From: "Daniel P. Berrangé" <berrange@redhat.com>
To: Zhao Liu <zhao1.liu@intel.com>
Cc: Shaoqin Huang <shahuang@redhat.com>,
qemu-arm@nongnu.org, Eric Auger <eauger@redhat.com>,
Peter Maydell <peter.maydell@linaro.org>,
Paolo Bonzini <pbonzini@redhat.com>,
Thomas Huth <thuth@redhat.com>,
Laurent Vivier <lvivier@redhat.com>,
qemu-devel@nongnu.org, kvm@vger.kernel.org,
Zhenyu Wang <zhenyu.z.wang@intel.com>,
Dapeng Mi <dapeng1.mi@intel.com>
Subject: Re: [PATCH v9] arm/kvm: Enable support for KVM_ARM_VCPU_PMU_V3_FILTER
Date: Thu, 9 May 2024 10:39:33 +0100 [thread overview]
Message-ID: <ZjyZ1ZV7BGME_bY9@redhat.com> (raw)
In-Reply-To: <Zjyb43JqMZA+bO4r@intel.com>
On Thu, May 09, 2024 at 05:48:19PM +0800, Zhao Liu wrote:
> Hi Daniel & Shaoqin,
>
> Since x86 also needs to implement PMU filter feature, though it uses
> the different KVM ioctl, we can still make the QEMU API as general as
> possible.
>
> To move forward with both ARM and x86, I'd like to discuss my API
> thinking with you. ;-)
>
> On Mon, Apr 15, 2024 at 06:29:25PM +0100, Daniel P. Berrangé wrote:
> > Date: Mon, 15 Apr 2024 18:29:25 +0100
> > From: "Daniel P. Berrangé" <berrange@redhat.com>
> > Subject: Re: [PATCH v9] arm/kvm: Enable support for
> > KVM_ARM_VCPU_PMU_V3_FILTER
> >
> > On Mon, Apr 08, 2024 at 10:49:40PM -0400, Shaoqin Huang wrote:
> > > The KVM_ARM_VCPU_PMU_V3_FILTER provides the ability to let the VMM decide
> > > which PMU events are provided to the guest. Add a new option
> > > `kvm-pmu-filter` as -cpu sub-option to set the PMU Event Filtering.
> > > Without the filter, all PMU events are exposed from host to guest by
> > > default. The usage of the new sub-option can be found from the updated
> > > document (docs/system/arm/cpu-features.rst).
> > >
> > > Here is an example which shows how to use the PMU Event Filtering, when
> > > we launch a guest by use kvm, add such command line:
> > >
> > > # qemu-system-aarch64 \
> > > -accel kvm \
> > > -cpu host,kvm-pmu-filter="D:0x11-0x11"
> >
> > I'm still against implementing this one-off custom parsed syntax
> > for kvm-pmu-filter values. Once this syntax exists, we're locked
> > into back-compatibility for multiple releases, and it will make
> > a conversion to QAPI/JSON harder.
>
> Daniel, I understand you mean the new specific string format makes
> external API support more complicated, right?
>
> What about the following options:
>
> 1. Firstly, add a feature flag option in "-cpu" to enable kvm_filter
> feature for CPU:
>
> -cpu host,kvm-pmu-filter
>
> 2. Then use "-object kvm-pmu-event" to configure PMU event properties.
> Since x86's PMU filter has very complex encoding rules, we need the
> following three variants (one for general case, the other two are x86
> specific):
>
> - General format:
> -object kvm-pmu-event,action=[allowed|denied],events=[event-list]
>
> e.g, as Shaoqin's example,
> -object kvm-pmu-event,action=allowed,events=0x11-0x11,0x23-0x23
> -object kvm-pmu-event,action=denied,events=0x23-0x3a
>
> - x86 raw_event encoding format (for single raw format event encoding):
> -object kvm-pmu-event,action=[allowed|denied],mode=0,select="0x01",
> umask="0x3c",fixed-bitmap="0xffffffff"
>
> - x86 masked_event encoding format (for mutiple masked event encoding):
> -object kvm-pmu-event,action=[allowed|denied],mode=masked,select="0x01",
> mask="0x3c",match="0x11",exclude=true|false
>
> The whole API architecture looks more complex, but has the advantage of
> being as general as possible and avoiding the introduction of new string
> format parsing.
>
> What do you think? Because the most important thing about this feature
> is the API design, welcome your comments!
Please describe it in terms of a QAPI definition, as that's what we're
striving for with all QEMU public interfaces. Once the QAPI design is
agreed, then the -object mapping is trivial, as -object's JSON format
supports arbitrary QAPI structures.
With regards,
Daniel
--
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next prev parent reply other threads:[~2024-05-09 9:40 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-09 2:49 [PATCH v9] arm/kvm: Enable support for KVM_ARM_VCPU_PMU_V3_FILTER Shaoqin Huang
2024-04-09 5:33 ` Thomas Huth
2024-04-09 7:47 ` Shaoqin Huang
2024-04-10 6:07 ` Thomas Huth
2024-04-16 15:17 ` Cornelia Huck
2024-04-15 17:29 ` Daniel P. Berrangé
2024-05-07 9:33 ` Shaoqin Huang
2024-05-09 9:48 ` Zhao Liu
2024-05-09 9:39 ` Daniel P. Berrangé [this message]
2024-05-13 6:52 ` Zhao Liu
2024-05-15 16:47 ` Daniel P. Berrangé
2024-05-27 6:41 ` Shaoqin Huang
2024-05-27 10:24 ` Zhao Liu
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