From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AH8x227TZTVadTacnsCrYcIztU1nthpo7rvTrbEwJaspHgZZG+Ll3R+O8+NQ+a4DRmSSh2EMqRKf ARC-Seal: i=1; a=rsa-sha256; t=1516988070; cv=none; d=google.com; s=arc-20160816; b=lFwOVu8AZ/7S4JXILxri+eNxTgyCndB8+gASSSiJLqj9tfBNBlRpFQANQHcev/Il5O jvh2jghMg9CB8y2a7WoGjmV3VUKwH4hQDpKv3KlV+zJrmvJS1HOIgFGKoRQnvg/zk/A7 e8zWzM2IvW4bL0+bRYXb2AxjEQ/gV57xiJDFVHj/U4t6heH+qUw/hCik7zNN7Mrv3Dfb 9WaSBMALD2ypTKYRrDepJd/KLuMQpCgMddzCWvqkaV+vhQGluvbWWkzd2ywAqUO157gw nKgi8mwA1KDCMgESSan9bAuw7bMh/zK0pOeVcZ93GiAqaOCq1N9wx4mdmPdHL80Cb3wK aKRA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=mime-version:content-transfer-encoding:spamdiagnosticmetadata :spamdiagnosticoutput:msip_labels:content-language:accept-language :in-reply-to:references:message-id:date:thread-index:thread-topic :subject:cc:to:from:dkim-signature:arc-authentication-results; bh=9vvz9BUwWFNYuUHBgEjXPZ66/GrZ7m41uYL4KFAl6CA=; b=SX2R/c2EOtomfmgKRKaej5DonOqlM8sD23brcP7sWWgx1jZtjp7b8PNOWyCQQfb02D 2O0x9R2nbNb2Hyno/JwJn+Np74v9pouvqeREF5kvjHDkAEJ4CUwF6eEBPqeTQ6/k2MLg FtKFFajoMFZtPR30VwW35lBqQt952LnfHA1qAOPn4D2NcwFgCfUT9g0vonWLLxQhKF6i q2irqWrnqGEkyQB8utytMBFhB2Wpy0rG1stU9kPM6wdOnTPA1Q/naMTrbL1Cvgktg3oN MzqWoKe0JuIaYiHdXNXfMZkDPI3ZWjlwfOIQbCAqWHQMcMOCBjXFamFUKaBheIcCjpZv FDJg== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@microsoft.com header.s=selector1 header.b=lT8XczcB; spf=pass (google.com: domain of michael.h.kelley@microsoft.com designates 104.47.36.121 as permitted sender) smtp.mailfrom=Michael.H.Kelley@microsoft.com; dmarc=pass (p=REJECT sp=REJECT dis=NONE) header.from=microsoft.com Authentication-Results: mx.google.com; dkim=pass header.i=@microsoft.com header.s=selector1 header.b=lT8XczcB; spf=pass (google.com: domain of michael.h.kelley@microsoft.com designates 104.47.36.121 as permitted sender) smtp.mailfrom=Michael.H.Kelley@microsoft.com; dmarc=pass (p=REJECT sp=REJECT dis=NONE) header.from=microsoft.com From: "Michael Kelley (EOSG)" To: Greg KH CC: "linux-kernel@vger.kernel.org" , "devel@linuxdriverproject.org" , "olaf@aepfle.de" , "apw@canonical.com" , "vkuznets@redhat.com" , "jasowang@redhat.com" , "leann.ogasawara@canonical.com" , "marcelo.cerri@canonical.com" , Stephen Hemminger , "KY Srinivasan" , "x86@kernel.org" , "jrp@pun.org" Subject: RE: [PATCH v2 char-misc 1/1] Drivers: hv: vmbus: Implement Direct Mode for stimer0 Thread-Topic: [PATCH v2 char-misc 1/1] Drivers: hv: vmbus: Implement Direct Mode for stimer0 Thread-Index: AQHTk9CmEe7LRTvigUWlEDYDqcN9U6OEXsuAgAIN1EA= Date: Fri, 26 Jan 2018 17:34:28 +0000 Message-ID: References: <20180122222929.3762-1-mikelley@exchange.microsoft.com> <20180125095939.GA16968@kroah.com> In-Reply-To: <20180125095939.GA16968@kroah.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: msip_labels: MSIP_Label_f42aa342-8706-4288-bd11-ebb85995028c_Enabled=True; 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devel@linuxdriverproject.org; olaf@aepf= le.de; > apw@canonical.com; vkuznets@redhat.com; jasowang@redhat.com; > leann.ogasawara@canonical.com; marcelo.cerri@canonical.com; Stephen Hemmi= nger > ; KY Srinivasan ; x86@kernel.o= rg; > jrp@pun.org > Subject: Re: [PATCH v2 char-misc 1/1] Drivers: hv: vmbus: Implement Direc= t Mode for stimer0 >=20 > On Mon, Jan 22, 2018 at 03:29:29PM -0700, mikelley@exchange.microsoft.com= wrote: > > +/* > > + * If false, we're using the old mechanism for stimer0 interrupts > > + * where it sends a VMbus message when it expires. The old > > + * mechanism is used if Direct Mode is explicitly disabled > > + * by the module parameter, or on older versions of Hyper-V > > + * that don't support Direct Mode. While Hyper-V provides > > + * four stimer's per CPU, Linux uses only stimer0. > > + */ > > +static bool direct_mode_enabled =3D true; > > +module_param(direct_mode_enabled, bool, 0444); > > +MODULE_PARM_DESC(direct_mode_enabled, > > + "Set to N to disable stimer Direct Mode."); >=20 > Ick ick ick. How is a distro or user supposed to know if/when to enable > this and not to enable it? This isn't ok, can you please make this > "automatic" to always do the right thing based on what it is running on? To be clear, this patch already does the "automatic" thing based on the capabilities of the hypervisor. But it's often handy to be able to overrid= e the automatic behavior without having to rebuild the kernel. >=20 > Module parameters are not a good idea as they are impossible to maintain > and document and use over time. Please never add new ones to the > kernel. >=20 Is there a better alternative for providing an "override" capability? Having an override isn't super important in this case, so I'll drop the parameter, but it would be nice to have something easier than a rebuild. Michael > thanks, >=20 > greg k-h