From patchwork Thu Jun 3 21:14:25 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jing Zhang X-Patchwork-Id: 453637 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-26.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER, INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, SPF_PASS, USER_AGENT_GIT, USER_IN_DEF_DKIM_WL autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0952FC47097 for ; Thu, 3 Jun 2021 21:15:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DE4C5613EA for ; Thu, 3 Jun 2021 21:15:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230153AbhFCVRV (ORCPT ); Thu, 3 Jun 2021 17:17:21 -0400 Received: from mail-pl1-f201.google.com ([209.85.214.201]:54905 "EHLO mail-pl1-f201.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230054AbhFCVRV (ORCPT ); Thu, 3 Jun 2021 17:17:21 -0400 Received: by mail-pl1-f201.google.com with SMTP id a6-20020a1709027d86b02901019f88b046so3197857plm.21 for ; Thu, 03 Jun 2021 14:15:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=7lYIpwAKoJhaiEM5+z+3PAhyaX8WxzO9xGjhTMMBn6o=; b=ULlQHn6l+FLbaUJUHMTK59zH6EOX/QCltF6COyCi4rht212Z229rZUqodny+KM5WnZ H4nYmompfM9c7vr65EfJ78ZF9BgAq7WiDfVgYoXBIG0DT/KkY9dTQBQS2rGl+rHttidG e83uGFKsR7j09FdI/A9ojDIBNXKPC4MugMjUGSuyN/9XJx3hJJlWYYndhI0AKVmPl8b2 c0VezAqV1T0bNgnnwzCH/Jdw4QwLnmyK1laKL2/pADfaKBENNio5JG2FMDhRKfTZYzM0 Y9nkH3luD2/Cbl0tlioDe4Kq/ZEvEfuKTvmTU9Ow2FiGap4X/ctdC5eXinskVii7ZcpV owuw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=7lYIpwAKoJhaiEM5+z+3PAhyaX8WxzO9xGjhTMMBn6o=; b=ciMCX9Poxe/Nw/QKYPUlxIWL5c1aqsn2rEFPrN1epYfakt4OBoHLY45MoKYk5aTHup yNB665cWXA20YDxAUaI5FRfCLrvuraKE00IP1oaZXHK7ZRyRxCDzp/J8S8nfu7vamdcb pnSbpTB6OStHq2KMCiSta0GQzf4dPx6YI+A3DPBHfae+CbwARM1O8f991rrX3Un0F22h SnVqW4lyy/djBgft1WrhA6ETBlnpYaMQnRk+B2uuhhZivsrM/2YsYc7BtewMX12j0h6L 2T+Kg4x5tSatszql+WH0t+8tBsUNHmK6EJPzfa9lciB5DzH8myPLbEHNc3Z1x6y6jHiE Dl4g== X-Gm-Message-State: AOAM531dQUQvKf8x0xAx/8Uj5MxD76aPaGtyvHCuZiBjFTbzUvzQVQ/9 y4SCOUSWg/66VxhEtCs4u2xYmWvbu5IM4HnUxA== X-Google-Smtp-Source: ABdhPJxm2Ps971hfhxdJtKL0dyd3QcZkfvN97SKKDEvs7HP7IoQvFmtzUjT/4kLxh0KJO+KAasT850cCUSK2/rdVNQ== X-Received: from jgzg.c.googlers.com ([fda3:e722:ac3:10:7f:e700:c0a8:1acf]) (user=jingzhangos job=sendgmr) by 2002:a05:6a00:813:b029:27f:fb6a:24b5 with SMTP id m19-20020a056a000813b029027ffb6a24b5mr1113724pfk.18.1622754875857; Thu, 03 Jun 2021 14:14:35 -0700 (PDT) Date: Thu, 3 Jun 2021 21:14:25 +0000 In-Reply-To: <20210603211426.790093-1-jingzhangos@google.com> Message-Id: <20210603211426.790093-4-jingzhangos@google.com> Mime-Version: 1.0 References: <20210603211426.790093-1-jingzhangos@google.com> X-Mailer: git-send-email 2.32.0.rc1.229.g3e70b5a671-goog Subject: [PATCH v7 3/4] KVM: stats: Add documentation for statistics data binary interface From: Jing Zhang To: KVM , KVMARM , LinuxMIPS , KVMPPC , LinuxS390 , Linuxkselftest , Paolo Bonzini , Marc Zyngier , James Morse , Julien Thierry , Suzuki K Poulose , Will Deacon , Huacai Chen , Aleksandar Markovic , Thomas Bogendoerfer , Paul Mackerras , Christian Borntraeger , Janosch Frank , David Hildenbrand , Cornelia Huck , Claudio Imbrenda , Sean Christopherson , Vitaly Kuznetsov , Jim Mattson , Peter Shier , Oliver Upton , David Rientjes , Emanuele Giuseppe Esposito , David Matlack , Ricardo Koller , Krish Sadhukhan Cc: Jing Zhang Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org Update KVM API documentation for binary statistics. Reviewed-by: David Matlack Reviewed-by: Ricardo Koller Signed-off-by: Jing Zhang Reviewed-by: Krish Sadhukhan --- Documentation/virt/kvm/api.rst | 180 +++++++++++++++++++++++++++++++++ 1 file changed, 180 insertions(+) diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst index 7fcb2fd38f42..550bfbdf611b 100644 --- a/Documentation/virt/kvm/api.rst +++ b/Documentation/virt/kvm/api.rst @@ -5034,6 +5034,178 @@ see KVM_XEN_VCPU_SET_ATTR above. The KVM_XEN_VCPU_ATTR_TYPE_RUNSTATE_ADJUST type may not be used with the KVM_XEN_VCPU_GET_ATTR ioctl. +4.130 KVM_GET_STATS_FD +--------------------- + +:Capability: KVM_CAP_STATS_BINARY_FD +:Architectures: all +:Type: vm ioctl, vcpu ioctl +:Parameters: none +:Returns: statistics file descriptor on success, < 0 on error + +Errors: + + ====== ====================================================== + ENOMEM if the fd could not be created due to lack of memory + EMFILE if the number of opened files exceeds the limit + ====== ====================================================== + +The file descriptor can be used to read VM/vCPU statistics data in binary +format. The file data is organized into three blocks as below: ++-------------+ +| Header | ++-------------+ +| Descriptors | ++-------------+ +| Stats Data | ++-------------+ + +The Header block is always at the start of the file. It is only needed to be +read one time for the lifetime of the file descriptor. +It is in the form of ``struct kvm_stats_header`` as below:: + + #define KVM_STATS_ID_MAXLEN 64 + + struct kvm_stats_header { + char id[KVM_STATS_ID_MAXLEN]; + __u32 name_size; + __u32 count; + __u32 desc_offset; + __u32 data_offset; + }; + +The ``id`` field is identification for the corresponding KVM statistics. For +VM statistics, it is in the form of "kvm-{kvm pid}", like "kvm-12345". For +VCPU statistics, it is in the form of "kvm-{kvm pid}/vcpu-{vcpu id}", like +"kvm-12345/vcpu-12". + +The ``name_size`` field is the size (byte) of the statistics name string +(including trailing '\0') appended to the end of every statistics descriptor. + +The ``count`` field is the number of statistics. + +The ``desc_offset`` field is the offset of the Descriptors block from the start +of the file indicated by the file descriptor. + +The ``data_offset`` field is the offset of the Stats Data block from the start +of the file indicated by the file descriptor. + +The Descriptors block is only needed to be read once for the lifetime of the +file descriptor. It is an array of ``struct kvm_stats_desc`` as shown in +below code block:: + + #define KVM_STATS_TYPE_SHIFT 0 + #define KVM_STATS_TYPE_MASK (0xF << KVM_STATS_TYPE_SHIFT) + #define KVM_STATS_TYPE_CUMULATIVE (0x0 << KVM_STATS_TYPE_SHIFT) + #define KVM_STATS_TYPE_INSTANT (0x1 << KVM_STATS_TYPE_SHIFT) + #define KVM_STATS_TYPE_MAX KVM_STATS_TYPE_INSTANT + + #define KVM_STATS_UNIT_SHIFT 4 + #define KVM_STATS_UNIT_MASK (0xF << KVM_STATS_UNIT_SHIFT) + #define KVM_STATS_UNIT_NONE (0x0 << KVM_STATS_UNIT_SHIFT) + #define KVM_STATS_UNIT_BYTES (0x1 << KVM_STATS_UNIT_SHIFT) + #define KVM_STATS_UNIT_SECONDS (0x2 << KVM_STATS_UNIT_SHIFT) + #define KVM_STATS_UNIT_CYCLES (0x3 << KVM_STATS_UNIT_SHIFT) + #define KVM_STATS_UNIT_MAX KVM_STATS_UNIT_CYCLES + + #define KVM_STATS_BASE_SHIFT 8 + #define KVM_STATS_BASE_MASK (0xF << KVM_STATS_BASE_SHIFT) + #define KVM_STATS_BASE_POW10 (0x0 << KVM_STATS_BASE_SHIFT) + #define KVM_STATS_BASE_POW2 (0x1 << KVM_STATS_BASE_SHIFT) + #define KVM_STATS_BASE_MAX KVM_STATS_BASE_POW2 + + struct kvm_stats_desc { + __u32 flags; + __s16 exponent; + __u16 size; + __u32 unused1; + __u32 unused2; + char name[0]; + }; + +The ``flags`` field contains the type and unit of the statistics data described +by this descriptor. The following flags are supported: + +Bits 0-3 of ``flags`` encode the type: + * ``KVM_STATS_TYPE_CUMULATIVE`` + The statistics data is cumulative. The value of data can only be increased. + Most of the counters used in KVM are of this type. + The corresponding ``count`` filed for this type is always 1. + * ``KVM_STATS_TYPE_INSTANT`` + The statistics data is instantaneous. Its value can be increased or + decreased. This type is usually used as a measurement of some resources, + like the number of dirty pages, the number of large pages, etc. + The corresponding ``count`` field for this type is always 1. + +Bits 4-7 of ``flags`` encode the unit: + * ``KVM_STATS_UNIT_NONE`` + There is no unit for the value of statistics data. This usually means that + the value is a simple counter of an event. + * ``KVM_STATS_UNIT_BYTES`` + It indicates that the statistics data is used to measure memory size, in the + unit of Byte, KiByte, MiByte, GiByte, etc. The unit of the data is + determined by the ``exponent`` field in the descriptor. The + ``KVM_STATS_BASE_POW2`` flag is valid in this case. The unit of the data is + determined by ``pow(2, exponent)``. For example, if value is 10, + ``exponent`` is 20, which means the unit of statistics data is MiByte, we + can get the statistics data in the unit of Byte by + ``value * pow(2, exponent) = 10 * pow(2, 20) = 10 MiByte`` which is + 10 * 1024 * 1024 Bytes. + * ``KVM_STATS_UNIT_SECONDS`` + It indicates that the statistics data is used to measure time/latency, in + the unit of nanosecond, microsecond, millisecond and second. The unit of the + data is determined by the ``exponent`` field in the descriptor. The + ``KVM_STATS_BASE_POW10`` flag is valid in this case. The unit of the data + is determined by ``pow(10, exponent)``. For example, if value is 2000000, + ``exponent`` is -6, which means the unit of statistics data is microsecond, + we can get the statistics data in the unit of second by + ``value * pow(10, exponent) = 2000000 * pow(10, -6) = 2 seconds``. + * ``KVM_STATS_UNIT_CYCLES`` + It indicates that the statistics data is used to measure CPU clock cycles. + The ``KVM_STATS_BASE_POW10`` flag is valid in this case. For example, if + value is 200, ``exponent`` is 4, we can get the number of CPU clock cycles + by ``value * pow(10, exponent) = 200 * pow(10, 4) = 2000000``. + +Bits 7-11 of ``flags`` encode the base: + * ``KVM_STATS_BASE_POW10`` + The scale is based on power of 10. It is used for measurement of time and + CPU clock cycles. + * ``KVM_STATS_BASE_POW2`` + The scale is based on power of 2. It is used for measurement of memory size. + +The ``exponent`` field is the scale of corresponding statistics data. For +example, if the unit is ``KVM_STATS_UNIT_BYTES``, the base is +``KVM_STATS_BASE_POW2``, the ``exponent`` is 10, then we know that the real +unit of the statistics data is KBytes a.k.a pow(2, 10) = 1024 bytes. + +The ``size`` field is the number of values of this statistics data. It is in the +unit of ``unsigned long`` for VM or ``__u64`` for VCPU. + +The ``unused1`` and ``unused2`` fields are reserved for future +support for other types of statistics data, like log/linear histogram. + +The ``name`` field points to the name string of the statistics data. The name +string starts at the end of ``struct kvm_stats_desc``. +The maximum length (including trailing '\0') is indicated by ``name_size`` +in ``struct kvm_stats_header``. + +The Stats Data block contains an array of data values of type ``struct +kvm_vm_stats_data`` or ``struct kvm_vcpu_stats_data``. It would be read by +user space periodically to pull statistics data. +The order of data value in Stats Data block is the same as the order of +descriptors in Descriptors block. + * Statistics data for VM:: + + struct kvm_vm_stats_data { + unsigned long value[0]; + }; + + * Statistics data for VCPU:: + + struct kvm_vcpu_stats_data { + __u64 value[0]; + }; + 5. The kvm_run structure ======================== @@ -6891,3 +7063,11 @@ This capability is always enabled. This capability indicates that the KVM virtual PTP service is supported in the host. A VMM can check whether the service is available to the guest on migration. + +8.33 KVM_CAP_STATS_BINARY_FD +---------------------------- + +:Architectures: all + +This capability indicates the feature that user space can create get a file +descriptor for every VM and VCPU to read statistics data in binary format.