From patchwork Fri Apr 23 18:17:26 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jing Zhang X-Patchwork-Id: 426499 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 94ADBC4361B for ; Fri, 23 Apr 2021 18:17:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 56E5761463 for ; Fri, 23 Apr 2021 18:17:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243653AbhDWSSP (ORCPT ); Fri, 23 Apr 2021 14:18:15 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36618 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232582AbhDWSSO (ORCPT ); Fri, 23 Apr 2021 14:18:14 -0400 Received: from mail-pg1-x54a.google.com (mail-pg1-x54a.google.com [IPv6:2607:f8b0:4864:20::54a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0CF6FC061756 for ; Fri, 23 Apr 2021 11:17:36 -0700 (PDT) Received: by mail-pg1-x54a.google.com with SMTP id t64-20020a6381430000b029020997d0fbb4so9333579pgd.22 for ; Fri, 23 Apr 2021 11:17:36 -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=x+yfWaSW+BpBYPoDL239kz1uEy2e3te6Z7USsJzuwP4=; b=dD9VyS5nwp9siCWdA7dB6wH7OAAFfSXwapSGOmrcfGrR1vxV0B8X+c6FtiymJBda2z +iBcP16vI5xBbq3YIhufM4+XoBK6BCQWYXRtkXyj9m36zS7D3mNGfXsuxy9yHasqAQPo o0XdMK+pXWdnyzJLrT2Fu53JiDMjUn5/kvUsLWik7Ym0UOE0KOkKe0lK9uk8hN+BPosQ JM6HsYTyDAdhibjuWYcT8fFVuIUMX/iQz8WY2xB5xLgWinWxiVyKyeUq54gDXQlYNERp HsfDwiCZV40t/X9Cp6kvNFTyt7JfAhkBAGeFpEsJOgPdmYRxD4I9dx2ESkkkb/9+3nJX NgVg== 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=x+yfWaSW+BpBYPoDL239kz1uEy2e3te6Z7USsJzuwP4=; b=Ps6BlFxW2oFeuSNURjC4oy6eFYxVvnVP5PVVagoZPHg2dyijCp4leLhS4j4F4gha3Y zhId8FAJFCJGik2VaYSDzi22CLq8kd7N2hEKkXgXgQZR8eXrxVIE1TsrCP+oO4n+j4n7 98Er9YS/6/lmmlk3rruaLwc074tl8rzVrPbS0SqVKVxMY3034/Oea4JmF5WQ+kHK96xB KSYkLzHOIEVjwd9LRgmyS48NL002C8Ywe9CJSnwmWcpdZ7ibEgccdmbWUCH9LRB/Ebr3 0zMWlDUXU1KQ+XPkkJuFkWnWriPCfh1MDACj4cwJbdcGfVS+csnc/CojpTbGtbrQmXvg gYxQ== X-Gm-Message-State: AOAM530QJzXZYdwaxxj3tVcg+I++obqheMEUpLCzyRFV16sSt67MFmYT CDriDGgAdHrDCqpxRCGpdkkurka5FXAUF4HCWQ== X-Google-Smtp-Source: ABdhPJw6P1yHcm0BYKpv2XtSaF51RcLGN0KBVTrEdDa1Nq2aeTtzmGfy9PryuxguZot/0mCYPJ2e/gpUtsQ8ugLz3w== X-Received: from jgzg.c.googlers.com ([fda3:e722:ac3:10:7f:e700:c0a8:1acf]) (user=jingzhangos job=sendgmr) by 2002:a62:e90c:0:b029:203:90f:6f34 with SMTP id j12-20020a62e90c0000b0290203090f6f34mr5125051pfh.29.1619201855484; Fri, 23 Apr 2021 11:17:35 -0700 (PDT) Date: Fri, 23 Apr 2021 18:17:26 +0000 In-Reply-To: <20210423181727.596466-1-jingzhangos@google.com> Message-Id: <20210423181727.596466-4-jingzhangos@google.com> Mime-Version: 1.0 References: <20210423181727.596466-1-jingzhangos@google.com> X-Mailer: git-send-email 2.31.1.498.g6c1eba8ee3d-goog Subject: [PATCH v3 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 Cc: Jing Zhang Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org Signed-off-by: Jing Zhang --- Documentation/virt/kvm/api.rst | 171 +++++++++++++++++++++++++++++++++ 1 file changed, 171 insertions(+) diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst index 8d614a577e43..faceadc2bd66 100644 --- a/Documentation/virt/kvm/api.rst +++ b/Documentation/virt/kvm/api.rst @@ -5021,6 +5021,169 @@ 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_STATS_GETFD +--------------------- + +: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 after a system boot. +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 +KVM 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 after a system boot. It is +an array of ``struct kvm_stats_desc`` as below:: + + #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_SCALE_SHIFT 8 + #define KVM_STATS_SCALE_MASK (0xF << KVM_STATS_SCALE_SHIFT) + #define KVM_STATS_SCALE_POW10 (0x0 << KVM_STATS_SCALE_SHIFT) + #define KVM_STATS_SCALE_POW2 (0x1 << KVM_STATS_SCALE_SHIFT) + #define KVM_STATS_SCALE_MAX KVM_STATS_SCALE_POW2 + + struct kvm_stats_desc { + __u32 flags; + __s16 exponent; + __u16 size; + __u32 unused1; + __u32 unused2; + __u8 name[0]; + }; + +The ``flags`` field contains the type and unit of the statistics data described +by this descriptor. The following flags are supported: + * ``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. + * ``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_SCALE_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_SCALE_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_SCALE_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``. + +The ``exponent`` field is the scale of corresponding statistics data. It has two +values as follows: + * ``KVM_STATS_SCALE_POW10`` + The scale is based on power of 10. It is used for measurement of time and + CPU clock cycles. + * ``KVM_STATS_SCALE_POW2`` + The scale is based on power of 2. It is used for measurement of memory size. + +The ``size`` field is the number of values of this statistics data. It is in the +unit of ``unsigned long`` for VCPU or ``__u64`` for VM. + +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 ======================== @@ -6888,3 +7051,11 @@ depends on the individual hypercall. Right now, the only bit that can be set is bit 12, corresponding to KVM_HC_PAGE_ENC_STATUS. The hypercall returns ENOSYS if bit 12 is not set or KVM_CAP_EXIT_HYPERCALL is not enabled. + +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.