From: Andrea Bolognani <abologna@redhat.com>
To: Peter Maydell <peter.maydell@linaro.org>
Cc: Andrew Jones <drjones@redhat.com>, qemu-arm <qemu-arm@nongnu.org>,
QEMU Developers <qemu-devel@nongnu.org>,
Shannon Zhao <shannon.zhao@linaro.org>
Subject: Re: [Qemu-arm] [Qemu-devel] [PATCH RFC 1/1] arm64: add an option to turn on/off vpmu support
Date: Mon, 01 Aug 2016 16:55:01 +0200 [thread overview]
Message-ID: <1470063301.3971.15.camel@redhat.com> (raw)
In-Reply-To: <CAFEAcA97p9GFrp+tX3pwqeVaSxjxVwuPvCAgZt5aYd_Yk+mGnA@mail.gmail.com>
On Mon, 2016-08-01 at 14:32 +0100, Peter Maydell wrote:
> > 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.
Doesn't look like the pmu option works like that on x86,
though, unless I'm missing something.
I have a guest running with
-cpu pentium,pmu=on
and I can't see hardware perf events from inside the guest,
eg. dmesg reports
Performance Events: no PMU driver, software events only.
and perf tells me
<not supported> instructions
<not supported> branches
...
I'm not sure whether that's because the PMU is being
emulated but the kernel doesn't have a driver for it, or
whether it's not being emulated at all. Any way to find
out?
--
Andrea Bolognani / Red Hat / Virtualization
WARNING: multiple messages have this Message-ID (diff)
From: Andrea Bolognani <abologna@redhat.com>
To: Peter Maydell <peter.maydell@linaro.org>
Cc: Andrew Jones <drjones@redhat.com>, Wei Huang <wei@redhat.com>,
qemu-arm <qemu-arm@nongnu.org>,
QEMU Developers <qemu-devel@nongnu.org>,
Shannon Zhao <shannon.zhao@linaro.org>
Subject: Re: [Qemu-devel] [PATCH RFC 1/1] arm64: add an option to turn on/off vpmu support
Date: Mon, 01 Aug 2016 16:55:01 +0200 [thread overview]
Message-ID: <1470063301.3971.15.camel@redhat.com> (raw)
In-Reply-To: <CAFEAcA97p9GFrp+tX3pwqeVaSxjxVwuPvCAgZt5aYd_Yk+mGnA@mail.gmail.com>
On Mon, 2016-08-01 at 14:32 +0100, Peter Maydell wrote:
> > 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.
Doesn't look like the pmu option works like that on x86,
though, unless I'm missing something.
I have a guest running with
-cpu pentium,pmu=on
and I can't see hardware perf events from inside the guest,
eg. dmesg reports
Performance Events: no PMU driver, software events only.
and perf tells me
<not supported> instructions
<not supported> branches
...
I'm not sure whether that's because the PMU is being
emulated but the kernel doesn't have a driver for it, or
whether it's not being emulated at all. Any way to find
out?
--
Andrea Bolognani / Red Hat / Virtualization
next prev parent reply other threads:[~2016-08-01 14:55 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-07-28 16:38 [Qemu-arm] [PATCH RFC 1/1] arm64: add an option to turn on/off vpmu support Wei Huang
2016-07-28 16:38 ` [Qemu-devel] " Wei Huang
2016-07-29 0:59 ` [Qemu-arm] " Shannon Zhao
2016-07-29 0:59 ` Shannon Zhao
2016-07-29 6:54 ` [Qemu-arm] " Andrew Jones
2016-07-29 6:54 ` Andrew Jones
2016-07-29 15:07 ` [Qemu-arm] " Wei Huang
2016-07-29 15:07 ` Wei Huang
2016-07-29 15:29 ` [Qemu-arm] " Peter Maydell
2016-07-29 15:29 ` Peter Maydell
2016-08-01 12:04 ` [Qemu-arm] " Andrea Bolognani
2016-08-01 12:04 ` Andrea Bolognani
2016-08-01 13:08 ` [Qemu-arm] " Andrew Jones
2016-08-01 13:08 ` Andrew Jones
2016-08-01 13:16 ` [Qemu-arm] " Peter Maydell
2016-08-01 13:16 ` Peter Maydell
2016-08-01 13:26 ` [Qemu-arm] " Andrea Bolognani
2016-08-01 13:26 ` Andrea Bolognani
2016-08-01 13:32 ` [Qemu-arm] " Peter Maydell
2016-08-01 13:32 ` Peter Maydell
2016-08-01 14:55 ` Andrea Bolognani [this message]
2016-08-01 14:55 ` Andrea Bolognani
2016-08-13 6:06 ` [Qemu-arm] " Wei Huang
2016-08-13 6:06 ` Wei Huang
2016-08-15 9:24 ` [Qemu-arm] " Andrea Bolognani
2016-08-15 9:24 ` Andrea Bolognani
2016-07-29 7:57 ` [Qemu-arm] " Peter Maydell
2016-07-29 7:57 ` [Qemu-devel] " Peter Maydell
2016-07-29 15:08 ` [Qemu-arm] " Wei Huang
2016-07-29 15:08 ` [Qemu-devel] " Wei Huang
2016-07-29 15:25 ` [Qemu-arm] " Peter Maydell
2016-07-29 15:25 ` [Qemu-devel] " Peter Maydell
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