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

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Message-ID: <20251216134150.2710-1-jgross@suse.com>
Date: Tue, 16 Dec 2025 14:41:44 +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: Juergen Gross <jgross@...e.com>,
	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: [PATCH v2 0/5] x86: Cleanups around slow_down_io()

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(-)

-- 
2.51.0