linux-kernel - Re: [PATCH v2 0/5] x86: Cleanups around slow_down

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Message-ID: <3102d712-8fa7-4567-bb8a-0f39fd71712d@suse.com>
Date: Fri, 9 Jan 2026 13:07:57 +0100
From: Juergen Gross <jgross@...e.com>
To: linux-kernel@...r.kernel.org, x86@...nel.org,
 virtualization@...ts.linux.dev, kvm@...r.kernel.org,
 linux-block@...r.kernel.org
Cc: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
 Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>,
 "H. Peter Anvin" <hpa@...or.com>, Ajay Kaher <ajay.kaher@...adcom.com>,
 Alexey Makhalov <alexey.makhalov@...adcom.com>,
 Broadcom internal kernel review list
 <bcm-kernel-feedback-list@...adcom.com>, Paolo Bonzini
 <pbonzini@...hat.com>, Vitaly Kuznetsov <vkuznets@...hat.com>,
 Boris Ostrovsky <boris.ostrovsky@...cle.com>,
 xen-devel@...ts.xenproject.org, Denis Efremov <efremov@...ux.com>,
 Jens Axboe <axboe@...nel.dk>
Subject: Re: [PATCH v2 0/5] x86: Cleanups around slow_down_io()

Gentle ping.

On 16.12.25 14:41, Juergen Gross wrote:
> While looking at paravirt cleanups I stumbled over slow_down_io() and
> the related REALLY_SLOW_IO define.
> 
> Do several cleanups, resulting in a deletion of REALLY_SLOW_IO and the
> io_delay() paravirt function hook.
> 
> Patch 4 is removing the config options for selecting the default delay
> mechanism and sets the default to "no delay". This is in preparation of
> removing the io_delay() functionality completely, as suggested by Ingo
> Molnar.
> 
> Patch 5 is adding an additional config option allowing to avoid
> building io_delay.c (default is still to build it).
> 
> Changes in V2:
> - patches 2 and 3 of V1 have been applied
> - new patches 4 and 5
> 
> Juergen Gross (5):
>    x86/paravirt: Replace io_delay() hook with a bool
>    block/floppy: Don't use REALLY_SLOW_IO for delays
>    x86/io: Remove REALLY_SLOW_IO handling
>    x86/io_delay: Switch io_delay() default mechanism to "none"
>    x86/io_delay: Add config option for controlling build of io_delay.
> 
>   arch/x86/Kconfig                      |  8 +++
>   arch/x86/Kconfig.debug                | 30 ----------
>   arch/x86/include/asm/floppy.h         | 31 ++++++++--
>   arch/x86/include/asm/io.h             | 17 +++---
>   arch/x86/include/asm/paravirt.h       | 11 +---
>   arch/x86/include/asm/paravirt_types.h |  3 +-
>   arch/x86/kernel/Makefile              |  3 +-
>   arch/x86/kernel/cpu/vmware.c          |  2 +-
>   arch/x86/kernel/io_delay.c            | 81 +--------------------------
>   arch/x86/kernel/kvm.c                 |  8 +--
>   arch/x86/kernel/paravirt.c            |  3 +-
>   arch/x86/kernel/setup.c               |  4 +-
>   arch/x86/xen/enlighten_pv.c           |  6 +-
>   drivers/block/floppy.c                |  2 -
>   14 files changed, 55 insertions(+), 154 deletions(-)
> 

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