo" doesn't support host-backed PMU. QEMU will fail to run in this case. Maybe this is what we want? Thanks, -Wei > > thanks > -- PMM >
