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=-8.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS 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 A3B22C47088 for ; Wed, 26 May 2021 08:51:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7E15C6143C for ; Wed, 26 May 2021 08:51:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233277AbhEZIwb (ORCPT ); Wed, 26 May 2021 04:52:31 -0400 Received: from mail-ua1-f42.google.com ([209.85.222.42]:46894 "EHLO mail-ua1-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232617AbhEZIwa (ORCPT ); Wed, 26 May 2021 04:52:30 -0400 Received: by mail-ua1-f42.google.com with SMTP id h26so340746uab.13; Wed, 26 May 2021 01:50:59 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=ftj/o/FDlLZjvveU5gflHCydxVxy9/duOHSuWLsKuds=; b=gzUBebI1WuB/5fkUx1y0oflbKBO2nJRvgKevQ/1JqUA1aPixRsQ6XgY/E+PGl8YFDb v6YXbmpQFoXXfjX9RnX1PIAnnXPOlmmuqsSJMQ0/QwRjW0m6/lo/b5eEQKpLzDa+3K+G CpmFqw8dQUzeJORNcWefueRBdAD6znRBePDhcBH3aECy5Qdsoyzsncmz8AsvqDGnS/AT cexFtZLcaUFwLO/Fzu9ZkDc8UajoqK4yRvUiuv7XzGoalsHpBhiOTkV1rN6NxTTQcjBY PvOSA7EnnucGnAY+FjyX1LD+YuYYZF2+NL0gIIOeJa6W/n6S9MBy40PCx6KAIhnLaZxq mqrQ== X-Gm-Message-State: AOAM530/mpYKMt+3kw+JWnyAo4LXGfKlrxCVsg8sQoHi4cOYqB6jTpKD jQXOFBTcNNnAT46FiffZkFUL5RaZbFHpP6bwrfU3LpM8 X-Google-Smtp-Source: ABdhPJywUZ6Xwv+zij4MSQ000T5eibp+TpLy3YyyGoFqj+kf4ejbTke4WZLjWrCgAdHGlnISxwMlbpFtCE1QmEgp5j8= X-Received: by 2002:ab0:2a8b:: with SMTP id h11mr31904723uar.4.1622019058834; Wed, 26 May 2021 01:50:58 -0700 (PDT) MIME-Version: 1.0 References: <20210330145430.996981-1-maz@kernel.org> <20210330145430.996981-8-maz@kernel.org> <6c522f8116f54fa6f23a2d217d966c5a@kernel.org> <8735u9x6sb.wl-maz@kernel.org> <871r9tx5dq.wl-maz@kernel.org> In-Reply-To: <871r9tx5dq.wl-maz@kernel.org> From: Geert Uytterhoeven Date: Wed, 26 May 2021 10:50:47 +0200 Message-ID: Subject: Re: [PATCH v19 7/7] ptp: arm/arm64: Enable ptp_kvm for arm/arm64 To: Marc Zyngier Cc: jianyong.wu@arm.com, netdev , Yangbo Lu , John Stultz , Thomas Gleixner , Paolo Bonzini , seanjc@google.com, Richard Cochran , Mark Rutland , Will Deacon , Suzuki K Poulose , Andre Przywara , Steven Price , Lorenzo Pieralisi , Sudeep Holla , Linux Kernel Mailing List , Linux ARM , kvmarm@lists.cs.columbia.edu, KVM list , Steve Capper , justin.he@arm.com, Android Kernel Team Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Marc, On Wed, May 26, 2021 at 10:32 AM Marc Zyngier wrote: > On Wed, 26 May 2021 09:18:27 +0100, > Geert Uytterhoeven wrote: > > On Wed, May 26, 2021 at 10:01 AM Marc Zyngier wrote: > > > On Wed, 26 May 2021 08:52:42 +0100, > > > Geert Uytterhoeven wrote: > > > > On Tue, May 11, 2021 at 11:13 AM Marc Zyngier wrote: > > > > > On 2021-05-11 10:07, Geert Uytterhoeven wrote: > > > > > > On Tue, Mar 30, 2021 at 4:56 PM Marc Zyngier wrote: > > > > > >> From: Jianyong Wu > > > > > > > > > > > >> --- a/drivers/ptp/Kconfig > > > > > >> +++ b/drivers/ptp/Kconfig > > > > > >> @@ -108,7 +108,7 @@ config PTP_1588_CLOCK_PCH > > > > > >> config PTP_1588_CLOCK_KVM > > > > > >> tristate "KVM virtual PTP clock" > > > > > >> depends on PTP_1588_CLOCK > > > > > >> - depends on KVM_GUEST && X86 > > > > > >> + depends on (KVM_GUEST && X86) || (HAVE_ARM_SMCCC_DISCOVERY && > > > > > >> ARM_ARCH_TIMER) > > > > > > > > > > > > Why does this not depend on KVM_GUEST on ARM? > > > > > > I.e. shouldn't the dependency be: > > > > > > > > > > > > KVM_GUEST && (X86 || (HAVE_ARM_SMCCC_DISCOVERY && ARM_ARCH_TIMER)) > > > > > > > > > > > > ? > > > > > > > > > > arm/arm64 do not select KVM_GUEST. Any kernel can be used for a guest, > > > > > and KVM/arm64 doesn't know about this configuration symbol. > > > > > > > > OK. > > > > > > > > Does PTP_1588_CLOCK_KVM need to default to yes? > > > > Perhaps only on X86, to maintain the status quo? > > > > > > I think I don't really understand the problem you are trying to > > > solve. Is it that 'make oldconfig' now asks you about this new driver? > > > Why is that an issue? > > > > My first "problem" was that it asked about this new driver on > > arm/arm64, while I assumed there were some missing dependencies > > (configuring a kernel should not ask useless questions). That turned > > out to be a wrong assumption, so there is no such problem here. > > > > The second problem is "default y": code that is not critical should > > not be enabled by default. Hence my last question. > > I think consistency between architectures is important. Certainly, > distributions depend on that, and we otherwise end-up with distro > kernels missing functionalities. > > The notion of "critical" is also pretty relative. defconfig contains a I'm not talking about defconfig, but about "default y" in defconfig. > gazillion of things that are not critical to most people, for example, > and yet misses a bunch of things that are needed to boot on some of my > systems. Perhaps those should be added, so those systems can be tested using defconfig? At least for arm64, I think that's aligned with the arm64 defconfig policy. > That's just to say that I find it difficult to make that choice from > the PoV of a kernel hacker. I'm personally more inclined to leave > things enabled and let people *disable* things if they want to reduce > the footprint of their kernel. The standard question to respond to w.r.t. "default y" is: "Why is your feature so special that it needs to be enabled by default?", which implies "default y" is the exception, not the rule. Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds 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=-8.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS 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 B2B2BC2B9F7 for ; Wed, 26 May 2021 08:51:05 +0000 (UTC) Received: from mm01.cs.columbia.edu (mm01.cs.columbia.edu [128.59.11.253]) by mail.kernel.org (Postfix) with ESMTP id 08A17613C0 for ; Wed, 26 May 2021 08:51:04 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 08A17613C0 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-m68k.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvmarm-bounces@lists.cs.columbia.edu Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 8A1E44A4A4; Wed, 26 May 2021 04:51:04 -0400 (EDT) X-Virus-Scanned: at lists.cs.columbia.edu Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 351aYq-uHgDK; Wed, 26 May 2021 04:51:03 -0400 (EDT) Received: from mm01.cs.columbia.edu (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 5606E49DE7; Wed, 26 May 2021 04:51:03 -0400 (EDT) Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id D6C684A483 for ; Wed, 26 May 2021 04:51:01 -0400 (EDT) X-Virus-Scanned: at lists.cs.columbia.edu Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id AysRMAu0jPz8 for ; Wed, 26 May 2021 04:50:59 -0400 (EDT) Received: from mail-ua1-f51.google.com (mail-ua1-f51.google.com [209.85.222.51]) by mm01.cs.columbia.edu (Postfix) with ESMTPS id 3EDB64064F for ; Wed, 26 May 2021 04:50:59 -0400 (EDT) Received: by mail-ua1-f51.google.com with SMTP id d14so353584ual.5 for ; Wed, 26 May 2021 01:50:59 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=ftj/o/FDlLZjvveU5gflHCydxVxy9/duOHSuWLsKuds=; b=UZmnsgl9i/IELoCP7CeDfQfPuZVdYOxGVjQ/LL0hCYD3xaTDXqEBJSgpIKKqqJNXLz 2g44PsYjt+P6gIMUwcMg9VI252h6JDXR9V3W4R+/gQVsLO1KAi+m2cqc55ki7FWqkwKU dTxTToJ6hxKQriM4a3NInW4vJkNFNY7ohTEc6RuR/YrDs4X9mkufCtd5HzJEDZ6ItvIL d3uIQzC/2swwC39A98h1vuAYQH38PA7L80siSREtv+1VcZId2UhLwZiFk0V+meHYqtj8 h95dUYLsbIdDvdYPYu2rAP2ET96g7aZ2DOL+xGULRYCi6H6vPevAg/fnZBwhB3gzVC77 DrOw== X-Gm-Message-State: AOAM5316Xn2aya9wXzUcY3ozE2fQJBfebk8K68KtnD4Zad/7FIdjPDdm EHDy3p8fQ6hT36H2bK3ckeLS7akgQPWaHXDVMck= X-Google-Smtp-Source: ABdhPJywUZ6Xwv+zij4MSQ000T5eibp+TpLy3YyyGoFqj+kf4ejbTke4WZLjWrCgAdHGlnISxwMlbpFtCE1QmEgp5j8= X-Received: by 2002:ab0:2a8b:: with SMTP id h11mr31904723uar.4.1622019058834; Wed, 26 May 2021 01:50:58 -0700 (PDT) MIME-Version: 1.0 References: <20210330145430.996981-1-maz@kernel.org> <20210330145430.996981-8-maz@kernel.org> <6c522f8116f54fa6f23a2d217d966c5a@kernel.org> <8735u9x6sb.wl-maz@kernel.org> <871r9tx5dq.wl-maz@kernel.org> In-Reply-To: <871r9tx5dq.wl-maz@kernel.org> From: Geert Uytterhoeven Date: Wed, 26 May 2021 10:50:47 +0200 Message-ID: Subject: Re: [PATCH v19 7/7] ptp: arm/arm64: Enable ptp_kvm for arm/arm64 To: Marc Zyngier Cc: KVM list , seanjc@google.com, Will Deacon , kvmarm@lists.cs.columbia.edu, Lorenzo Pieralisi , justin.he@arm.com, Steven Price , Android Kernel Team , Andre Przywara , Richard Cochran , Yangbo Lu , John Stultz , Thomas Gleixner , Linux ARM , netdev , Linux Kernel Mailing List , Sudeep Holla , Paolo Bonzini X-BeenThere: kvmarm@lists.cs.columbia.edu X-Mailman-Version: 2.1.14 Precedence: list List-Id: Where KVM/ARM decisions are made List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu Hi Marc, On Wed, May 26, 2021 at 10:32 AM Marc Zyngier wrote: > On Wed, 26 May 2021 09:18:27 +0100, > Geert Uytterhoeven wrote: > > On Wed, May 26, 2021 at 10:01 AM Marc Zyngier wrote: > > > On Wed, 26 May 2021 08:52:42 +0100, > > > Geert Uytterhoeven wrote: > > > > On Tue, May 11, 2021 at 11:13 AM Marc Zyngier wrote: > > > > > On 2021-05-11 10:07, Geert Uytterhoeven wrote: > > > > > > On Tue, Mar 30, 2021 at 4:56 PM Marc Zyngier wrote: > > > > > >> From: Jianyong Wu > > > > > > > > > > > >> --- a/drivers/ptp/Kconfig > > > > > >> +++ b/drivers/ptp/Kconfig > > > > > >> @@ -108,7 +108,7 @@ config PTP_1588_CLOCK_PCH > > > > > >> config PTP_1588_CLOCK_KVM > > > > > >> tristate "KVM virtual PTP clock" > > > > > >> depends on PTP_1588_CLOCK > > > > > >> - depends on KVM_GUEST && X86 > > > > > >> + depends on (KVM_GUEST && X86) || (HAVE_ARM_SMCCC_DISCOVERY && > > > > > >> ARM_ARCH_TIMER) > > > > > > > > > > > > Why does this not depend on KVM_GUEST on ARM? > > > > > > I.e. shouldn't the dependency be: > > > > > > > > > > > > KVM_GUEST && (X86 || (HAVE_ARM_SMCCC_DISCOVERY && ARM_ARCH_TIMER)) > > > > > > > > > > > > ? > > > > > > > > > > arm/arm64 do not select KVM_GUEST. Any kernel can be used for a guest, > > > > > and KVM/arm64 doesn't know about this configuration symbol. > > > > > > > > OK. > > > > > > > > Does PTP_1588_CLOCK_KVM need to default to yes? > > > > Perhaps only on X86, to maintain the status quo? > > > > > > I think I don't really understand the problem you are trying to > > > solve. Is it that 'make oldconfig' now asks you about this new driver? > > > Why is that an issue? > > > > My first "problem" was that it asked about this new driver on > > arm/arm64, while I assumed there were some missing dependencies > > (configuring a kernel should not ask useless questions). That turned > > out to be a wrong assumption, so there is no such problem here. > > > > The second problem is "default y": code that is not critical should > > not be enabled by default. Hence my last question. > > I think consistency between architectures is important. Certainly, > distributions depend on that, and we otherwise end-up with distro > kernels missing functionalities. > > The notion of "critical" is also pretty relative. defconfig contains a I'm not talking about defconfig, but about "default y" in defconfig. > gazillion of things that are not critical to most people, for example, > and yet misses a bunch of things that are needed to boot on some of my > systems. Perhaps those should be added, so those systems can be tested using defconfig? At least for arm64, I think that's aligned with the arm64 defconfig policy. > That's just to say that I find it difficult to make that choice from > the PoV of a kernel hacker. I'm personally more inclined to leave > things enabled and let people *disable* things if they want to reduce > the footprint of their kernel. The standard question to respond to w.r.t. "default y" is: "Why is your feature so special that it needs to be enabled by default?", which implies "default y" is the exception, not the rule. Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm 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=-9.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 AA9D9C2B9F7 for ; Wed, 26 May 2021 09:00:14 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 65B306128B for ; Wed, 26 May 2021 09:00:14 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 65B306128B Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-m68k.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:Cc:To:Subject:Message-ID:Date:From: In-Reply-To:References:MIME-Version:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=gvHuQJL1Vgwx0ezgK4J4Y6LiTNZJmG3GIN0B8aIRX1k=; b=yi9h4QzxHB0gsw DCUjZoSEwVf1/PHnLF1fcOEeJlzqVnBGnRiijJ/1gMfaJ4MlUtVQueenXp/mb9KDpZ5d4FV1hBvxt jm42b6YjCzILXpikhUi3u9RfViRnOnomj146UAyH1L239xzTsB5wu6zxP7yJVRObvDEnyIXTJxXgt hPcBw1b0l5NnBUdbIscf4/vpMIPA/7WZ1KdlJ6EL415+/oCJmSg+hAbOlF+5R/FUXqZcdllQJEtQ5 s5crB+fyI95C0rWxXuQ08YQH7MawLhenb11Tr8H9EvxUKr3nkCK6tY0smbkYgCmzpxuPt5tISYw7H ZIc5kvtO74dow640FS7A==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1llpMc-00Cfqu-L5; Wed, 26 May 2021 08:58:08 +0000 Received: from mail-ua1-f51.google.com ([209.85.222.51]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1llpFl-00Ccno-5r for linux-arm-kernel@lists.infradead.org; Wed, 26 May 2021 08:51:02 +0000 Received: by mail-ua1-f51.google.com with SMTP id v27so344837uat.12 for ; Wed, 26 May 2021 01:50:59 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=ftj/o/FDlLZjvveU5gflHCydxVxy9/duOHSuWLsKuds=; b=YjcvrrZbcP74MpPXzMe36pzYysvTv7qdckxpCit/6g+Hl0S1t7UdTZWwZyEjqXGeuH YKOAtO4pVwXhRXFZhm0CbPRia7HGUtS6QtmqAkJxEgCAcMPY29HRjSelRlqabtz+oFt4 x19jCadCA0xlj/lc//gbVfoGpQ98D/ZpsZ9pRUpQybPoj3ihlwT6hraycaB6cknVFMV3 tk9FC5gIOPSzER0RPq9vbKsMgNeh9/zmiTzQ2RD45kS0cNeybqcqpgLUZ5Fi8XVKPWg7 iA6iDPPXOH/fXmmT1uBxX0EW95H7NKTV2YDsH7ujBgbSOr6G5CioKejBwCT9dB4Abuz6 8AZA== X-Gm-Message-State: AOAM533Fmaysg9L3wCPCPBnNbjMhB4/aKS0ind+qj8XJLV7wnGLq+2Zp LyPeD1/TDr0821bsofzlgZouGy0l7wqtjGA2nMU= X-Google-Smtp-Source: ABdhPJywUZ6Xwv+zij4MSQ000T5eibp+TpLy3YyyGoFqj+kf4ejbTke4WZLjWrCgAdHGlnISxwMlbpFtCE1QmEgp5j8= X-Received: by 2002:ab0:2a8b:: with SMTP id h11mr31904723uar.4.1622019058834; Wed, 26 May 2021 01:50:58 -0700 (PDT) MIME-Version: 1.0 References: <20210330145430.996981-1-maz@kernel.org> <20210330145430.996981-8-maz@kernel.org> <6c522f8116f54fa6f23a2d217d966c5a@kernel.org> <8735u9x6sb.wl-maz@kernel.org> <871r9tx5dq.wl-maz@kernel.org> In-Reply-To: <871r9tx5dq.wl-maz@kernel.org> From: Geert Uytterhoeven Date: Wed, 26 May 2021 10:50:47 +0200 Message-ID: Subject: Re: [PATCH v19 7/7] ptp: arm/arm64: Enable ptp_kvm for arm/arm64 To: Marc Zyngier Cc: jianyong.wu@arm.com, netdev , Yangbo Lu , John Stultz , Thomas Gleixner , Paolo Bonzini , seanjc@google.com, Richard Cochran , Mark Rutland , Will Deacon , Suzuki K Poulose , Andre Przywara , Steven Price , Lorenzo Pieralisi , Sudeep Holla , Linux Kernel Mailing List , Linux ARM , kvmarm@lists.cs.columbia.edu, KVM list , Steve Capper , justin.he@arm.com, Android Kernel Team X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210526_015101_274988_B062AB38 X-CRM114-Status: GOOD ( 45.06 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi Marc, On Wed, May 26, 2021 at 10:32 AM Marc Zyngier wrote: > On Wed, 26 May 2021 09:18:27 +0100, > Geert Uytterhoeven wrote: > > On Wed, May 26, 2021 at 10:01 AM Marc Zyngier wrote: > > > On Wed, 26 May 2021 08:52:42 +0100, > > > Geert Uytterhoeven wrote: > > > > On Tue, May 11, 2021 at 11:13 AM Marc Zyngier wrote: > > > > > On 2021-05-11 10:07, Geert Uytterhoeven wrote: > > > > > > On Tue, Mar 30, 2021 at 4:56 PM Marc Zyngier wrote: > > > > > >> From: Jianyong Wu > > > > > > > > > > > >> --- a/drivers/ptp/Kconfig > > > > > >> +++ b/drivers/ptp/Kconfig > > > > > >> @@ -108,7 +108,7 @@ config PTP_1588_CLOCK_PCH > > > > > >> config PTP_1588_CLOCK_KVM > > > > > >> tristate "KVM virtual PTP clock" > > > > > >> depends on PTP_1588_CLOCK > > > > > >> - depends on KVM_GUEST && X86 > > > > > >> + depends on (KVM_GUEST && X86) || (HAVE_ARM_SMCCC_DISCOVERY && > > > > > >> ARM_ARCH_TIMER) > > > > > > > > > > > > Why does this not depend on KVM_GUEST on ARM? > > > > > > I.e. shouldn't the dependency be: > > > > > > > > > > > > KVM_GUEST && (X86 || (HAVE_ARM_SMCCC_DISCOVERY && ARM_ARCH_TIMER)) > > > > > > > > > > > > ? > > > > > > > > > > arm/arm64 do not select KVM_GUEST. Any kernel can be used for a guest, > > > > > and KVM/arm64 doesn't know about this configuration symbol. > > > > > > > > OK. > > > > > > > > Does PTP_1588_CLOCK_KVM need to default to yes? > > > > Perhaps only on X86, to maintain the status quo? > > > > > > I think I don't really understand the problem you are trying to > > > solve. Is it that 'make oldconfig' now asks you about this new driver? > > > Why is that an issue? > > > > My first "problem" was that it asked about this new driver on > > arm/arm64, while I assumed there were some missing dependencies > > (configuring a kernel should not ask useless questions). That turned > > out to be a wrong assumption, so there is no such problem here. > > > > The second problem is "default y": code that is not critical should > > not be enabled by default. Hence my last question. > > I think consistency between architectures is important. Certainly, > distributions depend on that, and we otherwise end-up with distro > kernels missing functionalities. > > The notion of "critical" is also pretty relative. defconfig contains a I'm not talking about defconfig, but about "default y" in defconfig. > gazillion of things that are not critical to most people, for example, > and yet misses a bunch of things that are needed to boot on some of my > systems. Perhaps those should be added, so those systems can be tested using defconfig? At least for arm64, I think that's aligned with the arm64 defconfig policy. > That's just to say that I find it difficult to make that choice from > the PoV of a kernel hacker. I'm personally more inclined to leave > things enabled and let people *disable* things if they want to reduce > the footprint of their kernel. The standard question to respond to w.r.t. "default y" is: "Why is your feature so special that it needs to be enabled by default?", which implies "default y" is the exception, not the rule. Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel