From mboxrd@z Thu Jan 1 00:00:00 1970 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=-6.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 22076C433DB for ; Thu, 18 Mar 2021 14:53:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DDE4A64F01 for ; Thu, 18 Mar 2021 14:53:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231305AbhCROwi (ORCPT ); Thu, 18 Mar 2021 10:52:38 -0400 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:59097 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229960AbhCROwf (ORCPT ); Thu, 18 Mar 2021 10:52:35 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1616079149; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=ECZj1OY6qFwHdJt8CU1kR6qrjpoCi85QI/OBr1imPwQ=; b=T5i9tRoFKyXYxyIIKRq8hA2AFFnDFPqqHqiXsoXO0cvxuCwhPl8g5gK8Sh/zF+v1k1My2T wk7Z3z3D3YAHOz5s3qH6UKtXZjuz9GxZmivujOMB3ALncJBxdxzq1zPunmmWpGAqgRcReG zSQpL2HrTlB9lQcT7BeoCaHhnpkZ9Yo= Received: from mail-ed1-f70.google.com (mail-ed1-f70.google.com [209.85.208.70]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-404-y5jbRJjYOoW8-MYAyshTWg-1; Thu, 18 Mar 2021 10:52:27 -0400 X-MC-Unique: y5jbRJjYOoW8-MYAyshTWg-1 Received: by mail-ed1-f70.google.com with SMTP id h2so21235098edw.10 for ; Thu, 18 Mar 2021 07:52:27 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:in-reply-to:references:date :message-id:mime-version; bh=ECZj1OY6qFwHdJt8CU1kR6qrjpoCi85QI/OBr1imPwQ=; b=SvUGLMFsLmSDYgWmXbL4fuOEJPA0qggXoS4dQSNI9azFgsmChN84Ewil/FYFWG9WhJ KexPv7MUdt9oeVzmPaWudQ8/tm9mS88KskR5E/81t8r9mk2eHgU+jWBU9QmHmUnfA5+8 N9jl0qXL17jl8rxE8OOzFHyCZmbI/JQVBAvwnV6J4FSf1OFMEKNLNDIIwQMaBwExOLOE NdyvdHJ6liEUegquhEfvPF2qtXMbGmae/XsGRgoIYy1ckfieBChm7xHOmF1OeMcg7pVd 2G4A4jcHKOnIgbw31Zy3g9qwPHKZ8ZO1ArinE8ZKMB5ewXJPVgZ+IG65D0VImun4RhuE ceqg== X-Gm-Message-State: AOAM532Hd3Y31di7OUB9/frSN/HdUh4H4dACy80mjuo2TlhDzIa9iqZg ieem1cNb25iv8LokYC8iZVWJ7dHty7P+AYndq6rvJEXkXACgVcVSSYGbb0fmBSpDW3lm8xkPpcF VOCU/ZHN0z3Oi X-Received: by 2002:a50:f38f:: with SMTP id g15mr4066095edm.262.1616079146854; Thu, 18 Mar 2021 07:52:26 -0700 (PDT) X-Google-Smtp-Source: ABdhPJz1N0WUuZKABYtGP3i2mz58USiSdMym4kqMNeWOUyf3jVyqeXAfmV1mefVw/SuNQ/pYAJSYhg== X-Received: by 2002:a50:f38f:: with SMTP id g15mr4066082edm.262.1616079146666; Thu, 18 Mar 2021 07:52:26 -0700 (PDT) Received: from vitty.brq.redhat.com (g-server-2.ign.cz. [91.219.240.2]) by smtp.gmail.com with ESMTPSA id a22sm2086920ejr.89.2021.03.18.07.52.26 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 18 Mar 2021 07:52:26 -0700 (PDT) From: Vitaly Kuznetsov To: Paolo Bonzini , kvm@vger.kernel.org Cc: Sean Christopherson , Wanpeng Li , Jim Mattson , Marcelo Tosatti Subject: Re: [PATCH v2 6/4] selftests: kvm: Add basic Hyper-V clocksources tests In-Reply-To: <1176f351-220d-003e-2cae-65f0b42c8f18@redhat.com> References: <20210316143736.964151-1-vkuznets@redhat.com> <20210318140949.1065740-1-vkuznets@redhat.com> <1176f351-220d-003e-2cae-65f0b42c8f18@redhat.com> Date: Thu, 18 Mar 2021 15:52:25 +0100 Message-ID: <8735ws7bva.fsf@vitty.brq.redhat.com> MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Paolo Bonzini writes: > On 18/03/21 15:09, Vitaly Kuznetsov wrote: >> +static inline void check_tsc_msr_tsc_page(struct ms_hyperv_tsc_page *tsc_page) >> +{ >> + u64 r1, r2, t1, t2; >> + s64 delta_ns; >> + >> + /* Compare TSC page clocksource with HV_X64_MSR_TIME_REF_COUNT */ >> + t1 = mul_u64_u64_shr64(rdtsc(), tsc_page->tsc_scale) + tsc_page->tsc_offset; >> + r1 = rdmsr(HV_X64_MSR_TIME_REF_COUNT); >> + nop_loop(); >> + t2 = mul_u64_u64_shr64(rdtsc(), tsc_page->tsc_scale) + tsc_page->tsc_offset; >> + r2 = rdmsr(HV_X64_MSR_TIME_REF_COUNT); >> + >> + delta_ns = ((r2 - r1) - (t2 - t1)) * 100; >> + if (delta_ns < 0) >> + delta_ns = -delta_ns; >> + >> + /* 1% tolerance */ >> + GUEST_ASSERT(delta_ns * 100 < (t2 - t1) * 100); >> +} >> + > > I think you should also be able to check r1 and r2 individually, not > just r1 and r2. Is that correct? Right, we could've checked r1 == t1 and r2 == t2 actually (with some tiny margin of course). Let me try that. -- Vitaly