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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0BE5FC77B73 for ; Tue, 6 Jun 2023 08:49:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237266AbjFFIt4 (ORCPT ); Tue, 6 Jun 2023 04:49:56 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41992 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237287AbjFFItu (ORCPT ); Tue, 6 Jun 2023 04:49:50 -0400 Received: from mail-qt1-x831.google.com (mail-qt1-x831.google.com [IPv6:2607:f8b0:4864:20::831]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 991E0EA for ; Tue, 6 Jun 2023 01:49:49 -0700 (PDT) Received: by mail-qt1-x831.google.com with SMTP id d75a77b69052e-3f9a81da5d7so184971cf.0 for ; Tue, 06 Jun 2023 01:49:49 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20221208; t=1686041389; x=1688633389; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:from:to:cc:subject:date :message-id:reply-to; bh=t+giJv4q8xwL1uh7HgsStC/LdZwc68W1gk/9rNonGFk=; b=KTDe/AQn2rkST076eM6v5NeyVIkELfJMgLhd3UE6bHtoPCbt4IzKswJOSTnqQah6QY DgTQzwoqnlCGth95pAtCNs3GhL0YWPM/JADH3ximdmt3+MgNngoeb/n0EyabLpR5y+71 HJ0Ek+LuMZ1i9dSmzeug0lH6HGfo0GzP/SOsNgnBznCdblikUrSPDi3X6e+6EfLw+UaU qzXxXlFKjF6xZALlNcR/BPqZOlHl176F/srAQwnfSbwUJfEmKP+cRL5OWKLJv6yEyONI CK9QelC0zIl/P4767IgxKvMUwyjvJWeauzqoGFqAddn8UbCIa1jIQ0R1fg/OGybu38s+ 4G4w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1686041389; x=1688633389; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=t+giJv4q8xwL1uh7HgsStC/LdZwc68W1gk/9rNonGFk=; b=jiNgf/5P048KZCC2i/9XksUUg5JSmxOOpZJU5zwbHjMolGv9ZqEaq90v2OeHMUhx0l ia6Z/sJhOUH37TqoO6OGUk+f/H6FUKz22zltP1nnPenq9HZp0Gg/ukXh8wlGX2gDf0aX FCl/+RmO7EXid1cSoOyyTy8knpHup7Oy1rpTesGLiFQ0EAmHxX9B3e2/Z+L4F6uz6FFO 2oYAV/uOtBgliahqw1bNflzELISLj1iSBNPeoDIxta4NUuDd6nh0jA3YiWtbkpJcNZtD E4WQ4l/kj9G8fM8W0h/YFcC2mItJfwo5+0lMDkz++h03ZKtQyBSFC6tfs6LtndBlE6I9 K5lg== X-Gm-Message-State: AC+VfDyE1uHkRRFo2kM3UQcW551cpyAUJwWm2vUrHOhhRlTXt6S72tOK p6vCB1EYnOiwnGJHuwYvvh2NI44sBqqYE4jgPcrRgw== X-Google-Smtp-Source: ACHHUZ6b9tVGLdvTytPaGPfvkZkX+F8ZZu9njisW9Mx1IQ18P7+fYLdg7lRbhYivfjwhC7Jy88/quTQtkOvdWpTm0Bc= X-Received: by 2002:ac8:7f03:0:b0:3f4:f841:df89 with SMTP id f3-20020ac87f03000000b003f4f841df89mr119162qtk.1.1686041388686; Tue, 06 Jun 2023 01:49:48 -0700 (PDT) MIME-Version: 1.0 References: <20230525180209.19497-1-james.morse@arm.com> <20230525180209.19497-13-james.morse@arm.com> In-Reply-To: <20230525180209.19497-13-james.morse@arm.com> From: Peter Newman Date: Tue, 6 Jun 2023 10:49:37 +0200 Message-ID: Subject: Re: [PATCH v4 12/24] x86/resctrl: Make resctrl_arch_rmid_read() retry when it is interrupted To: James Morse Cc: x86@kernel.org, linux-kernel@vger.kernel.org, Fenghua Yu , Reinette Chatre , Thomas Gleixner , Ingo Molnar , Borislav Petkov , H Peter Anvin , Babu Moger , shameerali.kolothum.thodi@huawei.com, D Scott Phillips OS , carl@os.amperecomputing.com, lcherian@marvell.com, bobo.shaobowang@huawei.com, tan.shaopeng@fujitsu.com, xingxin.hx@openanolis.org, baolin.wang@linux.alibaba.com, Jamie Iles , Xin Hao , dfustini@baylibre.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi James, On Thu, May 25, 2023 at 8:03=E2=80=AFPM James Morse w= rote: > +interrupted: > + am =3D get_arch_mbm_state(hw_dom, rmid, eventid); > + if (am) > + start_msr_val =3D atomic64_read(&am->prev_msr); > + > ret =3D __rmid_read(rmid, eventid, &msr_val); > if (ret) > return ret; > > am =3D get_arch_mbm_state(hw_dom, rmid, eventid); > if (am) { > - am->chunks +=3D mbm_overflow_count(am->prev_msr, msr_val, > - hw_res->mbm_width); > - chunks =3D get_corrected_mbm_count(rmid, am->chunks); > - am->prev_msr =3D msr_val; > + old_msr_val =3D atomic64_cmpxchg(&am->prev_msr, start_msr= _val, > + msr_val); > + if (old_msr_val !=3D start_msr_val) > + goto interrupted; > + > + chunks =3D mbm_overflow_count(start_msr_val, msr_val, > + hw_res->mbm_width); > + atomic64_add(chunks, &am->chunks); > + > + chunks =3D get_corrected_mbm_count(rmid, > + atomic64_read(&am->chunk= s)); > } else { > chunks =3D msr_val; > } It looks like if __rmid_read() is interrupted by an occupancy counter read between writing QM_EVTSEL and reading QM_CTR, it will not perform any update to am->prev_msr, and the interrupted read will return the same counter value as in the interrupting read. Maybe there's something you can create to check that's updated unconditiona= lly? -Peter