| Message ID | 20250409082649.14733-1-zhao1.liu@intel.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | accel/kvm: Support KVM PMU filter | expand |
Hi Zhao, I've added some code and test it on ARM64, it works very well. And after reviewing the code, it looks good to me. Reviewed-by: Shaoqin Huang <shahuang@redhat.com> On 4/9/25 4:26 PM, Zhao Liu wrote: > Hi all, > > Now I've converted the previous RFC (v2) to PATCH. > > Compared with RFC v2 [1], this version mianly have the following > changes: > * Make PMU related QAPIs accept decimal value instead of string. > * Introduce a three-level QAPI section to organize KVM PMU stuff. > * Fix QAPI related style issues. > * Rename "x86-default" format to "x86-select-umask". > > Current pmu-filter QOM design could meet the requirements of both x86 > and ARM sides. > > > Background > ========== > > I picked up Shaoqing's previous work [2] on the KVM PMU filter for arm, > and now is trying to support this feature for x86 with a JSON-compatible > API. > > While arm and x86 use different KVM ioctls to configure the PMU filter, > considering they all have similar inputs (PMU event + action), it is > still possible to abstract a generic, cross-architecture kvm-pmu-filter > object and provide users with a sufficiently generic or near-consistent > QAPI interface. > > That's what I did in this series, a new kvm-pmu-filter object, with the > API like: > > -object '{"qom-type":"kvm-pmu-filter","id":"f0","action":"allow","events":[{"format":"raw","code":196}]}' > > For x86, this object is inserted into kvm accelerator and is extended > to support fixed-counter and more formats ("x86-default" and > "x86-masked-entry"): > > -accel kvm,pmu-filter=f0 \ > -object '{"qom-type":"kvm-pmu-filter","id":"f0","action":"allow","x86-fixed-counter":0,"events":[{"format":"x86-masked-entry","select":196,"mask":255,"match":0,"exclude":true},{"format":"x86-masked-entry","select":197,"mask":255,"match":0,"exclude":true}]}' > > This object can still be added as the property to the arch CPU if it is > desired as a per CPU feature (as Shaoqin did for arm before). > > > Introduction > ============ > > > Formats supported in kvm-pmu-filter > ----------------------------------- > > This series supports 3 formats: > > * raw format (general format). > > This format indicates the code that has been encoded to be able to > index the PMU events, and which can be delivered directly to the KVM > ioctl. For arm, this means the event code, and for i386, this means > the raw event with the layout like: > > select high bit | umask | select low bits > > * x86-select-umask format (i386 specific) > > x86 commonly uses select&umask to identify PMU events, and this format > is used to support the select&umask. Then QEMU will encode select and > umask into a raw format code. > > * x86-masked-entry (i386 specific) > > This is a special format that x86's KVM_SET_PMU_EVENT_FILTER supports. > > > CPU property v.s. KVM property > ------------------------------ > > In Shaoqin's previous implementation [2], KVM PMU filter is made as a > arm CPU property. This is because arm uses a per CPU ioctl > (KVM_SET_DEVICE_ATTR) to configure KVM PMU filter. > > However, for x86, the dependent ioctl (KVM_SET_PMU_EVENT_FILTER) is per > VM. In the meantime, considering that for hybrid architecture, maybe in > the future there will be a new per vCPU ioctl, or there will be > practices to support filter fixed counter by configuring CPUIDs. > > Based on the above thoughts, for x86, it is not appropriate to make the > current per-VM ioctl-based PMU filter a CPU property. Instead, I make it > a kvm property and configure it via "-accel kvm,pmu-filter=obj_id". > > So in summary, it is feasible to use the KVM PMU filter as either a CPU > or a KVM property, depending on whether it is used as a CPU feature or a > VM feature. > > The kvm-pmu-filter object, as an abstraction, is general enough to > support filter configurations for different scopes (per-CPU or per-VM). > > [1]: https://lore.kernel.org/qemu-devel/20250122090517.294083-1-zhao1.liu@intel.com/ > [2]: https://lore.kernel.org/qemu-devel/20240409024940.180107-1-shahuang@redhat.com/ > > Thanks and Best Regards, > Zhao > --- > Zhao Liu (5): > qapi/qom: Introduce kvm-pmu-filter object > i386/kvm: Support basic KVM PMU filter > i386/kvm: Support event with select & umask format in KVM PMU filter > i386/kvm: Support event with masked entry format in KVM PMU filter > i386/kvm: Support fixed counter in KVM PMU filter > > MAINTAINERS | 2 + > accel/kvm/kvm-pmu.c | 177 +++++++++++++++++++++++++++++++++++++++ > accel/kvm/meson.build | 1 + > include/system/kvm-pmu.h | 51 +++++++++++ > include/system/kvm_int.h | 2 + > qapi/accelerator.json | 14 ++++ > qapi/kvm.json | 130 ++++++++++++++++++++++++++++ > qapi/meson.build | 1 + > qapi/qapi-schema.json | 1 + > qapi/qom.json | 3 + > qemu-options.hx | 67 ++++++++++++++- > target/i386/kvm/kvm.c | 176 ++++++++++++++++++++++++++++++++++++++ > 12 files changed, 624 insertions(+), 1 deletion(-) > create mode 100644 accel/kvm/kvm-pmu.c > create mode 100644 include/system/kvm-pmu.h > create mode 100644 qapi/accelerator.json > create mode 100644 qapi/kvm.json >
On Tue, Apr 15, 2025 at 03:49:59PM +0800, Shaoqin Huang wrote: > Date: Tue, 15 Apr 2025 15:49:59 +0800 > From: Shaoqin Huang <shahuang@redhat.com> > Subject: Re: [PATCH 0/5] accel/kvm: Support KVM PMU filter > > Hi Zhao, > > I've added some code and test it on ARM64, it works very well. > > And after reviewing the code, it looks good to me. > > Reviewed-by: Shaoqin Huang <shahuang@redhat.com> Thank you Shaoqin for your support! Regards, Zhao
Hi all, Now I've converted the previous RFC (v2) to PATCH. Compared with RFC v2 [1], this version mianly have the following changes: * Make PMU related QAPIs accept decimal value instead of string. * Introduce a three-level QAPI section to organize KVM PMU stuff. * Fix QAPI related style issues. * Rename "x86-default" format to "x86-select-umask". Current pmu-filter QOM design could meet the requirements of both x86 and ARM sides. Background ========== I picked up Shaoqing's previous work [2] on the KVM PMU filter for arm, and now is trying to support this feature for x86 with a JSON-compatible API. While arm and x86 use different KVM ioctls to configure the PMU filter, considering they all have similar inputs (PMU event + action), it is still possible to abstract a generic, cross-architecture kvm-pmu-filter object and provide users with a sufficiently generic or near-consistent QAPI interface. That's what I did in this series, a new kvm-pmu-filter object, with the API like: -object '{"qom-type":"kvm-pmu-filter","id":"f0","action":"allow","events":[{"format":"raw","code":196}]}' For x86, this object is inserted into kvm accelerator and is extended to support fixed-counter and more formats ("x86-default" and "x86-masked-entry"): -accel kvm,pmu-filter=f0 \ -object '{"qom-type":"kvm-pmu-filter","id":"f0","action":"allow","x86-fixed-counter":0,"events":[{"format":"x86-masked-entry","select":196,"mask":255,"match":0,"exclude":true},{"format":"x86-masked-entry","select":197,"mask":255,"match":0,"exclude":true}]}' This object can still be added as the property to the arch CPU if it is desired as a per CPU feature (as Shaoqin did for arm before). Introduction ============ Formats supported in kvm-pmu-filter ----------------------------------- This series supports 3 formats: * raw format (general format). This format indicates the code that has been encoded to be able to index the PMU events, and which can be delivered directly to the KVM ioctl. For arm, this means the event code, and for i386, this means the raw event with the layout like: select high bit | umask | select low bits * x86-select-umask format (i386 specific) x86 commonly uses select&umask to identify PMU events, and this format is used to support the select&umask. Then QEMU will encode select and umask into a raw format code. * x86-masked-entry (i386 specific) This is a special format that x86's KVM_SET_PMU_EVENT_FILTER supports. CPU property v.s. KVM property ------------------------------ In Shaoqin's previous implementation [2], KVM PMU filter is made as a arm CPU property. This is because arm uses a per CPU ioctl (KVM_SET_DEVICE_ATTR) to configure KVM PMU filter. However, for x86, the dependent ioctl (KVM_SET_PMU_EVENT_FILTER) is per VM. In the meantime, considering that for hybrid architecture, maybe in the future there will be a new per vCPU ioctl, or there will be practices to support filter fixed counter by configuring CPUIDs. Based on the above thoughts, for x86, it is not appropriate to make the current per-VM ioctl-based PMU filter a CPU property. Instead, I make it a kvm property and configure it via "-accel kvm,pmu-filter=obj_id". So in summary, it is feasible to use the KVM PMU filter as either a CPU or a KVM property, depending on whether it is used as a CPU feature or a VM feature. The kvm-pmu-filter object, as an abstraction, is general enough to support filter configurations for different scopes (per-CPU or per-VM). [1]: https://lore.kernel.org/qemu-devel/20250122090517.294083-1-zhao1.liu@intel.com/ [2]: https://lore.kernel.org/qemu-devel/20240409024940.180107-1-shahuang@redhat.com/ Thanks and Best Regards, Zhao --- Zhao Liu (5): qapi/qom: Introduce kvm-pmu-filter object i386/kvm: Support basic KVM PMU filter i386/kvm: Support event with select & umask format in KVM PMU filter i386/kvm: Support event with masked entry format in KVM PMU filter i386/kvm: Support fixed counter in KVM PMU filter MAINTAINERS | 2 + accel/kvm/kvm-pmu.c | 177 +++++++++++++++++++++++++++++++++++++++ accel/kvm/meson.build | 1 + include/system/kvm-pmu.h | 51 +++++++++++ include/system/kvm_int.h | 2 + qapi/accelerator.json | 14 ++++ qapi/kvm.json | 130 ++++++++++++++++++++++++++++ qapi/meson.build | 1 + qapi/qapi-schema.json | 1 + qapi/qom.json | 3 + qemu-options.hx | 67 ++++++++++++++- target/i386/kvm/kvm.c | 176 ++++++++++++++++++++++++++++++++++++++ 12 files changed, 624 insertions(+), 1 deletion(-) create mode 100644 accel/kvm/kvm-pmu.c create mode 100644 include/system/kvm-pmu.h create mode 100644 qapi/accelerator.json create mode 100644 qapi/kvm.json