From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B40FE2609CC; Sun, 14 Dec 2025 08:05:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765699517; cv=none; b=K3Ad1BPogopym3/to1czJhe8+AzlbH9x1f8oATk9aRsrcOR3jgGSkXkdroDT5H5+7fED2HTf5W5kj+YrEJhK5LfleyPe9+RTWecfmKozlq38/11WjADQrNIN7lX/Zc/kKb82W/+KuV1XQffHMaw+q9+uYsSjM7KgYPI494Jn+lU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765699517; c=relaxed/simple; bh=ihizdAs5xDOev8/N37y8juDMqohuVvatea37UyTaRi8=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=coAzTKlhyGaf9iurBjOf2YcFG1tIDZRAxvVQ5y0PIJRXEcTsHfT/j1znpNZ1lqfMyKBiIS4pKWxCy72vQpMJXZnMiOtc9aGvvGMs7gdQroeMfbqduoGwl8igRJYSnLTRpix5Q2VKvstKFeKyDyem3s+I6aJfM6vI0czfsQ3QyaU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Kty6VVwz; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Kty6VVwz" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 66711C4CEF1; Sun, 14 Dec 2025 08:05:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1765699517; bh=ihizdAs5xDOev8/N37y8juDMqohuVvatea37UyTaRi8=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Kty6VVwzTJtdeGkn/OL/sk2f7Vfnpv82H2rJ71SoVx5wLW/jb8lxm2RuFqMqpcEHB 9/ooTAhhdffBRwzl0rkjmLIVGEm8RBGaGHTqlxjBo6IhmNSozd/xIqpYfSV3HiEEuF r9Ae5LH2yKrVwPDJsSlCF5IKvD6QnlpE6J1sYr19zntuAY/UyUwqETaiphNCCl6Fg0 OIfJqqcMaGaTZTfwoSpZdnCgyFEicpt76KiSaP7TH5N3yFXQRgkZp5SQtveJKUU8O8 qy/urqiNHzU11rrcFzoWeK/Trun7TjKtaJPlRq9DNhHOtzui8DMkvIIYEGKRnYClqr 1Dx2GzcDYarcA== Date: Sun, 14 Dec 2025 09:05:09 +0100 From: Ingo Molnar To: Juergen Gross Cc: linux-kernel@vger.kernel.org, x86@kernel.org, virtualization@lists.linux.dev, kvm@vger.kernel.org, linux-hwmon@vger.kernel.org, linux-block@vger.kernel.org, Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , Ajay Kaher , Alexey Makhalov , Broadcom internal kernel review list , Paolo Bonzini , Vitaly Kuznetsov , Boris Ostrovsky , xen-devel@lists.xenproject.org, Jean Delvare , Guenter Roeck , Denis Efremov , Jens Axboe Subject: Re: [PATCH 0/5] x86: Cleanups around slow_down_io() Message-ID: References: <20251126162018.5676-1-jgross@suse.com> Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20251126162018.5676-1-jgross@suse.com> * Juergen Gross wrote: > While looking at paravirt cleanups I stumbled over slow_down_io() and > the related REALLY_SLOW_IO define. > > Especially REALLY_SLOW_IO is a mess, which is proven by 2 completely > wrong use cases. > > Do several cleanups, resulting in a deletion of REALLY_SLOW_IO and the > io_delay() paravirt function hook. > > Patches 2 and 3 are not changing any functionality, but maybe they > should? As the potential bug has been present for more than a decade > now, I went with just deleting the useless "#define REALLY_SLOW_IO". > The alternative would be to do something similar as in patch 5. > > Juergen Gross (5): > x86/paravirt: Replace io_delay() hook with a bool > hwmon/lm78: Drop REALLY_SLOW_IO setting > hwmon/w83781d: Drop REALLY_SLOW_IO setting > block/floppy: Don't use REALLY_SLOW_IO for delays > x86/io: Remove REALLY_SLOW_IO handling > > arch/x86/include/asm/floppy.h | 27 ++++++++++++++++++++++----- > arch/x86/include/asm/io.h | 12 +++++------- > arch/x86/include/asm/paravirt.h | 11 +---------- > arch/x86/include/asm/paravirt_types.h | 3 +-- > arch/x86/kernel/cpu/vmware.c | 2 +- > arch/x86/kernel/kvm.c | 8 +------- > arch/x86/kernel/paravirt.c | 3 +-- > arch/x86/xen/enlighten_pv.c | 6 +----- > drivers/block/floppy.c | 2 -- > drivers/hwmon/lm78.c | 5 +++-- > drivers/hwmon/w83781d.c | 5 +++-- > 11 files changed, 39 insertions(+), 45 deletions(-) I think we should get rid of *all* io_delay hacks, they might have been relevant in the days of i386 systems, but we don't even support i386 CPUs anymore. Should it cause any regressions, it's easy to bisect to. There's been enough changes around all these facilities that the original timings are probably way off already, so we've just been cargo-cult porting these to newer kernels essentially. Thanks, Ingo